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1
Zhukova, G. Ya. "Embryogenesis of angiosperms: ultrastructural transformations of plastids." Acta Societatis Botanicorum Poloniae 50, no. 1-2 (2014): 303–6. http://dx.doi.org/10.5586/asbp.1981.049.
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Electron microscopic study of <em>Alcea rosea</em> and <em>Valeriana officinalis</em> embryogenesis showed the ultrastructural changes in the embryo plastidome. It is assumed that plastids of the mature angiosperms zygote are of one genetic type. Tissue ditferentiation and changes of plastid functions in the course of embryogenesis and plant development underlie the histological differentiation of plastids and their ontogenic transformations (metamorphosis).
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Havurinne, Vesa, Maria Handrich, Mikko Antinluoma, Sergey Khorobrykh, Sven B. Gould, and Esa Tyystjärvi. "Genetic autonomy and low singlet oxygen yield support kleptoplast functionality in photosynthetic sea slugs." Journal of Experimental Botany 72, no. 15 (May 15, 2021): 5553–68. http://dx.doi.org/10.1093/jxb/erab216.
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Abstract The kleptoplastic sea slug Elysia chlorotica consumes Vaucheria litorea, stealing its plastids, which then photosynthesize inside the animal cells for months. We investigated the properties of V. litorea plastids to understand how they withstand the rigors of photosynthesis in isolation. Transcription of specific genes in laboratory-isolated V. litorea plastids was monitored for 7 days. The involvement of plastid-encoded FtsH, a key plastid maintenance protease, in recovery from photoinhibition in V. litorea was estimated in cycloheximide-treated cells. In vitro comparison of V. litorea and spinach thylakoids was applied to investigate reactive oxygen species formation in V. litorea. In comparison to other tested genes, the transcripts of ftsH and translation elongation factor EF-Tu (tufA) decreased slowly in isolated V. litorea plastids. Higher levels of FtsH were also evident in cycloheximide-treated cells during recovery from photoinhibition. Charge recombination in PSII of V. litorea was found to be fine-tuned to produce only small quantities of singlet oxygen, and the plastids also contained reactive oxygen species-protective compounds. Our results support the view that the genetic characteristics of the plastids are crucial in creating a photosynthetic sea slug. The plastid’s autonomous repair machinery is likely enhanced by low singlet oxygen production and elevated expression of FtsH.
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Larkin, Robert M. "Influence of plastids on light signalling and development." Philosophical Transactions of the Royal Society B: Biological Sciences 369, no. 1640 (April 19, 2014): 20130232. http://dx.doi.org/10.1098/rstb.2013.0232.
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In addition to their contribution to metabolism, chloroplasts emit signals that influence the expression of nuclear genes that contribute to numerous plastidic and extraplastidic processes. Plastid-to-nucleus signalling optimizes chloroplast function, regulates growth and development, and affects responses to environmental cues. An incomplete list of plastid signals is available and particular plastid-to-nucleus signalling mechanisms are partially understood. The plastid-to-nucleus signalling that depends on the GENOMES UNCOUPLED ( GUN ) genes couples the expression of nuclear genes to the functional state of the chloroplast. Analyses of gun mutants provided insight into the mechanisms and biological functions of plastid-to-nucleus signalling. GUN genes contribute to chloroplast biogenesis, the circadian rhythm, stress tolerance, light signalling and development. Some have criticized the gun mutant screen for employing inhibitors of chloroplast biogenesis and suggested that gun alleles do not disrupt significant plastid-to-nucleus signalling mechanisms. Here, I briefly review GUN -dependent plastid-to-nucleus signalling, explain the flaws in the major criticisms of the gun mutant screen and review the influence of plastids on light signalling and development.
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Kim, Eunsoo, and Shinichiro Maruyama. "A contemplation on the secondary origin of green algal and plant plastids." Acta Societatis Botanicorum Poloniae 83, no. 4 (2014): 331–36. http://dx.doi.org/10.5586/asbp.2014.040.
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A single origin of plastids and the monophyly of three “primary” plastid-containing groups – the Chloroplastida (or Viridiplantae; green algae+land plants), Rhodophyta, and Glaucophyta – are widely accepted, mainstream hypotheses that form the basis for many comparative evolutionary studies. This “Archaeplastida” hypothesis, however, thus far has not been unambiguously confirmed by phylogenetic studies based on nucleocytoplasmic markers. In view of this as well as other lines of evidence, we suggest the testing of an alternate hypothesis that plastids of the Chloroplastida are of secondary origin. The new hypothesis is in agreement with, or perhaps better explains, existing data, including both the plastidal and nucleocytoplasmic characteristics of the Chloroplastida in comparison to those of other groups.
