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1
Puthiyaveetil, Sujith, and John F. Allen. "Chloroplast two-component systems: evolution of the link between photosynthesis and gene expression." Proceedings of the Royal Society B: Biological Sciences 276, no. 1665 (February 25, 2009): 2133–45. http://dx.doi.org/10.1098/rspb.2008.1426.
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Two-component signal transduction, consisting of sensor kinases and response regulators, is the predominant signalling mechanism in bacteria. This signalling system originated in prokaryotes and has spread throughout the eukaryotic domain of life through endosymbiotic, lateral gene transfer from the bacterial ancestors and early evolutionary precursors of eukaryotic, cytoplasmic, bioenergetic organelles—chloroplasts and mitochondria. Until recently, it was thought that two-component systems inherited from an ancestral cyanobacterial symbiont are no longer present in chloroplasts. Recent research now shows that two-component systems have survived in chloroplasts as products of both chloroplast and nuclear genes. Comparative genomic analysis of photosynthetic eukaryotes shows a lineage-specific distribution of chloroplast two-component systems. The components and the systems they comprise have homologues in extant cyanobacterial lineages, indicating their ancient cyanobacterial origin. Sequence and functional characteristics of chloroplast two-component systems point to their fundamental role in linking photosynthesis with gene expression. We propose that two-component systems provide a coupling between photosynthesis and gene expression that serves to retain genes in chloroplasts, thus providing the basis of cytoplasmic, non-Mendelian inheritance of plastid-associated characters. We discuss the role of this coupling in the chronobiology of cells and in the dialogue between nuclear and cytoplasmic genetic systems.
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Nikkanen, Lauri, and Eevi Rintamäki. "Chloroplast thioredoxin systems dynamically regulate photosynthesis in plants." Biochemical Journal 476, no. 7 (April 15, 2019): 1159–72. http://dx.doi.org/10.1042/bcj20180707.
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Abstract Photosynthesis is a highly regulated process in photoautotrophic cells. The main goal of the regulation is to keep the basic photosynthetic reactions, i.e. capturing light energy, conversion into chemical energy and production of carbohydrates, in balance. The rationale behind the evolution of strong regulation mechanisms is to keep photosynthesis functional under all conditions encountered by sessile plants during their lifetimes. The regulatory mechanisms may, however, also impair photosynthetic efficiency by overriding the photosynthetic reactions in controlled environments like crop fields or bioreactors, where light energy could be used for production of sugars instead of dissipation as heat and down-regulation of carbon fixation. The plant chloroplast has a high number of regulatory proteins called thioredoxins (TRX), which control the function of chloroplasts from biogenesis and assembly of chloroplast machinery to light and carbon fixation reactions as well as photoprotective mechanisms. Here, we review the current knowledge of regulation of photosynthesis by chloroplast TRXs and assess the prospect of improving plant photosynthetic efficiency by modification of chloroplast thioredoxin systems.
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Gan, Ping, Fang Liu, Rongbai Li, Shaokui Wang, and Jijing Luo. "Chloroplasts— Beyond Energy Capture and Carbon Fixation: Tuning of Photosynthesis in Response to Chilling Stress." International Journal of Molecular Sciences 20, no. 20 (October 11, 2019): 5046. http://dx.doi.org/10.3390/ijms20205046.
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As organelles for photosynthesis in green plants, chloroplasts play a vital role in solar energy capture and carbon fixation. The maintenance of normal chloroplast physiological functions is essential for plant growth and development. Low temperature is an adverse environmental stress that affects crop productivity. Low temperature severely affects the growth and development of plants, especially photosynthesis. To date, many studies have reported that chloroplasts are not only just organelles of photosynthesis. Chloroplasts can also perceive chilling stress signals via membranes and photoreceptors, and they maintain their homeostasis and promote photosynthesis by regulating the state of lipid membranes, the abundance of photosynthesis-related proteins, the activity of enzymes, the redox state, and the balance of hormones and by releasing retrograde signals, thus improving plant resistance to low temperatures. This review focused on the potential functions of chloroplasts in fine tuning photosynthesis processes under low-temperature stress by perceiving stress signals, modulating the expression of photosynthesis-related genes, and scavenging excess reactive oxygen species (ROS) in chloroplasts to survive the adverse environment.
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Trotta, Andrea, Moona Rahikainen, Grzegorz Konert, Giovanni Finazzi, and Saijaliisa Kangasjärvi. "Signalling crosstalk in light stress and immune reactions in plants." Philosophical Transactions of the Royal Society B: Biological Sciences 369, no. 1640 (April 19, 2014): 20130235. http://dx.doi.org/10.1098/rstb.2013.0235.
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The evolutionary history of plants is tightly connected with the evolution of microbial pathogens and herbivores, which use photosynthetic end products as a source of life. In these interactions, plants, as the stationary party, have evolved sophisticated mechanisms to sense, signal and respond to the presence of external stress agents. Chloroplasts are metabolically versatile organelles that carry out fundamental functions in determining appropriate immune reactions in plants. Besides photosynthesis, chloroplasts host key steps in the biosynthesis of amino acids, stress hormones and secondary metabolites, which have a great impact on resistance against pathogens and insect herbivores. Changes in chloroplast redox signalling pathways and reactive oxygen species metabolism also mediate local and systemic signals, which modulate plant resistance to light stress and disease. Moreover, interplay among chloroplastic signalling networks and plasma membrane receptor kinases is emerging as a key mechanism that modulates stress responses in plants. This review highlights the central role of chloroplasts in the signalling crosstalk that essentially determines the outcome of plant–pathogen interactions in plants.
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Voon, Chia Pao, Xiaoqian Guan, Yuzhe Sun, Abira Sahu, May Ngor Chan, Per Gardeström, Stephan Wagner, et al. "ATP compartmentation in plastids and cytosol ofArabidopsis thalianarevealed by fluorescent protein sensing." Proceedings of the National Academy of Sciences 115, no. 45 (October 23, 2018): E10778—E10787. http://dx.doi.org/10.1073/pnas.1711497115.
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Matching ATP:NADPH provision and consumption in the chloroplast is a prerequisite for efficient photosynthesis. In terms of ATP:NADPH ratio, the amount of ATP generated from the linear electron flow does not meet the demand of the Calvin–Benson–Bassham (CBB) cycle. Several different mechanisms to increase ATP availability have evolved, including cyclic electron flow in higher plants and the direct import of mitochondrial-derived ATP in diatoms. By imaging a fluorescent ATP sensor protein expressed in livingArabidopsis thalianaseedlings, we found that MgATP2−concentrations were lower in the stroma of mature chloroplasts than in the cytosol, and exogenous ATP was able to enter chloroplasts isolated from 4- and 5-day-old seedlings, but not chloroplasts isolated from 10- or 20-day-old photosynthetic tissues. This observation is in line with the previous finding that the expression of chloroplast nucleotide transporters (NTTs) inArabidopsismesophyll is limited to very young seedlings. Employing a combination of photosynthetic and respiratory inhibitors with compartment-specific imaging of ATP, we corroborate the dependency of stromal ATP production on mitochondrial dissipation of photosynthetic reductant. Our data suggest that, during illumination, the provision and consumption of ATP:NADPH in chloroplasts can be balanced by exporting excess reductants rather than importing ATP from the cytosol.
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Lie, Guang Hua, and Gan Wen Lie. "Measure of the Photosynthetic Efficiency of the Cabbage Leaves by Using Photo-Acoustic Tomography Spectroscopy Technology." Advanced Materials Research 399-401 (November 2011): 2283–87. http://dx.doi.org/10.4028/www.scientific.net/amr.399-401.2283.
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By using a new type of photo-acoustic tomography spectroscopy with non-damage and weak signals detection, the normalized photo-acoustic tomography spectroscopy (PAS-CT) and optical absorption characteristic of the green and yellow leaves of the cabbage are measured. The results show that: the leaves of the cabbage could get different levels of photo-acoustic spectroscopy from different chopping frequency. The chloroplast number in the yellow leaves was less than that in the green leaves, so the photosynthesis in the yellow leaves was significantly weakened compared with the green leaves. The more the chloroplast number in the cabbage leaves were, the stronger the photosynthesis was and the higher the photosynthetic efficiency was. The chopping frequency of 24Hz could activate more chloroplasts than 34Hz and improve the photosynthetic efficiency of the cabbage leaves. What’s more, it could improve the yield of cabbage. Photo-acoustic tomography spectroscopy is a new way of studying photosynthesis. It has a bright and far-reaching future.
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Kroh, Gretchen E., and Marinus Pilon. "Regulation of Iron Homeostasis and Use in Chloroplasts." International Journal of Molecular Sciences 21, no. 9 (May 11, 2020): 3395. http://dx.doi.org/10.3390/ijms21093395.
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Iron (Fe) is essential for life because of its role in protein cofactors. Photosynthesis, in particular photosynthetic electron transport, has a very high demand for Fe cofactors. Fe is commonly limiting in the environment, and therefore photosynthetic organisms must acclimate to Fe availability and avoid stress associated with Fe deficiency. In plants, adjustment of metabolism, of Fe utilization, and gene expression, is especially important in the chloroplasts during Fe limitation. In this review, we discuss Fe use, Fe transport, and mechanisms of acclimation to Fe limitation in photosynthetic lineages with a focus on the photosynthetic electron transport chain. We compare Fe homeostasis in Cyanobacteria, the evolutionary ancestors of chloroplasts, with Fe homeostasis in green algae and in land plants in order to provide a deeper understanding of how chloroplasts and photosynthesis may cope with Fe limitation.