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Reddy, M. K., and N. C. Subrahmanyam. "Nuclear gene induced plastid alterations in Pennisetum americanum." Genome 30, no. 2 (April 1, 1988): 147–51. http://dx.doi.org/10.1139/g88-025.
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A nonlethal stripe mutant (700430) of Pennisetum americanum was crossed reciprocally with other normal inbred lines to establish its inheritance pattern. A recessive nuclear gene, when homozygous, led to defective plastid development with variable penetrance and expressivity. Intraplant and interspikelet crosses revealed maternal plastid transmission. When stripe plants were crossed with pollen from normal inbreds, green and yellow progeny were obtained; selfing stripe plants or crossing with its green sib produced yellow, stripe, and green progeny. These results suggest that in egg cells with exclusively defective plastids, the plastids do not revert back inspite of acquiring a dominant allele from the pollen parent, while in egg cells with a mixture of green and yellow plastids, the yellow plastids could develop into functional plastids under the influence of a dominant allele.Key words: altered plastids, variable penetrance, plastid transmission, plastid reversion.
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Dorrell, Richard G., and Christopher J. Howe. "Integration of plastids with their hosts: Lessons learned from dinoflagellates." Proceedings of the National Academy of Sciences 112, no. 33 (May 20, 2015): 10247–54. http://dx.doi.org/10.1073/pnas.1421380112.
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After their endosymbiotic acquisition, plastids become intimately connected with the biology of their host. For example, genes essential for plastid function may be relocated from the genomes of plastids to the host nucleus, and pathways may evolve within the host to support the plastid. In this review, we consider the different degrees of integration observed in dinoflagellates and their associated plastids, which have been acquired through multiple different endosymbiotic events. Most dinoflagellate species possess plastids that contain the pigment peridinin and show extreme reduction and integration with the host biology. In some species, these plastids have been replaced through serial endosymbiosis with plastids derived from a different phylogenetic derivation, of which some have become intimately connected with the biology of the host whereas others have not. We discuss in particular the evolution of the fucoxanthin-containing dinoflagellates, which have adapted pathways retained from the ancestral peridinin plastid symbiosis for transcript processing in their current, serially acquired plastids. Finally, we consider why such a diversity of different degrees of integration between host and plastid is observed in different dinoflagellates and how dinoflagellates may thus inform our broader understanding of plastid evolution and function.
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Kohler, R. H., and M. R. Hanson. "Plastid tubules of higher plants are tissue-specific and developmentally regulated." Journal of Cell Science 113, no. 1 (January 1, 2000): 81–89. http://dx.doi.org/10.1242/jcs.113.1.81.
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Green fluorescent stroma filled tubules (stromules) emanating from the plastid surface were observed in transgenic plants containing plastid-localized green fluorescent protein (GFP). These transgenic tobacco plants were further investigated by epifluorescence and confocal laser scanning microscopy (CSLM) to identify developmental and/or cell type specific differences in the abundance and appearance of stromules and of plastids. Stromules are rarely seen on chlorophyll-containing plastids in cell types such as trichomes, guard cells or mesophyll cells of leaves. In contrast, they are abundant in tissues that contain chlorophyll-free plastids, such as petal and root. The morphology of plastids in roots and petals is highly dynamic, and plastids are often elongated and irregular. The shapes, size, and position of plastids vary in particular developmental zones of the root. Furthermore, suspension cells of tobacco exhibit stromules on virtually every plastid with two major forms of appearance. The majority of cells show a novel striking ‘octopus- or millipede-like’ structure with plastid bodies clustered around the nucleus and with long thin stromules of up to at least 40 (micro)m length stretching into distant areas of the cell. The remaining cells have plastid bodies distributed throughout the cell with short stromules. Photobleaching experiments indicated that GFP can flow through stromules and that the technique can be used to distinguish interconnected plastids from independent plastids.
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de Koning, Audrey P., and Patrick J. Keeling. "Nucleus-Encoded Genes for Plastid-Targeted Proteins in Helicosporidium: Functional Diversity of a Cryptic Plastid in a Parasitic Alga." Eukaryotic Cell 3, no. 5 (October 2004): 1198–205. http://dx.doi.org/10.1128/ec.3.5.1198-1205.2004.
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ABSTRACT Plastids are the organelles of plants and algae that house photosynthesis and many other biochemical pathways. Plastids contain a small genome, but most of their proteins are encoded in the nucleus and posttranslationally targeted to the organelle. When plants and algae lose photosynthesis, they virtually always retain a highly reduced “cryptic” plastid. Cryptic plastids are known to exist in many organisms, although their metabolic functions are seldom understood. The best-studied example of a cryptic plastid is from the intracellular malaria parasite, Plasmodium, which has retained a plastid for the biosynthesis of fatty acids, isoprenoids, and heme by the use of plastid-targeted enzymes. To study a completely independent transformation of a photosynthetic plastid to a cryptic plastid in another alga-turned-parasite, we conducted an expressed sequence tag (EST) survey of Helicosporidium. This parasite has recently been recognized as a highly derived green alga. Based on phylogenetic relationships to other plastid homologues and the presence of N-terminal transit peptides, we have identified 20 putatively plastid-targeted enzymes that are involved in a wide variety of metabolic pathways. Overall, the metabolic diversity of the Helicosporidium cryptic plastid exceeds that of the Plasmodium plastid, as it includes representatives of most of the pathways known to operate in the Plasmodium plastid as well as many others. In particular, several amino acid biosynthetic pathways have been retained, including the leucine biosynthesis pathway, which was only recently recognized in plant plastids. These two parasites represent different evolutionary trajectories in plastid metabolic adaptation.
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Hirakawa, Yoshihisa, Fabien Burki, and Patrick J. Keeling. "Genome-Based Reconstruction of the Protein Import Machinery in the Secondary Plastid of a Chlorarachniophyte Alga." Eukaryotic Cell 11, no. 3 (January 20, 2012): 324–33. http://dx.doi.org/10.1128/ec.05264-11.
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ABSTRACT Most plastid proteins are encoded by their nuclear genomes and need to be targeted across multiple envelope membranes. In vascular plants, the translocons at the outer and inner envelope membranes of chloroplasts (TOC and TIC, respectively) facilitate transport across the two plastid membranes. In contrast, several algal groups harbor more complex plastids, the so-called secondary plastids, which are surrounded by three or four membranes, but the plastid protein import machinery (in particular, how proteins cross the membrane corresponding to the secondary endosymbiont plasma membrane) remains unexplored in many of these algae. To reconstruct the putative protein import machinery of a secondary plastid, we used the chlorarachniophyte alga Bigelowiella natans , whose plastid is bounded by four membranes and still possesses a relict nucleus of a green algal endosymbiont (the nucleomorph) in the intermembrane space. We identified nine homologs of plant-like TOC/TIC components in the recently sequenced B. natans nuclear genome, adding to the two that remain in the nucleomorph genome ( B. natans TOC75 [BnTOC75] and BnTIC20). All of these proteins were predicted to be localized to the plastid and might function in the inner two membranes. We also show that the homologs of a protein, Der1, that is known to mediate transport across the second membrane in the several lineages with secondary plastids of red algal origin is not associated with plastid protein targeting in B. natans . How plastid proteins cross this membrane remains a mystery, but it is clear that the protein transport machinery of chlorarachniophyte plastids differs from that of red algal secondary plastids.
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Gölz, Peter, and Jürgen Feierabend. "Isoprenoid Biosynthesis and Stability in Developing Green and Achlorophyllous Leaves of Rye (Secale cereale L.)." Zeitschrift für Naturforschung C 48, no. 11-12 (December 1, 1993): 886–95. http://dx.doi.org/10.1515/znc-1993-11-1212.
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Formation of major prenylquinones and carotenoids was investigated by comparing the incorporation of [14C]mevalonate into segments of different age from green and etiolated leaves of 22 C-grown rye seedlings (Secale cereale L.) and from 32 C-grown rye leaves which contained bleached and proplastid-like ribosome-deficient plastids, due to a heat-sensitivity of 70S ribosome formation. The contents of plastidic isoprenoids were much lower (between 2 - 30%) in the achlorophyllous than in green leaves. In green leaves [14C]mevalonate incorporation into non-polar lipids and into plastoquinone was partially inhibited in the presence of gabaculin, an inhibitor of chlorophyll synthesis. However, except for β-carotene, [14C]mevalonate incorporation into isoprenoids continuously increased with age also in achlorophyllous etiolated or 32 °C-grown, as in green, leaves and was, except for P-carotene and plastoquinone, higher in etiolated than in green leaves. In bleached °32 C-grown leaves [14C]mevalonate incorporation into all plastidic isoprenoids was strikingly (up to 45-fold) higher than in green control leaves. While degradation of P-carotene was greatly enhanced in bleached 32 °C-grown leaves, relative to green control leaves, and could thus compensate for a higher apparent synthesis, chase experiments did not reveal any marked differences of the turnover of other isoprenoids. The half times of plastoquinone. phylloquinone and lutein were in the order of 2-3 days. Within a 24 h chase period a-tocopherol degradation did not become apparent. Uptake of [14C]mevalonate and [14C]isopentenyl pyrophosphate by isolated bleached plastids from 32 °C-grown leaves was much more rapid than by chloroplasts and resulted in higher precursor accumulation within the organelle. While mevalonate incorporation into isoprenoid lipids was not detected, isopentenyl pyrophosphate was incorporated into isoprenoid lipids, including plastoquinone. Rates of incorporation by isolated chloroplasts or bleached plastids were of similar order. The results illustrate that divergent types of plastid differentiation are associated with fundamental developmental changes of the metabolic flow of isoprenoid precursors between different products and compartments and, in particular, with changes of import into the plastid compartment.