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Piippo, Mirva, Yagut Allahverdiyeva, Virpi Paakkarinen, Ulla-Maija Suoranta, Natalia Battchikova, and Eva-Mari Aro. "Chloroplast-mediated regulation of nuclear genes in Arabidopsis thaliana in the absence of light stress." Physiological Genomics 25, no. 1 (March 13, 2006): 142–52. http://dx.doi.org/10.1152/physiolgenomics.00256.2005.
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Chloroplast signaling involves mechanisms to relay information from chloroplasts to the nucleus, to change nuclear gene expression in response to environmental cues. Aside from reactive oxygen species (ROS) produced under stress conditions, changes in the reduction/oxidation state of photosynthetic electron transfer components or coupled compounds in the stroma and the accumulation of photosynthesis-derived metabolites are likely origins of chloroplast signals. We attempted to investigate the origin of the signals from chloroplasts in mature Arabidopsis leaves by differentially modulating the redox states of the plastoquinone pool and components on the reducing side of photosystem I, as well as the rate of CO2 fixation, while avoiding the production of ROS by excess light. Differential expression of several nuclear photosynthesis genes, including a set of Calvin cycle enzymes, was recorded. These responded to the stromal redox conditions under prevailing light conditions but were independent of the redox state of the plastoquinone pool. The steady-state CO2 fixation rate was reflected in the orchestration of the expression of a number of genes encoding cytoplasmic proteins, including several glycolysis genes and the trehalose-6-phosphate synthase gene, and also the chloroplast-targeted chaperone DnaJ. Clearly, in mature leaves, the redox state of the compounds on the reducing side of photosystem I is of greater importance in light-dependent modulation of nuclear gene expression than the redox state of the plastoquinone pool, particularly at early signaling phases. It also became apparent that photosynthesis-mediated generation of metabolites or signaling molecules is involved in the relay of information from chloroplast to nucleus.
9
Lu, Yan, and Jian Yao. "Chloroplasts at the Crossroad of Photosynthesis, Pathogen Infection and Plant Defense." International Journal of Molecular Sciences 19, no. 12 (December 5, 2018): 3900. http://dx.doi.org/10.3390/ijms19123900.
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Photosynthesis, pathogen infection, and plant defense are three important biological processes that have been investigated separately for decades. Photosynthesis generates ATP, NADPH, and carbohydrates. These resources are utilized for the synthesis of many important compounds, such as primary metabolites, defense-related hormones abscisic acid, ethylene, jasmonic acid, and salicylic acid, and antimicrobial compounds. In plants and algae, photosynthesis and key steps in the synthesis of defense-related hormones occur in chloroplasts. In addition, chloroplasts are major generators of reactive oxygen species and nitric oxide, and a site for calcium signaling. These signaling molecules are essential to plant defense as well. All plants grown naturally are attacked by pathogens. Bacterial pathogens enter host tissues through natural openings or wounds. Upon invasion, bacterial pathogens utilize a combination of different virulence factors to suppress host defense and promote pathogenicity. On the other hand, plants have developed elaborate defense mechanisms to protect themselves from pathogen infections. This review summarizes recent discoveries on defensive roles of signaling molecules made by plants (primarily in their chloroplasts), counteracting roles of chloroplast-targeted effectors and phytotoxins elicited by bacterial pathogens, and how all these molecules crosstalk and regulate photosynthesis, pathogen infection, and plant defense, using chloroplasts as a major battlefield.
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Blanco, Nicolás E., Manuel Guinea-Díaz, James Whelan, and Åsa Strand. "Interaction between plastid and mitochondrial retrograde signalling pathways during changes to plastid redox status." Philosophical Transactions of the Royal Society B: Biological Sciences 369, no. 1640 (April 19, 2014): 20130231. http://dx.doi.org/10.1098/rstb.2013.0231.
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Mitochondria and chloroplasts depend upon each other; photosynthesis provides substrates for mitochondrial respiration and mitochondrial metabolism is essential for sustaining photosynthetic carbon assimilation. In addition, mitochondrial respiration protects photosynthesis against photoinhibition by dissipating excess redox equivalents from the chloroplasts. Genetic defects in mitochondrial function result in an excessive reduction and energization of the chloroplast. Thus, it is clear that the activities of mitochondria and plastids need to be coordinated, but the manner by which the organelles communicate to coordinate their activities is unknown. The regulator of alternative oxidase ( rao1) mutant was isolated as a mutant unable to induce AOX1a expression in response to the inhibitor of the mitochondrial cytochrome c reductase (complex III), antimycin A. RAO1 encodes the nuclear localized cyclin-dependent kinase E1 (CDKE1). Interestingly, the rao1 mutant demonstrates a genome uncoupled phenotype also in response to redox changes in the photosynthetic electron transport chain. Thus, CDKE1 was shown to regulate both LIGHT HARVESTING COMPLEX B ( LHCB ) and ALTERNATIVE OXIDASE 1 ( AOX1a ) expression in response to retrograde signals. Our results suggest that CDKE1 is a central nuclear component integrating mitochondrial and plastid retrograde signals and plays a role in regulating energy metabolism during the response to stress.
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Llorente, Briardo, Salvador Torres-Montilla, Luca Morelli, Igor Florez-Sarasa, José Tomás Matus, Miguel Ezquerro, Lucio D’Andrea, et al. "Synthetic conversion of leaf chloroplasts into carotenoid-rich plastids reveals mechanistic basis of natural chromoplast development." Proceedings of the National Academy of Sciences 117, no. 35 (August 19, 2020): 21796–803. http://dx.doi.org/10.1073/pnas.2004405117.
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Plastids, the defining organelles of plant cells, undergo physiological and morphological changes to fulfill distinct biological functions. In particular, the differentiation of chloroplasts into chromoplasts results in an enhanced storage capacity for carotenoids with industrial and nutritional value such as beta-carotene (provitamin A). Here, we show that synthetically inducing a burst in the production of phytoene, the first committed intermediate of the carotenoid pathway, elicits an artificial chloroplast-to-chromoplast differentiation in leaves. Phytoene overproduction initially interferes with photosynthesis, acting as a metabolic threshold switch mechanism that weakens chloroplast identity. In a second stage, phytoene conversion into downstream carotenoids is required for the differentiation of chromoplasts, a process that involves a concurrent reprogramming of nuclear gene expression and plastid morphology for improved carotenoid storage. We hence demonstrate that loss of photosynthetic competence and enhanced production of carotenoids are not just consequences but requirements for chloroplasts to differentiate into chromoplasts.
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Foyer, Christine H., Barbara Karpinska, and Karin Krupinska. "The functions of WHIRLY1 and REDOX-RESPONSIVE TRANSCRIPTION FACTOR 1 in cross tolerance responses in plants: a hypothesis." Philosophical Transactions of the Royal Society B: Biological Sciences 369, no. 1640 (April 19, 2014): 20130226. http://dx.doi.org/10.1098/rstb.2013.0226.
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Chloroplasts are important sensors of environment change, fulfilling key roles in the regulation of plant growth and development in relation to environmental cues. Photosynthesis produces a repertoire of reductive and oxidative (redox) signals that provide information to the nucleus facilitating appropriate acclimation to a changing light environment. Redox signals are also recognized by the cellular innate immune system allowing activation of non-specific, stress-responsive pathways that underpin cross tolerance to biotic–abiotic stresses. While these pathways have been intensively studied in recent years, little is known about the different components that mediate chloroplast-to-nucleus signalling and facilitate cross tolerance phenomena. Here, we consider the properties of the WHIRLY family of proteins and the REDOX-RESPONSIVE TRANSCRIPTION FACTOR 1 (RRTF1) in relation to chloroplast redox signals that facilitate the synergistic co-activation of gene expression pathways and confer cross tolerance to abiotic and biotic stresses. We propose a new hypothesis for the role of WHIRLY1 as a redox sensor in chloroplast-to-nucleus retrograde signalling leading to cross tolerance, including acclimation and immunity responses. By virtue of its association with chloroplast nucleoids and with nuclear DNA, WHIRLY1 is an attractive candidate coordinator of the expression of photosynthetic genes in the nucleus and chloroplasts. We propose that the redox state of the photosynthetic electron transport chain triggers the movement of WHIRLY1 from the chloroplasts to the nucleus, and draw parallels with the regulation of NONEXPRESSOR OF PATHOGENESIS-RELATED GENES 1 (NPR1).
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Serôdio, João, Sónia Cruz, Paulo Cartaxana, and Ricardo Calado. "Photophysiology of kleptoplasts: photosynthetic use of light by chloroplasts living in animal cells." Philosophical Transactions of the Royal Society B: Biological Sciences 369, no. 1640 (April 19, 2014): 20130242. http://dx.doi.org/10.1098/rstb.2013.0242.