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TANAKA, ICHIRO. "Microtubule-determined Plastid Distribution During Microsporogenesis in Lilium Longiflorum." Journal of Cell Science 99, no. 1 (May 1, 1991): 21–31. http://dx.doi.org/10.1242/jcs.99.1.21.
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The relationship between organelle distribution and the cytoskeleton was examined during microsporogenesis in Lilium longiflorum. The distribution pattern of plastid and mitochondrial nucleoids was followed by fluorescence microscopy after staining with 4′,6-diamidino-2-phenylindole (DAPI). Although the plastid nucleoids gradually enlarged during prophase I, by anaphase I of meiosis they were randomly distributed in the cytoplasm of each microsporocyte. At telophase I the plastid nucleoids were aggregated in the equatorial region of the cell. After entering prophase II the plastid nucleoids were randomly distributed in the cytoplasm, and at telophase II they had reaggregated to the equators of the two cells. After the completion of meiosis they were located at the two poles of each young microspore. This distinct cell polarity of plastid nucleoids was preserved in isolated protoplasts. In all cells where the distribution of plastid nucleoids was non-random, the nucleoids were invariably situated furthest away from the interphase and telophase nuclei. However, the distribution of mitochondrial nucleoids throughout meiotic division showed little cell polarity. Analysis of the microtubule and actin cytoskeletons during microsporogenesis revealed that the microtubules radiated out from the cell nuclei only at the stages when the distribution of plastids showed polarity, whereas the actin filaments were usually randomly oriented throughout the cytoplasm, independent of the plastid arrangement and of the organization of microtubule cytoskeleton. The radiating microtubules seemed to exclude the plastids from around the cell nuclei. Treatment of cultured pollen tetrads with colchicine disrupted the plastid polarity, probably by depolymerizing the radiating microtubules, resulting in a random distribution of the plastid nucleoids. Treatment with cytochalasin B, however, had no effect on the arrangement of plastids. These results demonstrate that microtubules function in the movement and distribution of plastids in male reproductive cells of higher plants. Further, it is assumed that the system of radiating microtubules that controls the distribution of plastids during male meiosis is also involved in the subsequent formation of male gametes, which are deficient in plastids in many angiosperm plants, including this lily.
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Chiu, W. L., and B. B. Sears. "Plastome-genome interactions affect plastid transmission in Oenothera." Genetics 133, no. 4 (April 1, 1993): 989–97. http://dx.doi.org/10.1093/genetics/133.4.989.
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Abstract Plastids of Oenothera, the evening primrose, can be transmitted to the progeny from both parents. In a constant nuclear background, the frequency of biparental plastid transmission is determined by the types of plastid genomes (plastomes) involved in the crosses. In this study, the impact of nuclear genomes on plastid inheritance was analyzed. In general, the transmission efficiency of each plastome correlated strongly with its compatibility with the nuclear genome of the progeny, suggesting that plastome-genome interactions can influence plastid transmission by affecting the efficiency of plastid multiplication after fertilization. Lower frequencies of plastid transmission from the paternal side were observed when the pollen had poor vigor due to an incompatible plastome-genome combination, indicating that plastome-genome interactions may also affect the input of plastids at fertilization. Parental traits that affect the process of fertilization can also have an impact on plastid transmission. Crosses using maternal parents with long styles or pollen with relatively low growth capacity resulted in reduced frequencies of paternal plastid transmission. These observations suggest that degeneration of pollen plastids may occur as the time interval between pollination and fertilization is lengthened.
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Brown, R. C., and B. E. Lemmon. "Morphogenetic plastid migration and spindle dynamics in simple land plants." Proceedings, annual meeting, Electron Microscopy Society of America 47 (August 6, 1989): 764–65. http://dx.doi.org/10.1017/s0424820100155797.
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In many of the simple land plants mitosis and/or meiosis occurs in cells that contain a single plastid. Preparation for division in these monoplastidic cells is especially obvious because of predictive migration and division of the single plastid. The plastids serve as foci for organization of spindle microtubules (Mts) resulting in infallible coordination of plastid and nuclear division. Thus unlike most plant cells where a distinct MTOC is difficult to distinguish, monoplastidic cells provide a system in which the material responsible for nucleating Mts is closely associated with the plastid envelope and can be followed throughout the cell cycle. The intimate association of plastids with spindle poles has suggested the concept of plastid polarity which holds that the behavior of plastids parallels that of animal centrosomes. This concept is supported by recent studies using correlated methods of modern botanical microscopy.Mitosis was studied in the basal meristem of hornwort sporophytes and in root tips of Isoetes and Selaginella.
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Zhu, T., H. L. Mogensen, and S. E. Smith. "Maternal plastids in alfalfa egg cells: A qualitative and quantitative study." Proceedings, annual meeting, Electron Microscopy Society of America 49 (August 1991): 210–11. http://dx.doi.org/10.1017/s0424820100085356.
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Genetic studies have shown that alfalfa (Medicago sativa L.) has a predominance of paternal plastid inheritance. Results from cytological studies, which have quantified plastids and plastid nucleoids within generative and sperm cells of alfalfa, demonstrate that male germ cell composition does not adequately explain known differences in patterns of plastid inheritance among specific genotypes. To determine the behavior and fate of female plastids, we are currently studying unfertilized eggs, zygotes and early embryos. Here we report preliminary results on the cytological composition of alfalfa egg cells in genotype, a relatively strong female plastid transmitter, and genotype CUFB, a relatively weak female.
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Patron, Nicola J., Matthew B. Rogers, and Patrick J. Keeling. "Gene Replacement of Fructose-1,6-Bisphosphate Aldolase Supports the Hypothesis of a Single Photosynthetic Ancestor of Chromalveolates." Eukaryotic Cell 3, no. 5 (October 2004): 1169–75. http://dx.doi.org/10.1128/ec.3.5.1169-1175.2004.
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ABSTRACT Plastids (photosynthetic organelles of plants and algae) are known to have spread between eukaryotic lineages by secondary endosymbiosis, that is, by the uptake of a eukaryotic alga by another eukaryote. But the number of times this has taken place is controversial. This is particularly so in the case of eukaryotes with plastids derived from red algae, which are numerous and diverse. Despite their diversity, it has been suggested that all these eukaryotes share a recent common ancestor and that their plastids originated in a single endosymbiosis, the so-called “chromalveolate hypothesis.” Here we describe a novel molecular character that supports the chromalveolate hypothesis. Fructose-1,6-bisphosphate aldolase (FBA) is a glycolytic and Calvin cycle enzyme that exists as two nonhomologous types, class I and class II. Red algal plastid-targeted FBA is a class I enzyme related to homologues from plants and green algae, and it would be predicted that the plastid-targeted FBA from algae with red algal secondary endosymbionts should be related to this class I enzyme. However, we show that plastid-targeted FBA of heterokonts, cryptomonads, haptophytes, and dinoflagellates (all photosynthetic chromalveolates) are class II plastid-targeted enzymes, completely unlike those of red algal plastids. The chromalveolate enzymes form a strongly supported group in FBA phylogeny, and their common possession of this unexpected plastid characteristic provides new evidence for their close relationship and a common origin for their plastids.
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Ku, Chuan, Mayo Roettger, Verena Zimorski, Shijulal Nelson-Sathi, Filipa L. Sousa, and William F. Martin. "Plastid origin: who, when and why?" Acta Societatis Botanicorum Poloniae 83, no. 4 (2014): 281–89. http://dx.doi.org/10.5586/asbp.2014.045.
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The origin of plastids is best explained by endosymbiotic theory, which dates back to the early 1900s. Three lines of evidence based on protein import machineries and molecular phylogenies of eukaryote (host) and cyanobacterial (endosymbiont) genes point to a single origin of primary plastids, a unique and important event that successfully transferred two photosystems and oxygenic photosynthesis from prokaryotes to eukaryotes. The nature of the cyanobacterial lineage from which plastids originated has been a topic of investigation. Recent studies have focused on the branching position of the plastid lineage in the phylogeny based on cyanobacterial core genes, that is, genes shared by all cyanobacteria and plastids. These studies have delivered conflicting results, however. In addition, the core genes represent only a very small portion of cyanobacterial genomes and may not be a good proxy for the rest of the ancestral plastid genome. Information in plant nuclear genomes, where most genes that entered the eukaryotic lineage through acquisition from the plastid ancestor reside, suggests that heterocyst-forming cyanobacteria in Stanier’s sections IV and V are most similar to the plastid ancestor in terms of gene complement and sequence conservation, which is in agreement with models suggesting an important role of nitrogen fixation in symbioses involving cyanobacteria. Plastid origin is an ancient event that involved a prokaryotic symbiont and a eukaryotic host, organisms with different histories and genome evolutionary processes. The different modes of genome evolution in prokaryotes and eukaryotes bear upon our interpretations of plastid phylogeny.