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Kleptoplasty is a remarkable type of photosynthetic association, resulting from the maintenance of functional chloroplasts—the ‘kleptoplasts’—in the tissues of a non-photosynthetic host. It represents a biologically unique condition for chloroplast and photosynthesis functioning, occurring in different phylogenetic lineages, namely dinoflagellates, ciliates, foraminiferans and, most interestingly, a single taxon of metazoans, the sacoglossan sea slugs. In the case of sea slugs, chloroplasts from macroalgae are often maintained as intracellular organelles in cells of these marine gastropods, structurally intact and photosynthetically competent for extended periods of time. Kleptoplasty has long attracted interest owing to the longevity of functional kleptoplasts in the absence of the original algal nucleus and the limited number of proteins encoded by the chloroplast genome. This review updates the state-of-the-art on kleptoplast photophysiology, focusing on the comparative analysis of the responses to light of the chloroplasts when in their original, macroalgal cells, and when sequestered in animal cells and functioning as kleptoplasts. It covers fundamental but ecologically relevant aspects of kleptoplast light responses, such as the occurrence of photoacclimation in hospite , operation of photoprotective processes and susceptibility to photoinhibition. Emphasis is given to host-mediated processes unique to kleptoplastic associations, reviewing current hypotheses on behavioural photoprotection and host-mediated enhancement of photosynthetic performance, and identifying current gaps in sacoglossan kleptoplast photophysiology research.
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Chen, Silin, Ping Li, Shunling Tan, Xiaojun Pu, Ying Zhou, Keming Hu, Wei Huang, and Li Liu. "Combined Proteomic and Physiological Analysis of Chloroplasts Reveals Drought and Recovery Response Mechanisms in Nicotiana benthamiana." Plants 10, no. 6 (June 2, 2021): 1127. http://dx.doi.org/10.3390/plants10061127.
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Chloroplasts play essential roles in plant metabolic processes and stress responses by functioning as environmental sensors. Understanding chloroplast responses to drought stress and subsequent recovery will help the ability to improve stress tolerance in plants. Here, a combined proteomic and physiological approach was used to investigate the response mechanisms of Nicotiana benthamiana chloroplasts to drought stress and subsequent recovery. Early in the stress response, changes in stomatal movement were accompanied by immediate changes in protein synthesis to sustain the photosynthetic process. Thereafter, increasing drought stress seriously affected photosynthetic efficiency and led to altered expression of photosynthesis- and carbon-fixation-related proteins to protect the plants against photo-oxidative damage. Additional repair mechanisms were activated at the early stage of recovery to restore physiological functions and repair drought-induced damages, even while the negative effects of drought stress were still ongoing. Prolonging the re-watering period led to the gradual recovery of photosynthesis at both physiological and protein levels, indicating that a long repair process is required to restore plant function. Our findings provide a precise view of drought and recovery response mechanisms in N. benthamiana and serve as a reference for further investigation into the physiological and molecular mechanisms underlying plant drought tolerance.
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Zhang, Yi, Aihong Zhang, Xiuming Li, and Congming Lu. "The Role of Chloroplast Gene Expression in Plant Responses to Environmental Stress." International Journal of Molecular Sciences 21, no. 17 (August 24, 2020): 6082. http://dx.doi.org/10.3390/ijms21176082.
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Chloroplasts are plant organelles that carry out photosynthesis, produce various metabolites, and sense changes in the external environment. Given their endosymbiotic origin, chloroplasts have retained independent genomes and gene-expression machinery. Most genes from the prokaryotic ancestors of chloroplasts were transferred into the nucleus over the course of evolution. However, the importance of chloroplast gene expression in environmental stress responses have recently become more apparent. Here, we discuss the emerging roles of the distinct chloroplast gene expression processes in plant responses to environmental stresses. For example, the transcription and translation of psbA play an important role in high-light stress responses. A better understanding of the connection between chloroplast gene expression and environmental stress responses is crucial for breeding stress-tolerant crops better able to cope with the rapidly changing environment.
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Jiang, Zhuanzhuan, Li Zhu, Qiuyu Wang, and Xin Hou. "Autophagy-Related 2 Regulates Chlorophyll Degradation under Abiotic Stress Conditions in Arabidopsis." International Journal of Molecular Sciences 21, no. 12 (June 25, 2020): 4515. http://dx.doi.org/10.3390/ijms21124515.
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Chloroplasts are extraordinary organelles for photosynthesis and nutrient storage in plants. During leaf senescence or under stress conditions, damaged chloroplasts are degraded and provide nutrients for developing organs. Autophagy is a high-throughput degradation pathway for intracellular material turnover in eukaryotes. Along with chloroplast degradation, chlorophyll, an important component of the photosynthetic machine, is also degraded. However, the chlorophyll degradation pathways under high light intensity and high temperature stress are not well known. Here, we identified and characterized a novel Arabidopsis mutant, sl2 (seedling lethal 2), showing defective chloroplast development and accelerated chlorophyll degradation. Map-based cloning combined with high-throughput sequencing analysis revealed that a 118.6 kb deletion region was associated with the phenotype of the mutant. Complementary experiments confirmed that the loss of function of ATG2 was responsible for accelerating chlorophyll degradation in sl2 mutants. Furthermore, we analyzed chlorophyll degradation under abiotic stress conditions and found that both chloroplast vesiculation and autophagy take part in chlorophyll degradation under high light intensity and high temperature stress. These results enhanced our understanding of chlorophyll degradation under high light intensity and high temperature stress.
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Bai, Haotian, Haixiang Liu, Xu Chen, Rong Hu, Meng Li, Wei He, Jian Du, et al. "Augmenting photosynthesis through facile AIEgen-chloroplast conjugation and efficient solar energy utilization." Materials Horizons 8, no. 5 (2021): 1433–38. http://dx.doi.org/10.1039/d1mh00012h.
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Two new AIE molecules with activated alkyne groups were successfully conjugated with live chloroplasts by a facile metal-free “Click” reaction, and the formed artificial AIEgen-chloroplast owned the increased photosynthetic activity.
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Peter, Stefan, Otto Spang, Péter Medgyesy, and Christian Schäfer. "Consequences of intergeneric chloroplast transfers on photosynthesis and sensitivity to high light." Functional Plant Biology 26, no. 2 (1999): 171. http://dx.doi.org/10.1071/pp98139.
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Plants with alien chloroplasts (cybrids) were investigated to identify species-specific nucleus-chloroplast interactions which affect the organisation and the functionality of the photosynthetic apparatus. The cybrids had nuclei of Nicotiana tabacum L. and chloroplasts of Atropa belladonna L. (cybrid Nt(Ab)) or Salpiglossis sinuata R. et P. (cybrid Nt(Ss)). Despite the exchange of the chloroplast genome the morphology of the cybrids was similar to their nuclear parent. Also the PSI/PSII ratio was comparable. In Nt(Ab) modified LHCII proteins could be detected which were absent in the parental plants. The trimerisation of LHCII, the chlorophyll contents and the chlorophyll fluorescence parameters were not affected by this modification, but the portion of trimeric LHCII was slightly reduced. In Nt(Ss) the formation of the antenna system was disturbed, and impaired PSII centres could be detected in older leaves. These cybrid-specific features suggest that nucleus-chloroplast interactions are involved in the processing of LHCII and in chloroplast development. High light sensitivity was considerably increased in the cybrids and this risk should be considered when cybridisation is used in crop breeding.
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Hanaoka, Mitsumasa. "New development of plastid signal research." Impact 2020, no. 6 (November 16, 2020): 79–81. http://dx.doi.org/10.21820/23987073.2020.6.79.
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Research into the process of photosynthesis could benefit a range of areas - from increasing output from agriculture and developing stress resistant crops, to the design of solar panels and solar energy harvesting technology. In order to develop our understanding of this process, the study of photosynthesis needs to focus on the chloroplast - the cellular compartments where photosynthesis takes place. Professor Mitsumasa Hanaoka, from the Laboratory of Molecular and Cellular Functions in the Department of Applied Biological Chemistry, Graduate School of Horticulture at Chiba University, is exploring how plants coordinate messages between the nucleus and chloroplasts responsible for optimised photosynthesis.
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Grotjohann, Norbert, David Messdaghi, and Wolfgang Kowallik. "Oxygen Uptake during Photosynthesis of Isolated Pea Chloroplasts." Zeitschrift für Naturforschung C 54, no. 3-4 (April 1, 1999): 209–19. http://dx.doi.org/10.1515/znc-1999-3-411.
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Abstract Mass spectrometric analysis of the gas exchange of illuminated leaflets of 10-14 d old pea seedlings revealed not only 16O2-liberation from photosynthetic H216O-splitting, but also uptake of 18O2, applied to the gas phase of the reaction vessel. Isolated intact chloroplasts of such leaflets suspended in a medium containing NaHCO3 and glycerate 3-phosphate, on irradiation with blue (λ 448 nm) or red (λ 679 nm) light also produced 16O2 from water oxidation and consumed 18O2 from the gas phase. The two reactions were saturated at the same quantum fluence rates. Uptake of 18oxygen was not affected by inhibitors of mitochondrial respiration (alternative pathway included), such as rotenone (5 x l0-5 ᴍ), antimycin A (5 x l0-6 ᴍ), KCN (10-3 ᴍ), SHAM (10-3 ᴍ), or propylgallate (10-3 ᴍ). It was, however, absent, when photosynthetic 16oxygen evolution was completely inhibited by DCMU (10-5 ᴍ). DBMIB (10-5 ᴍ), assumed to prevent electron flow from plastoquinone pool to the cytochrome b6/f-complex, suppressed photosynthetic oxygen evolution, but did not impair uptake of 18O2. A similar result was obtained at application of 4 x l0-5 ᴍ antimycin A. The data are interpreted to show a drain off to molecular oxygen of light-excited electrons from the photosynthetic electron transport chain at the site of plastoquinone pool during photosynthesis. This corresponds to chlororespiration, originally described for Chlamydomonas in darkness by Bennoun (1982). It is discussed, whether O2-uptake during photosynthesis is an additional means for providing ATP for photosynthetic CO2-reduction by increasing the proton gradient across the thylakoid membrane.