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Oross, J. W., and J. V. Possingham. "Tubular structures in developing plastids of three dicotyledonous species." Canadian Journal of Botany 69, no. 1 (January 1, 1991): 136–39. http://dx.doi.org/10.1139/b91-019.
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Tubular structures were observed in the developing plastids of the meristematic regions of spinach, beet, and turnip leaves. These structures were located near the plastid periphery, were frequently in contact with the plastid envelope and (or) the internal plastic membranes, usually had a near-perpendicular orientation with their associated membranes, and were decorated with a distinct striated coating. Based on the high degree of structural similarity, it was suggested that these tubules represent a unique class of plastid inclusions with a common specialized function. A detailed examination of the spinach plastids provided evidence that the tubules are membranous structures and that the tubular lumen is confluent with that of the plastid envelope and also some internal plastidial compartments. It was also shown that the membranes of the tubules differed from the other plastidial membranes in that they were thinner and only lightly stained by osmium – potassium ferrocyanide postfixation. Key words: tubular, structures, developing, plastids, dicots.
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Keeling, Patrick J. "The endosymbiotic origin, diversification and fate of plastids." Philosophical Transactions of the Royal Society B: Biological Sciences 365, no. 1541 (March 12, 2010): 729–48. http://dx.doi.org/10.1098/rstb.2009.0103.
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Plastids and mitochondria each arose from a single endosymbiotic event and share many similarities in how they were reduced and integrated with their host. However, the subsequent evolution of the two organelles could hardly be more different: mitochondria are a stable fixture of eukaryotic cells that are neither lost nor shuffled between lineages, whereas plastid evolution has been a complex mix of movement, loss and replacement. Molecular data from the past decade have substantially untangled this complex history, and we now know that plastids are derived from a single endosymbiotic event in the ancestor of glaucophytes, red algae and green algae (including plants). The plastids of both red algae and green algae were subsequently transferred to other lineages by secondary endosymbiosis. Green algal plastids were taken up by euglenids and chlorarachniophytes, as well as one small group of dinoflagellates. Red algae appear to have been taken up only once, giving rise to a diverse group called chromalveolates. Additional layers of complexity come from plastid loss, which has happened at least once and probably many times, and replacement. Plastid loss is difficult to prove, and cryptic, non-photosynthetic plastids are being found in many non-photosynthetic lineages. In other cases, photosynthetic lineages are now understood to have evolved from ancestors with a plastid of different origin, so an ancestral plastid has been replaced with a new one. Such replacement has taken place in several dinoflagellates (by tertiary endosymbiosis with other chromalveolates or serial secondary endosymbiosis with a green alga), and apparently also in two rhizarian lineages: chlorarachniophytes and Paulinella (which appear to have evolved from chromalveolate ancestors). The many twists and turns of plastid evolution each represent major evolutionary transitions, and each offers a glimpse into how genomes evolve and how cells integrate through gene transfers and protein trafficking.
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Sobanski, Johanna, Patrick Giavalisco, Axel Fischer, Julia M. Kreiner, Dirk Walther, Mark Aurel Schöttler, Tommaso Pellizzer, et al. "Chloroplast competition is controlled by lipid biosynthesis in evening primroses." Proceedings of the National Academy of Sciences 116, no. 12 (March 4, 2019): 5665–74. http://dx.doi.org/10.1073/pnas.1811661116.
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In most eukaryotes, organellar genomes are transmitted preferentially by the mother, but molecular mechanisms and evolutionary forces underlying this fundamental biological principle are far from understood. It is believed that biparental inheritance promotes competition between the cytoplasmic organelles and allows the spread of so-called selfish cytoplasmic elements. Those can be, for example, fast-replicating or aggressive chloroplasts (plastids) that are incompatible with the hybrid nuclear genome and therefore maladaptive. Here we show that the ability of plastids to compete against each other is a metabolic phenotype determined by extremely rapidly evolving genes in the plastid genome of the evening primroseOenothera. Repeats in the regulatory region ofaccD(the plastid-encoded subunit of the acetyl-CoA carboxylase, which catalyzes the first and rate-limiting step of lipid biosynthesis), as well as inycf2(a giant reading frame of still unknown function), are responsible for the differences in competitive behavior of plastid genotypes. Polymorphisms in these genes influence lipid synthesis and most likely profiles of the plastid envelope membrane. These in turn determine plastid division and/or turnover rates and hence competitiveness. This work uncovers cytoplasmic drive loci controlling the outcome of biparental chloroplast transmission. Here, they define the mode of chloroplast inheritance, as plastid competitiveness can result in uniparental inheritance (through elimination of the “weak” plastid) or biparental inheritance (when two similarly “strong” plastids are transmitted).