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Brunkard, Jacob O., Anne M. Runkel, and Patricia C. Zambryski. "Chloroplasts extend stromules independently and in response to internal redox signals." Proceedings of the National Academy of Sciences 112, no. 32 (July 6, 2015): 10044–49. http://dx.doi.org/10.1073/pnas.1511570112.
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A fundamental mystery of plant cell biology is the occurrence of “stromules,” stroma-filled tubular extensions from plastids (such as chloroplasts) that are universally observed in plants but whose functions are, in effect, completely unknown. One prevalent hypothesis is that stromules exchange signals or metabolites between plastids and other subcellular compartments, and that stromules are induced during stress. Until now, no signaling mechanisms originating within the plastid have been identified that regulate stromule activity, a critical missing link in this hypothesis. Using confocal and superresolution 3D microscopy, we have shown that stromules form in response to light-sensitive redox signals within the chloroplast. Stromule frequency increased during the day or after treatment with chemicals that produce reactive oxygen species specifically in the chloroplast. Silencing expression of the chloroplast NADPH-dependent thioredoxin reductase, a central hub in chloroplast redox signaling pathways, increased chloroplast stromule frequency, whereas silencing expression of nuclear genes related to plastid genome expression and tetrapyrrole biosynthesis had no impact on stromules. Leucoplasts, which are not photosynthetic, also made more stromules in the daytime. Leucoplasts did not respond to the same redox signaling pathway but instead increased stromule formation when exposed to sucrose, a major product of photosynthesis, although sucrose has no impact on chloroplast stromule frequency. Thus, different types of plastids make stromules in response to distinct signals. Finally, isolated chloroplasts could make stromules independently after extraction from the cytoplasm, suggesting that chloroplast-associated factors are sufficient to generate stromules. These discoveries demonstrate that chloroplasts are remarkably autonomous organelles that alter their stromule frequency in reaction to internal signal transduction pathways.
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XiaoYing, Liu, Guo ShiRong, Xu ZhiGang, Jiao XueLei, and Takafumi Tezuka. "Regulation of Chloroplast Ultrastructure, Cross-section Anatomy of Leaves, and Morphology of Stomata of Cherry Tomato by Different Light Irradiations of Light-emitting Diodes." HortScience 46, no. 2 (February 2011): 217–21. http://dx.doi.org/10.21273/hortsci.46.2.217.
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The chloroplast structural alteration and the photosynthetic apparatus activity of cherry tomato seedlings were investigated under dysprosium lamp [white light control (C)] and six light-emitting diode (LED) light treatments designated as red (R), blue (B), orange (O), green (G), red and blue (RB), and red, blue, and green (RBG) with the same photosynthetic photon flux density (PPFD) (≈320 μmol·m−2·s−1) for 30 days. Compared with C treatment, net photosynthesis of cherry tomato leaves was increased significantly under the light treatments of B, RB, and RBG and reduced under R, O, and G. Chloroplasts of the leaves under the RB treatment were rich in grana and starch granules. Moreover, chloroplasts in leaves under RB seemed to be a distinct boundary between granathylakoid and stromathylakoid. Granathylakoid under treatment B developed normally, but the chloroplasts had few starch granules. Chloroplasts under RBG were similar to those under C. Chloroplasts under R and G were relatively rich in starch granules. However, the distinction between granathylakoid and stromathylakoid under R and G was obscure. Chloroplasts under O were dysplastic. Palisade tissue cells in leaves under RB were especially well-developed and spongy tissue cells under the same treatment were localized in an orderly fashion. However, palisade and spongy tissue cells in leaves under R, O, and G were dysplastic. Stomatal numbers per mm2 were significantly increased under B, RB, and RBG. The current results suggested blue light seemed to be an essential factor for the growth of cherry tomato plants.
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Gray, John C., James A. Sullivan, Jun-Hui Wang, Cheryl A. Jerome, and Daniel MacLean. "Coordination of plastid and nuclear gene expression." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 358, no. 1429 (January 29, 2003): 135–45. http://dx.doi.org/10.1098/rstb.2002.1180.
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The coordinated expression of genes distributed between the nuclear and plastid genomes is essential for the assembly of functional chloroplasts. Although the nucleus has a pre–eminent role in controlling chloroplast biogenesis, there is considerable evidence that the expression of nuclear genes encoding photosynthesis–related proteins is regulated by signals from plastids. Perturbation of several plastid–located processes, by inhibitors or in mutants, leads to decreased transcription of a set of nuclear photosynthesis–related genes. Characterization of arabidopsis gun ( genomes uncoupled ) mutants, which express nuclear genes in the presence of norflurazon or lincomycin, has provided evidence for two separate signalling pathways, one involving tetrapyrrole biosynthesis intermediates and the other requiring plastid protein synthesis. In addition, perturbation of photosynthetic electron transfer produces at least two different redox signals, as part of the acclimation to altered light conditions. The recognition of multiple plastid signals requires a reconsideration of the mechanisms of regulation of transcription of nuclear genes encoding photosynthesis–related proteins.
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Giersch, C., and SP Robinson. "Effects of Photoinhibition on Photosynthetic Carbon Metabolism in Intact Isolated Spinach Chloroplasts." Functional Plant Biology 14, no. 4 (1987): 439. http://dx.doi.org/10.1071/pp9870439.
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Pools of intermediates of the Calvin cycle were measured during photosynthetic 14CO2 fixation by intact isolated spinach chloroplasts. Photoinhibitibn (illumination for 8 min with 4000 �mol m-2 s-1 light in the absence of bicarbonate) decreased the subsequently measured rate of CO2 fixation. Individual compounds were differently affected: the ribulose-1,5-bisphosphate (RuBP) pool was drastically lowered, while that of fructose-1,6-bisphosphate (FBP) was increased, suggesting that photoinhibition causes a limitation in RuBP regeneration. An increase in FBP and decrease in RuBP were not observed during photosynthesis in low light at rates of CO2 fixation comparable to those in photoinhibited chloroplasts. This indicates that changes of the metabolite pools induced by photoinhibition were not due solely to decreased rates of electron transport. Activities of RuBP carboxylase and fructose-1,6-bisphosphatase (FBPase) were decreased by the photoinhibitory treatment. However, the activity of both enzymes in photoinhibited chloroplasts was still well in excess of that required to sustain the measured rates of carbon flux. Photoinhibition largely abolished the light-induced proton gradient across the chloroplast envelope. The concomitant acidification of the chloroplast stroma could inhibit FBPase activity. It is concluded that photoinhibition does not result in irreversible modification of the FBPase protein but that its activity may be decreased by changes in pH and possibly other factors in the chloroplast stroma.
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Sato, Naoki. "Complex origins of chloroplast membranes with photosynthetic machineries: multiple transfers of genes from divergent organisms at different times or a single endosymbiotic event?" Journal of Plant Research 133, no. 1 (December 6, 2019): 15–33. http://dx.doi.org/10.1007/s10265-019-01157-z.
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AbstractThe paradigm “cyanobacterial origin of chloroplasts” is currently viewed as an established fact. However, we may have to re-consider the origin of chloroplast membranes, because membranes are not replicated by their own. It is the genes for lipid biosynthetic enzymes that are inherited. In the current understandings, these enzymes became encoded by the nuclear genome as a result of endosymbiotic gene transfer from the endosymbiont. However, we previously showed that many enzymes involved in the synthesis of chloroplast peptidoglycan and glycolipids did not originate from cyanobacteria. Here I present results of comprehensive phylogenetic analysis of chloroplast enzymes involved in fatty acid and lipid biosynthesis, as well as additional chloroplast components related to photosynthesis and gene expression. Four types of phylogenetic relationship between chloroplast enzymes (encoded by the chloroplast and nuclear genomes) and cyanobacterial counterparts were found: type 1, chloroplast enzymes diverged from inside of cyanobacterial clade; type 2, chloroplast and cyanobacterial enzymes are sister groups; type 3, chloroplast enzymes originated from homologs of bacteria other than cyanobacteria; type 4, chloroplast enzymes diverged from eukaryotic homologs. Estimation of evolutionary distances suggested that the acquisition times of chloroplast enzymes were diverse, indicating that multiple gene transfers accounted for the chloroplast enzymes analyzed. Based on the results, I try to relax the tight logic of the endosymbiotic origin of chloroplasts involving a single endosymbiotic event by proposing alternative hypotheses. The hypothesis of host-directed chloroplast formation proposes that glycolipid synthesis ability had been acquired by the eukaryotic host before the acquisition of chloroplast ribosomes. Chloroplast membrane system could have been provided by the host, whereas cyanobacteria contributed to the genes for the genetic and photosynthesis systems, at various times, either before or after the formation of chloroplast membranes. The origin(s) of chloroplasts seems to be more complicated than the single event of primary endosymbiosis.