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Dorrell, Richard G., Tomonori Azuma, Mami Nomura, Guillemette Audren de Kerdrel, Lucas Paoli, Shanshan Yang, Chris Bowler, et al. "Principles of plastid reductive evolution illuminated by nonphotosynthetic chrysophytes." Proceedings of the National Academy of Sciences 116, no. 14 (March 14, 2019): 6914–23. http://dx.doi.org/10.1073/pnas.1819976116.
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The division of life into producers and consumers is blurred by evolution. For example, eukaryotic phototrophs can lose the capacity to photosynthesize, although they may retain vestigial plastids that perform other essential cellular functions. Chrysophyte algae have undergone a particularly large number of photosynthesis losses. Here, we present a plastid genome sequence from a nonphotosynthetic chrysophyte, “Spumella” sp. NIES-1846, and show that it has retained a nearly identical set of plastid-encoded functions as apicomplexan parasites. Our transcriptomic analysis of 12 different photosynthetic and nonphotosynthetic chrysophyte lineages reveals remarkable convergence in the functions of these nonphotosynthetic plastids, along with informative lineage-specific retentions and losses. At one extreme,Cornospumella fuschlensisretains many photosynthesis-associated proteins, although it appears to have lost the reductive pentose phosphate pathway and most plastid amino acid metabolism pathways. At the other extreme,Paraphysomonaslacks plastid-targeted proteins associated with gene expression and all metabolic pathways that require plastid-encoded partners, indicating a complete loss of plastid DNA in this genus. Intriguingly, some of the nucleus-encoded proteins that once functioned in the expression of theParaphysomonasplastid genome have been retained. These proteins were likely to have been dual targeted to the plastid and mitochondria of the chrysophyte ancestor, and are uniquely targeted to the mitochondria inParaphysomonas. Our comparative analyses provide insights into the process of functional reduction in nonphotosynthetic plastids.
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Ahmad, Niaz, and Brent L. Nielsen. "Plastid Transcriptomics: An Important Tool For Plastid Functional Genomics." Protein & Peptide Letters 28, no. 8 (September 10, 2021): 855–60. http://dx.doi.org/10.2174/0929866528999210128210555.
Full textAbstract:
Plastids in higher plants carry out specialized roles such as photosynthesis, nitrogen assimilation, biosynthesis of amino acids, fatty acids, isoprenoids, and various metabolites. Plastids arise from undifferentiated precursors known as proplastids, which are found in the root and shoot meristems. They are highly dynamic as they change their number, morphology, and physiology according to the tissue they are present. In addition to housing various metabolic activities, plastids also serve as a global sensor for both internal and external environmental cues including different stresses, and help plants to respond/adjust accordingly. They relay information to the nucleus, which then responds by changing the expression levels of specific genes. It has been shown that plants with impaired plastid functions exhibit abnormalities. One of the sources emanating these signals to the nucleus is plastid transcription. Normal plastid functioning is therefore critical for plant survival. Despite immense significance for plant acclimation, the plastid transcriptome is largely an unstudied research area. In this review, we discuss the importance of plastid transcriptomics for the acclimation of plants under changing environmental conditions and summarize the key literature published in this field.
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Gornik, Sebastian G., Febrimarsa, Andrew M. Cassin, James I. MacRae, Abhinay Ramaprasad, Zineb Rchiad, Malcolm J. McConville, et al. "Endosymbiosis undone by stepwise elimination of the plastid in a parasitic dinoflagellate." Proceedings of the National Academy of Sciences 112, no. 18 (April 20, 2015): 5767–72. http://dx.doi.org/10.1073/pnas.1423400112.
Full textAbstract:
Organelle gain through endosymbiosis has been integral to the origin and diversification of eukaryotes, and, once gained, plastids and mitochondria seem seldom lost. Indeed, discovery of nonphotosynthetic plastids in many eukaryotes—notably, the apicoplast in apicomplexan parasites such as the malaria pathogen Plasmodium—highlights the essential metabolic functions performed by plastids beyond photosynthesis. Once a cell becomes reliant on these ancillary functions, organelle dependence is apparently difficult to overcome. Previous examples of endosymbiotic organelle loss (either mitochondria or plastids), which have been invoked to explain the origin of eukaryotic diversity, have subsequently been recognized as organelle reduction to cryptic forms, such as mitosomes and apicoplasts. Integration of these ancient symbionts with their hosts has been too well developed to reverse. Here, we provide evidence that the dinoflagellate Hematodinium sp., a marine parasite of crustaceans, represents a rare case of endosymbiotic organelle loss by the elimination of the plastid. Extensive RNA and genomic sequencing data provide no evidence for a plastid organelle, but, rather, reveal a metabolic decoupling from known plastid functions that typically impede organelle loss. This independence has been achieved through retention of ancestral anabolic pathways, enzyme relocation from the plastid to the cytosol, and metabolic scavenging from the parasite’s host. Hematodinium sp. thus represents a further dimension of endosymbiosis—life after the organelle.