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Anderson, JM, WS Chow, and DJ Goodchild. "Thylakoid Membrane Organisation in Sun/Shade Acclimation." Functional Plant Biology 15, no. 2 (1988): 11. http://dx.doi.org/10.1071/pp9880011.
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The photosynthetic apparatus of plants responds to changing light quantity and quality with coordinated changes in both the light-harvesting antennae of the photosystems and the amounts of electron transport components and ATP synthase. These compositional modulations are accompanied by changes in thylakoid membrane organisation and photosynthetic capacity. It is now clear that there is a dynamic continuum of organisation and function of the photosynthetic apparatus from the appressed granal and non-appressed stroma thylakoids within a chloroplast, to different chloroplasts within a leaf, to leaves within and between species. While it is very unlikely that there is a unique solution to photosynthesis in the sun or shade, substantial changes in composition, and hence thylakoid membrane organisation and function, are elicited as part of sun/shade responses.
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Han, Shijuan, Stephen C. Maberly, Brigitte Gontero, Zhenfei Xing, Wei Li, Hongsheng Jiang, and Wenmin Huang. "Structural basis for C4 photosynthesis without Kranz anatomy in leaves of the submerged freshwater plant Ottelia alismoides." Annals of Botany 125, no. 6 (January 16, 2020): 869–79. http://dx.doi.org/10.1093/aob/mcaa005.
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Abstract Background and Aims Ottelia alismoides (Hydrocharitaceae) is a freshwater macrophyte that, unusually, possesses three different CO2-concentrating mechanisms. Here we describe its leaf anatomy and chloroplast ultrastructure, how these are altered by CO2 concentration and how they may underlie C4 photosynthesis. Methods Light and transmission electron microscopy were used to study the anatomy of mature leaves of O. alismoides grown at high and low CO2 concentrations. Diel acid change and the activity of phosphoenolpyruvate carboxylase were measured to confirm that CAM activity and C4 photosynthesis were present. Key Results When O. alismoides was grown at low CO2, the leaves performed both C4 and CAM photosynthesis whereas at high CO2 leaves used C4 photosynthesis. The leaf comprised an upper and lower layer of epidermal cells separated by a large air space occupying about 22 % of the leaf transverse-section area, and by mesophyll cells connecting the two epidermal layers. Kranz anatomy was absent. At low CO2, chloroplasts in the mesophyll cells were filled with starch even at the start of the photoperiod, while epidermal chloroplasts contained small starch grains. The number of chloroplasts in the epidermis was greater than in the mesophyll cells. At high CO2, the structure was unchanged but the thicknesses of the two epidermal layers, the air space, mesophyll and the transverse-section area of cells and air space were greater. Conclusions Leaves of O. alismoides have epidermal and mesophyll cells that contain chloroplasts and large air spaces but lack Kranz anatomy. The high starch content of mesophyll cells suggests they may benefit from an internal source of CO2, for example via C4 metabolism, and are also sites of starch storage. The air spaces may help in the recycling of decarboxylated or respired CO2. The structural similarity of leaves at low and high CO2 is consistent with the constitutive nature of bicarbonate and C4 photosynthesis. There is sufficient structural diversity within the leaf of O. alismoides to support dual-cell C4 photosynthesis even though Kranz anatomy is absent.
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Xiong, Liangrong, Hui Du, Keyan Zhang, Duo Lv, Huanle He, Junsong Pan, Run Cai, and Gang Wang. "A Mutation in CsYL2.1 Encoding a Plastid Isoform of Triose Phosphate Isomerase Leads to Yellow Leaf 2.1 (yl2.1) in Cucumber (Cucumis Sativus L.)." International Journal of Molecular Sciences 22, no. 1 (December 30, 2020): 322. http://dx.doi.org/10.3390/ijms22010322.
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The leaf is an important photosynthetic organ and plays an essential role in the growth and development of plants. Leaf color mutants are ideal materials for studying chlorophyll metabolism, chloroplast development, and photosynthesis. In this study, we identified an EMS-induced mutant, yl2.1, which exhibited yellow cotyledons and true leaves that did not turn green with leaf growth. The yl2.1 locus was controlled by a recessive nuclear gene. The CsYL2.1 was mapped to a 166.7-kb genomic region on chromosome 2, which contains 24 predicted genes. Only one non-synonymous single nucleotide polymorphism (SNP) was found between yl2.1 and wt-WD1 that was located in Exon 7 of Csa2G263900, resulting in an amino acid substitution. CsYL2.1 encodes a plastid isoform of triose phosphate isomerase (pdTPI), which catalyzes the reversible conversion of dihydroxyacetone phosphate (DHAP) to glyceraldehyde-3-phosphate (GAP) in chloroplasts. CsYL2.1 was highly expressed in the cotyledons and leaves. The mesophyll cells of the yl2.1 leaves contained reduced chlorophyll and abnormal chloroplasts. Correspondingly, the photosynthetic efficiency of the yl2.1 leaves was impaired. Identification of CsYL2.1 is helpful in elucidating the function of ptTPI in the chlorophyll metabolism and chloroplast development and understanding the molecular mechanism of this leaf color variant in cucumber.
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Heinhorst, S., and G. C. Cannon. "DNA replication in chloroplasts." Journal of Cell Science 104, no. 1 (January 1, 1993): 1–9. http://dx.doi.org/10.1242/jcs.104.1.1.
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Chloroplasts contain multiple copies of a DNA molecule (the plastome) that encodes many of the gene products required to perform photosynthesis. The plastome is replicated by nuclear-encoded proteins and its copy number seems to be highly regulated by the cell in a tissue-specific and developmental manner. Our understanding of the biochemical mechanism by which the plastome is replicated and the molecular basis for its regulation is limited. In this commentary we review our present understanding of chloroplast DNA replication and examine current efforts to elucidate its mechanism at a molecular level.
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Sharon, Yoni, Gal Dishon, and Sven Beer. "The Effects of UV Radiation on Chloroplast Clumping and Photosynthesis in the SeagrassHalophila stipulaceaGrown under High-PAR Conditions." Journal of Marine Biology 2011 (2011): 1–6. http://dx.doi.org/10.1155/2011/483428.
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Since potentially harmful ultraviolet radiation (UVR, 280–400 nm) and high photosynthetically active radiation (PAR, 400–700 nm) are present in the shallow waters of the Gulf of Aqaba where part of the seagrassHalophila stipulacea'spopulation thrives, we examined the effects of high PAR with and without UVR on its photosynthesis and midday chloroplast “clumping phenomenon” (Sharon and Beer 2008). It was found that midday clumping occurred only under high PAR in the presence of UVR, which resulted in a 44% reduction in the absorption cross section (or absorption factor, AF) of the leaves and, accordingly, a parallel lowering of midday electron transport rates (ETR). In addition, UVR had a direct effect on the photosynthetic apparatus by lowering quantum yields and, thus, ETRs, while pigment relations remained unaltered. We conclude that the potentially harmful effects of UVR and high PAR on the photosynthetic apparatus ofHalophila stipulaceaare mitigated by their activation of chloroplast clumping, which functions as a means of protecting most chloroplasts from high irradiances, including UVR.
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Ye, Jie, Weifang Chen, Longwei Feng, Genzhong Liu, Ying Wang, Hanxia Li, Zhibiao Ye, and Yuyang Zhang. "The chaperonin 60 protein SlCpn60α1 modulates photosynthesis and photorespiration in tomato." Journal of Experimental Botany 71, no. 22 (September 11, 2020): 7224–40. http://dx.doi.org/10.1093/jxb/eraa418.
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Abstract Photosynthesis, an indispensable biological process of plants, produces organic substances for plant growth, during which photorespiration occurs to oxidize carbohydrates to achieve homeostasis. Although the molecular mechanism underlying photosynthesis and photorespiration has been widely explored, the crosstalk between the two processes remains largely unknown. In this study, we isolated and characterized a T-DNA insertion mutant of tomato (Solanum lycopersicum) named yellow leaf (yl) with yellowish leaves, retarded growth, and chloroplast collapse that hampered both photosynthesis and photorespiration. Genetic and expression analyses demonstrated that the phenotype of yl was caused by a loss-of-function mutation resulting from a single-copy T-DNA insertion in chaperonin 60α1 (SlCPN60α1). SlCPN60α1 showed high expression levels in leaves and was located in both chloroplasts and mitochondria. Silencing of SlCPN60α1using virus-induced gene silencing and RNA interference mimicked the phenotype of yl. Results of two-dimensional electrophoresis and yeast two-hybrid assays suggest that SlCPN60α1 potentially interacts with proteins that are involved in chlorophyll synthesis, photosynthetic electron transport, and the Calvin cycle, and further affect photosynthesis. Moreover, SlCPN60α1 directly interacted with serine hydroxymethyltransferase (SlSHMT1) in mitochondria, thereby regulating photorespiration in tomato. This study outlines the importance of SlCPN60α1 for both photosynthesis and photorespiration, and provides molecular insights towards plant genetic improvement.
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Bilyavska, Ninel Olexandrivna, Olga Myronivna Fediuk, and Elena Konstantinovna Zolotareva. "Chloroplasts of cold-tolerant plants." Plant Science Today 6, no. 4 (October 1, 2019): 407–11. http://dx.doi.org/10.14719/pst.2019.6.4.584.
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Cold is one of the main stress factors affecting plant growth and development. The structure and function of chloroplasts is most vulnerable to cold. This brief review summarizes the influence of low temperature on both chloroplasts’ structure and functioning across cold-tolerant plant species. One of the features of the chloroplast structure is the presence of stromules. We attempted to define a core set of such changes for plants with different habitats. Some changes might be consistent across all species, which were studied; however, some other characteristics were species- or family-specific. Elucidating the interrelation between the mechanisms controlling photosynthesis during cold stress will facilitate the development of strategies to enhance plant tolerance to low-temperature environmental conditions.
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Boyd, Christine N., Vincent R. Franceschi, Simon D. X. Chuong, Hossein Akhani, Olavi Kiirats, Monica Smith, and Gerald E. Edwards. "Flowers of Bienertia cycloptera and Suaeda aralocaspica (Chenopodiaceae) complete the life cycle performing single-cell C4 photosynthesis." Functional Plant Biology 34, no. 4 (2007): 268. http://dx.doi.org/10.1071/fp06283.
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Leaves and cotyledons of the terrestrial C4 plants, Bienertia cycloptera Bunge ex Boiss. and Suaeda aralocaspica (Bunge) Freitag & Schütze (Chenopodiaceae), accomplish C4 photosynthesis within individual chlorenchyma cells: each species having a unique means of intracellular spatial partitioning of biochemistry and organelles. In this study the chlorenchyma tissue in flowers and stems of these species was investigated. Flowers have an outer whorl of green tepals with a layer of chlorenchyma cells, which are located on the abaxial side, exposed to the atmosphere. Anatomical, immunocytochemical, western blots and starch analyses show that the chlorenchyma cells in tepals are specialised for performance of single-cell C4 photosynthesis like that in leaves. In the tepals of B. cycloptera, chlorenchyma cells have a distinctive central cytoplasmic compartment, with chloroplasts which contain Rubisco, separated by cytoplasmic channels from a peripheral chloroplast-containing compartment, with phosphoenolpyruvate carboxylase (PEPC) distributed throughout the cytoplasm. In the tepals of S. aralocaspica, chlorenchyma cells have chloroplasts polarised towards opposite ends of the cells. Rubisco is found in chloroplasts towards the proximal end of the cell and PEPC is found throughout the cytoplasm. Also, green stems of B. cycloptera have a single layer of the specialised C4 type chlorenchyma cells beneath the epidermis, and in stems of S. aralocaspica, chlorenchyma cells are scattered throughout the cortical tissue with chloroplasts around their periphery, typical of C3 type chlorenchyma. During reproductive development, green flowers become very conspicuous, and their photosynthesis is suggested to be important in completion of the life cycle of these single-cell C4 functioning species.
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Nozoe, Mikio, Yuichi Tsunoyama, Yoko Ishizaki, Yoichi Nakahira, and Takashi Shiina. "Selective Activation of Chloroplast psbD Light-Responsive Promoter and psaA/B Promoter in Transplastomic Tobacco Plants Overexpressing Arabidopsis Sigma Factor AtSIG5." Protein & Peptide Letters 27, no. 2 (January 6, 2020): 168–75. http://dx.doi.org/10.2174/0929866526666191014130605.
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Background: Plastid-encoded eubacterial-type RNA polymerase (PEP) plays a critical role in the transcription of photosynthesis genes in chloroplasts. Notably, some of the reaction center genes, including psaA, psaB, psbA, and psbD genes, are differentially transcribed by PEP in mature chloroplasts. However, the molecular mechanism of promoter selection in the reaction center gene transcription by PEP is not well understood. Objective: Sigma factor proteins direct promoter selection by a core PEP in chloroplasts as well as bacteria. AtSIG5 is a unique chloroplast sigma factor essential for psbD light-responsive promoter (psbD LRP) activity. To analyze the role of AtSIG5 in chloroplast transcription in more detail, we assessed the effect of AtSIG5 hyper-expression on the transcription of plastid-encoded genes in chloroplast transgenic plants. Results: The chloroplast transgenic tobacco (CpOX-AtSIG5) accumulates AtSIG5 protein at extremely high levels in chloroplasts. Due to the extremely high-level expression of recombinant AtSIG5, most PEP holoenzymes are most likely to include the recombinant AtSIG5 in the CpOXAtSIG5 chloroplasts. Thus, we can assess the promoter preference of AtSIG5 in vivo. The overexpression of AtSIG5 significantly increased the expression of psbD LRP transcripts encoding PSII reaction center D2 protein and psaA/B operon transcripts encoding PSI core proteins. Furthermore, run-on transcription analyses revealed that AtSIG5 preferentially recognizes the psaA/B promoter, as well as the psbD LRP. Moreover, we found that psbD LRP is constitutively active in CpOX-AtSIG5 plants irrespective of light and dark. Conclusion: AtSIG5 probably plays a significant role in differential transcription of reaction center genes in mature chloroplasts.
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Dolinsky, Margaret, and Roger P. Hangarter. "The Living Canvas: Interactive Chloroplasts." Leonardo 50, no. 2 (April 2017): 207–8. http://dx.doi.org/10.1162/leon_a_01231.
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The Living Canvas is a science/art/educational exhibit of artwork created by using the positioning of chloroplasts in leaf cells as an artistic medium and using light to control that medium. The work reveals the process of chloroplast movements as they occur in leaf cells and how those subcellular changes affect the optical properties of whole leaves to maximize photosynthesis. The works are designed to stimulate a sense of intrigue and awe to enhance the viewers’ awareness of plant life and their relationships with plants in their environment.
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Robinson, SP, and C. Giersch. "Inorganic Phosphate Concentration in the Stroma of Isolated Chloroplasts and Its Influence on Photosynthesis." Functional Plant Biology 14, no. 4 (1987): 451. http://dx.doi.org/10.1071/pp9870451.
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The concentration of inorganic orthophosphate (Pi) was determined in the stroma of isolated chloroplasts during photosynthesis under Pi-saturated and Pi-limited conditions. Pi was determined calorimetrically or by high performance liquid chromatography of extracts of chloroplasts labelled with 32Pi. When chloroplasts were illuminated in the absence of added Pi, photosynthesis soon declined due to Pi-depletion. After 5 min in the light, photosynthesis had declined to 2% of the maximum rate. At this point, stromal Pi was estimated to be 1.4 mM by the colorimetric method and 0.2 mM by 32P chromatography. Using the colorimetric method, Pi equivalent to approximately 1 mM in the stroma was found to be associated with thylakoid membranes isolated from chloroplasts, irrespective of the Pi content of the intact chloroplasts. This was considered to be a non-metabolic pool of Pi. During steady- state photosynthesis with optimal concentrations of Pi added to the reaction medium, the stromal Pi concentration was estimated to be 2.6 mM and 1.6 mM with the colorimetric and 32P methods, respectively. Measurement of stromal 32Pi in chloroplasts illuminated with varying concentrations of 32Pi in the reaction medium suggested that photosynthesis was saturated at stromal Pi concentrations above 2.0-2.5 mM. Photophosphorylation by thylakoid membranes was saturated at Pi concentrations above 1.2-1.5 mM. It is concluded that, during photosynthesis in isolated chloroplasts in the presence of an optimal supply of Pi from the reaction medium, the stromal Pi concentration is just above that required to saturate photophosphorylation. Any decrease in the supply of Pi from the medium results in a rapid decrease in stromal Pi to the point where photophosphorylation may become Pi-limited, decreasing the rate of CO2 fixation.
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Sato, Naoki. "Are Cyanobacteria an Ancestor of Chloroplasts or Just One of the Gene Donors for Plants and Algae?" Genes 12, no. 6 (May 27, 2021): 823. http://dx.doi.org/10.3390/genes12060823.
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Chloroplasts of plants and algae are currently believed to originate from a cyanobacterial endosymbiont, mainly based on the shared proteins involved in the oxygenic photosynthesis and gene expression system. The phylogenetic relationship between the chloroplast and cyanobacterial genomes was important evidence for the notion that chloroplasts originated from cyanobacterial endosymbiosis. However, studies in the post-genomic era revealed that various substances (glycolipids, peptidoglycan, etc.) shared by cyanobacteria and chloroplasts are synthesized by different pathways or phylogenetically unrelated enzymes. Membranes and genomes are essential components of a cell (or an organelle), but the origins of these turned out to be different. Besides, phylogenetic trees of chloroplast-encoded genes suggest an alternative possibility that chloroplast genes could be acquired from at least three different lineages of cyanobacteria. We have to seriously examine that the chloroplast genome might be chimeric due to various independent gene flows from cyanobacteria. Chloroplast formation could be more complex than a single event of cyanobacterial endosymbiosis. I present the “host-directed chloroplast formation” hypothesis, in which the eukaryotic host cell that had acquired glycolipid synthesis genes as an adaptation to phosphate limitation facilitated chloroplast formation by providing glycolipid-based membranes (pre-adaptation). The origins of the membranes and the genome could be different, and the origin of the genome could be complex.
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Ghoshroy, Soumitra, and Wayne R. Fagerberg. "Light-detection system in higher-plant chloroplasts : Pigment mediated or energy related." Proceedings, annual meeting, Electron Microscopy Society of America 50, no. 2 (August 1992): 1668–69. http://dx.doi.org/10.1017/s0424820100132972.
Full textAbstract:
Light is the driving force of photosynthesis. Plants adapt to rapid changes in irradiance, quality and duration of the light environment by modulating the composition of the thylakoid membranes to make the best use of the available light energy. Each chloroplast contains a large amount of thylakoid membranes some of which may be arranged as stacks (granal thylakoids) and others as unstacked sacks (stromal thylakoids). Shaded chloroplasts develop more thylakoid surface area as compared to those growing in full sunlight. Conversion of sun-type chloroplasts to those of shade-types can occur quickly, when sun plants are shaded. However, the response mechanism of chloroplasts to changes in light levels is yet to be understood. Reports in the literature showed that plants grown in red light developed more grana compared to those grown under blue light and a pigment detection system has been postulated. While, other models propose that overall energy flux changes within the chloroplast induce sun/shade response.
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Allen, John F., and Thomas Pfannschmidt. "Balancing the two photosystems: photosynthetic electron transfer governs transcription of reaction centre genes in chloroplasts." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 355, no. 1402 (October 29, 2000): 1351–59. http://dx.doi.org/10.1098/rstb.2000.0697.
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Chloroplasts are cytoplasmic organelles whose primary function is photosynthesis, but which also contain small, specialized and quasi–autonomous genetic systems. In photosynthesis, two energy converting photosystems are connected, electrochemically, in series. The connecting electron carriers are oxidized by photosystem I (PS I) and reduced by photosystem II (PS II). It has recently been shown that the oxidation–reduction state of one connecting electron carrier, plastoquinone, controls transcription of chloroplast genes for reaction centre proteins of the two photosystems. The control counteracts the imbalance in electron transport that causes it: oxidized plastoquinone induces PS II and represses PS I; reduced plastoquinone induces PS I and represses PS II. This complementarity is observed both in vivo , using light favouring one or other photosystem, and in vitro , when site–specific electron transport inhibitors are added to transcriptionally and photosynthetically active chloroplasts. There is thus a transcriptional level of control that has a regulatory function similar to that of purely post–translational ‘state transitions’ in which the redistribution of absorbed excitation energy between photosystems is mediated by thylakoid membrane protein phosphorylation. The changes in rates of transcription that are induced by spectral changes in vivo can be detected even before the corresponding state transitions are complete, suggesting the operation of a branched pathway of redox signal transduction. These findings suggest a mechanism for adjustment of photosystem stoichiometry in which initial events involve a sensor of the redox state of plastoquinone, and may thus be the same as the initial events of state transitions. Redox control of chloroplast transcription is also consistent with the proposal that a direct regulatory coupling between electron transport and gene expression determines the function and composition of the chloroplast's extra–nuclear genetic system.
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Neill, Samuel O., and Kevin S. Gould. "Anthocyanins in leaves: light attenuators or antioxidants?" Functional Plant Biology 30, no. 8 (2003): 865. http://dx.doi.org/10.1071/fp03118.
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Anthocyanins have the potential to mitigate photooxidative injury in leaves, both by shielding chloroplasts from excess high-energy quanta, and by scavenging reactive oxygen species. To distinguish between the impacts of these two putative mechanisms, superoxide (O2•–) concentration and chlorophyll oxidation were measured for Lactuca sativa L. chloroplast suspensions under various light and antioxidant-supplemented environments. A red cellulose filter, the optical properties of which approximated that of anthocyanin, effected a 33% decline in rate of O2•– generation and 37% reduction in chlorophyll bleaching, when used to shield irradiated chloroplasts. Colourless and blue tautomers of cyanidin 3-(6-malonyl)glucoside at pH 7 removed up to 17% of O2•– generated by chloroplasts, indicating that cytosolic anthocyanins can serve as effective antioxidants. Red tautomers, typical of vacuolar anthocyanins, also showed strong reducing potentials as indicated by cyclic voltammetry. These potentials declined by 40% after 15 min exposure to O2•–. Maximum quantum efficiencies of photosynthesis were similar for red and green portions of intact L. sativa leaves, but the red regions were less photoinhibited, and recovered more extensively after exposures to strong light. Anthocyanins evidently offer effective and versatile protection to leaves without significantly compromising photosynthesis.
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Gao, Tong-Mei, Shuang-Ling Wei, Jing Chen, Yin Wu, Feng Li, Li-Bin Wei, Chun Li, et al. "Cytological, genetic, and proteomic analysis of a sesame (Sesamum indicum L.) mutant Siyl-1 with yellow–green leaf color." Genes & Genomics 42, no. 1 (November 1, 2019): 25–39. http://dx.doi.org/10.1007/s13258-019-00876-w.
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Abstract Background Both photosynthetic pigments and chloroplasts in plant leaf cells play an important role in deciding on the photosynthetic capacity and efficiency in plants. Systematical investigating the regulatory mechanism of chloroplast development and chlorophyll (Chl) content variation is necessary for clarifying the photosynthesis mechanism for crops. Objective This study aims to explore the critical regulatory mechanism of leaf color mutation in a yellow–green leaf sesame mutant Siyl-1. Methods We performed the genetic analysis of the yellow-green leaf color mutation using the F2 population of the mutant Siyl-1. We compared the morphological structure of the chloroplasts, chlorophyll content of the three genotypes of the mutant F2 progeny. We performed the two-dimensional gel electrophoresis (2-DE) and compared the protein expression variation between the mutant progeny and the wild type. Results Genetic analysis indicated that there were 3 phenotypes of the F2 population of the mutant Siyl-1, i.e., YY type with light-yellow leaf color (lethal); Yy type with yellow-green leaf color, and yy type with normal green leaf color. The yellow-green mutation was controlled by an incompletely dominant nuclear gene, Siyl-1. Compared with the wild genotype, the chloroplast number and the morphological structure in YY and Yy mutant lines varied evidently. The chlorophyll content also significantly decreased (P < 0.05). The 2-DE comparison showed that there were 98 differentially expressed proteins (DEPs) among YY, Yy, and yy lines. All the 98 DEPs were classified into 5 functional groups. Of which 82.7% DEPs proteins belonged to the photosynthesis and energy metabolism group. Conclusion The results revealed the genetic character of yellow-green leaf color mutant Siyl-1. 98 DEPs were found in YY and Yy mutant compared with the wild genotype. The regulation pathway related with the yellow leaf trait mutation in sesame was analyzed for the first time. The findings supplied the basic theoretical and gene basis for leaf color and chloroplast development mechanism in sesame.
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Yokochi, Yuichi, Keisuke Yoshida, Florian Hahn, Atsuko Miyagi, Ken-ichi Wakabayashi, Maki Kawai-Yamada, Andreas P. M. Weber, and Toru Hisabori. "Redox regulation of NADP-malate dehydrogenase is vital for land plants under fluctuating light environment." Proceedings of the National Academy of Sciences 118, no. 6 (February 2, 2021): e2016903118. http://dx.doi.org/10.1073/pnas.2016903118.
Full textAbstract:
Many enzymes involved in photosynthesis possess highly conserved cysteine residues that serve as redox switches in chloroplasts. These redox switches function to activate or deactivate enzymes during light-dark transitions and have the function of fine-tuning their activities according to the intensity of light. Accordingly, many studies on chloroplast redox regulation have been conducted under the hypothesis that “fine regulation of the activities of these enzymes is crucial for efficient photosynthesis.” However, the impact of the regulatory system on plant metabolism is still unclear. To test this hypothesis, we here studied the impact of the ablation of a redox switch in chloroplast NADP-malate dehydrogenase (MDH). By genome editing, we generated a mutant plant whose MDH lacks one of its redox switches and is active even in dark conditions. Although NADPH consumption by MDH in the dark is expected to be harmful to plant growth, the mutant line did not show any phenotypic differences under standard long-day conditions. In contrast, the mutant line showed severe growth retardation under short-day or fluctuating light conditions. These results indicate that thiol-switch redox regulation of MDH activity is crucial for maintaining NADPH homeostasis in chloroplasts under these conditions.
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Jin, Yongsheng, Dongyuan Ma, Jiangli Dong, Daofeng Li, Changwang Deng, Jingchen Jin, and Tao Wang. "The HC-Pro Protein of Potato Virus Y Interacts with NtMinD of Tobacco." Molecular Plant-Microbe Interactions® 20, no. 12 (December 2007): 1505–11. http://dx.doi.org/10.1094/mpmi-20-12-1505.
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Potato virus Y (PVY) infections often lead to altered numbers of host plant chloroplasts, as well as changes in morphology and inhibited photosynthesis. The multifunctional protein helper component-proteinase, HC-Pro, has been identified in PVY-infected leaf chloroplasts. We used yeast two-hybrid and bimolecular fluorescence complementation assays to demonstrate that HC-Pro can interact with the chloroplast division-related factor NtMinD in yeast and tobacco cells, respectively. In addition, we confirmed that residues 271 to 314 in NtMinD are necessary for its interaction with PVY HC-Pro in a yeast two-hybrid analysis using four NtMinD deletion mutants. These residues are necessary for the dimerization of NtMinD, which plays a vital role in chloroplast division. Thus, PVY HC-Pro may affect NtMinD activity by inhibiting the formation of NtMinD homodimers, and this may interfere with chloroplast division and contribute to changes in the numbers of chloroplast per cell observed in PVY-infected plants.
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Alomrani, Sarah, Karl J. Kunert, and Christine H. Foyer. "Papain-like cysteine proteases are required for the regulation of photosynthetic gene expression and acclimation to high light stress." Journal of Experimental Botany 72, no. 9 (March 4, 2021): 3441–54. http://dx.doi.org/10.1093/jxb/erab101.
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AbstractChloroplasts are considered to be devoid of cysteine proteases. Using transgenic Arabidopsis lines expressing the rice cystatin, oryzacystatin I (OC-I), in the chloroplasts (PC lines) or cytosol (CYS lines), we explored the hypothesis that cysteine proteases regulate photosynthesis. The CYS and PC lines flowered later than the wild type (WT) and accumulated more biomass after flowering. In contrast to the PC rosettes, which accumulated more leaf chlorophyll and carotenoid pigments than the WT, the CYS lines had lower amounts of leaf pigments. High-light-dependent decreases in photosynthetic carbon assimilation and the abundance of the Rubisco large subunit protein, the D1 protein, and the phosphorylated form of D1 proteins were attenuated in the CYS lines and reversed in the PC lines relative to the WT. However, the transgenic lines had higher amounts of LHC, rbcs, pasbA, and pasbD transcripts than the WT, and also showed modified chloroplast to nucleus signalling. We conclude that cysteine proteases accelerate the reconfiguration of the chloroplast proteome after flowering and in response to high-light stress. Inhibition of cysteine proteases, such as AtCEP1, slows chloroplast protein degradation and stimulates photosynthetic gene expression and chloroplast to nucleus signalling, enhancing stress tolerance traits.
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Krause, G. Heinrich, and Henrik Laasch. "Energy-Dependent Chlorophyll Fluorescence Quenching in Chloroplasts Correlated with Quantum Yield of Photosynthesis." Zeitschrift für Naturforschung C 42, no. 5 (May 1, 1987): 581–84. http://dx.doi.org/10.1515/znc-1987-0514.
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Abstract Chlorophyll a fluorescence quenching was studied in intact, CO2 fixing chloroplasts isolated from spinach. Energy-dependent quenching (qᴇ), which is correlated with the light-induced pro ton gradient across the thylakoid membrane presumably reflects an increase in the rate-constant of thermal dissipation of excitation energy in the photosynthetic pigment system . The extent of qᴇ was found to be linearly related to the decrease of quantum yield of photosynthesis. We suggest that this relationship indicates a dynamic property of the membrane to adjust thermal dissipation of absorbed light energy to the energy requirement of photosynthesis.
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Forsberg, J., M. Rosenquist, L. Fraysse, and J. F. Allen. "Redox signalling in chloroplasts and mitochondria: genomic and biochemical evidence for two-component regulatory systems in bioenergetic organelles." Biochemical Society Transactions 29, no. 4 (August 1, 2001): 403–7. http://dx.doi.org/10.1042/bst0290403.
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Redox chemistry is central to the primary functions of chloroplasts and mitochondria, that is, to energy conversion in photosynthesis and respiration. However, these bioenergetic organelles always contain very small, specialized genetic systems, relics of their bacterial origin. At huge cost, organellar genomes contain, typically, a mere 0.1 % of the genetic information in a eukaryotic cell. There is evidence that chloroplast and mitochondrial genomes encode proteins whose function and biogenesis are particularly tightly governed by electron transfer. We have identified nuclear genes for ‘bacterial’ histidine sensor kinases and aspartate response regulators that seem to be targeted to chloroplast and mitochondrial membranes. Sequence similarities to cyano-bacterial redox signalling components indicate homology and suggest conserved sensory and signalling functions. Two-component redox signalling pathways might be ancient, conserved mechanisms that permit endogenous control over the biogenesis, in situ, of bioenergetic complexes of chloroplasts and mitochondria.
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Krupa, Zbigniew. "Cadmium against Higher Plant Photosynthesis -a Variety of Effects and Where Do They Possibly Come From?" Zeitschrift für Naturforschung C 54, no. 9-10 (October 1, 1999): 723–29. http://dx.doi.org/10.1515/znc-1999-9-1017.
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The complexity of in vivo toxic effects of Cd on higher plants makes almost impossible an accurate distinction between direct and indirect mechanisms of its action on the photosynthetic apparatus. We, therefore, postulate that multiple Cd effects on plant physiological and metabolic processes may finally be focused on photosynthesis. This would also explain the phenomenon that only a small fraction of Cd entering chloroplasts may cause such disastrous changes in their structure and function. In return, the inhibition of photosynthesis affects numerous metabolic pathways dependent on the primary carbon metabolism
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Liu, Miao, Xiucheng Liu, Xuhua Du, Helena Korpelainen, Ülo Niinemets, and Chunyang Li. "Anatomical variation of mesophyll conductance due to salt stress in Populus cathayana females and males growing under different inorganic nitrogen sources." Tree Physiology 41, no. 8 (February 8, 2021): 1462–78. http://dx.doi.org/10.1093/treephys/tpab017.
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Abstract Synergistic regulation in leaf architecture and photosynthesis is essential for salt tolerance. However, how plant sex and inorganic nitrogen sources alter salt stress-dependent photosynthesis remains unknown. Leaf anatomical characteristics and photosynthesis of Populus cathayana Rehder females and males were investigated under salt stress conditions combined with nitrate NO3− and ammonium NH4+ supplies to clarify the underlying mechanisms. In salt-stressed females, we observed an increased mesophyll spongy cell density, a reduced chloroplast density, a decreased surface area of chloroplasts adjacent to the intercellular air space (Sc/S) and an increased mesophyll cell area per transverse section width (S/W), consequently causing mesophyll conductance (gm) and photosynthesis inhibition, especially under NH4+ supply. Conversely, males with a greater mesophyll palisade tissue thickness and chloroplast density, but a lower spongy cell density had lower S/W and higher Sc/S, and higher gm and photosynthesis. NH4+-fed females had a lower CO2 conductance through cell wall and stromal conductance perpendicular to the cell wall, but a higher chloroplast conductance from the cell wall (gcyt1) than females supplied with NO3−, whereas males had a higher chloroplast conductance and lower CO2 conductance through cell wall when supplied with NO3− instead of NH4+ under salt stress. These findings indicate sex-specific strategies in coping with salt stress related to leaf anatomy and gm under both types of nitrogen supplies, which may contribute to sex-specific CO2 capture and niche segregation.
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Springer, Armin, ChulHee Kang, Sachin Rustgi, Diter von Wettstein, Christiane Reinbothe, Stephan Pollmann, and Steffen Reinbothe. "Programmed chloroplast destruction during leaf senescence involves 13-lipoxygenase (13-LOX)." Proceedings of the National Academy of Sciences 113, no. 12 (March 11, 2016): 3383–88. http://dx.doi.org/10.1073/pnas.1525747113.
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Leaf senescence is the terminal stage in the development of perennial plants. Massive physiological changes occur that lead to the shut down of photosynthesis and a cessation of growth. Leaf senescence involves the selective destruction of the chloroplast as the site of photosynthesis. Here, we show that 13-lipoxygenase (13-LOX) accomplishes a key role in the destruction of chloroplasts in senescing plants and propose a critical role of its NH2-terminal chloroplast transit peptide. The 13-LOX enzyme identified here accumulated in the plastid envelope and catalyzed the dioxygenation of unsaturated membrane fatty acids, leading to a selective destruction of the chloroplast and the release of stromal constituents. Because 13-LOX pathway products comprise compounds involved in insect deterrence and pathogen defense (volatile aldehydes and oxylipins), a mechanism of unmolested nitrogen and carbon relocation is suggested that occurs from leaves to seeds and roots during fall.
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Dmitrieva, Valeria A., Valentina V. Domashkina, Alexandra N. Ivanova, Vladimir S. Sukhov, Elena V. Tyutereva, and Olga V. Voitsekhovskaja. "Regulation of plasmodesmata in Arabidopsis leaves: ATP, NADPH and chlorophyll b levels matter." Journal of Experimental Botany 72, no. 15 (May 11, 2021): 5534–52. http://dx.doi.org/10.1093/jxb/erab205.
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Abstract In mature leaves, cell-to-cell transport via plasmodesmata between mesophyll cells links the production of assimilates by photosynthesis with their export to sink organs. This study addresses the question of how signals derived from chloroplasts and photosynthesis influence plasmodesmata permeability. Cell-to-cell transport was analyzed in leaves of the Arabidopsis chlorophyll b-less ch1-3 mutant, the same mutant complemented with a cyanobacterial CAO gene (PhCAO) overaccumulating chlorophyll b, the trxm3 mutant lacking plastidial thioredoxin m3, and the ntrc mutant lacking functional NADPH:thioredoxin reductase C. The regulation of plasmodesmata permeability in these lines could not be traced back to the reduction state of the thioredoxin system or the types and levels of reactive oxygen species produced in chloroplasts; however, it could be related to chloroplast ATP and NADPH production. The results suggest that light enables plasmodesmata closure via an increase in the ATP and NADPH levels produced in photosynthesis, providing a control mechanism for assimilate export based on the rate of photosynthate production in the Calvin–Benson cycle. The level of chlorophyll b influences plasmodesmata permeability via as-yet-unidentified signals. The data also suggest a role of thioredoxin m3 in the regulation of cyclic electron flow around photosystem I.