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Kohler, R. H., P. Schwille, W. W. Webb, and M. R. Hanson. "Active protein transport through plastid tubules: velocity quantified by fluorescence correlation spectroscopy." Journal of Cell Science 113, no. 22 (November 15, 2000): 3921–30. http://dx.doi.org/10.1242/jcs.113.22.3921.
Full textAbstract:
Dynamic tubular projections emanate from plastids in certain cells of vascular plants and are especially prevalent in non-photosynthetic cells. Tubules sometimes connect two or more different plastids and can extend over long distances within a cell, observations that suggest that the tubules may function in distribution of molecules within, to and from plastids. In a new application of two-photon excitation (2PE) fluorescence correlation spectroscopy (FCS), we separated diffusion of fluorescent molecules from active transport in vivo. We quantified the velocities of diffusion versus active transport of green fluorescent protein (GFP) within plastid tubules and in the cytosol in vivo. GFP moves by 3-dimensional (3-D) diffusion both in the cytosol and plastid tubules, but diffusion in tubules is about 50 times and 100 times slower than in the cytosol and an aqueous solution, respectively. Unexpectedly larger GFP units within plastid tubules exhibited active transport with a velocity of about 0.12 microm/second. Active transport might play an important role in the long-distance distribution of large numbers of molecules within the highly viscous stroma of plastid tubules.
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Coleman, A. W., and M. J. Maguire. "Fluorescence microscopy and image analysis studies showing how plastids grow." Proceedings, annual meeting, Electron Microscopy Society of America 47 (August 6, 1989): 782–83. http://dx.doi.org/10.1017/s0424820100155888.
Full textAbstract:
Biochemical analyses have shown that leaf plastid material/cell, both genomes and other materials, increase during growth and in response to light and other cues. However, the biochemical methods inevitably express results as an average per cell, leaving the precise timing of events in the cell cycle and course of ontogeny uncertain, and the variation in guantity/cell largely unknown. The power of quantitative microscopy lies in the capability of determining information on the single cell or single plastid level.To test the feasibility of using microscopic methods to study plastid growth and variability, we chose as an analog of the plant meristematic cell, the photosynthetic alga Ochromonas danica. This unicellular Chrysophyte combines a number of advantageous features. It typically has but 1-2 plastids and these occupy only a small proportion of the cell volume. Secondly, Ochromonas grows rapidly both in light and in darkness to high cell densities. Thirdly, the cell lacks a wall, so that its contents can be examined in detail in living cells flattened beneath a coverslip. Thirdly, the organism synthesizes chlorophyll both in light and darkness, so that plastids in living cells, however small, can be distinguished by virtue of the autofluorescence of their chlorophyll. Finally, for measurement of DNA per plastid, the arrangement of plastid DNA in Ochromonas plastids, as a necklace closely underlying the perimeter of the plastid, ensures that when one has isolated, stained intact necklaces, one is measuring the entire DNA content of the plastid.
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Burki, Fabien, Behzad Imanian, Elisabeth Hehenberger, Yoshihisa Hirakawa, Shinichiro Maruyama, and Patrick J. Keeling. "Endosymbiotic Gene Transfer in Tertiary Plastid-Containing Dinoflagellates." Eukaryotic Cell 13, no. 2 (December 2, 2013): 246–55. http://dx.doi.org/10.1128/ec.00299-13.
Full textAbstract:
ABSTRACTPlastid establishment involves the transfer of endosymbiotic genes to the host nucleus, a process known as endosymbiotic gene transfer (EGT). Large amounts of EGT have been shown in several photosynthetic lineages but also in present-day plastid-lacking organisms, supporting the notion that endosymbiotic genes leave a substantial genetic footprint in the host nucleus. Yet the extent of this genetic relocation remains debated, largely because the long period that has passed since most plastids originated has erased many of the clues to how this process unfolded. Among the dinoflagellates, however, the ancestral peridinin-containing plastid has been replaced by tertiary plastids on several more recent occasions, giving us a less ancient window to examine plastid origins. In this study, we evaluated the endosymbiotic contribution to the host genome in two dinoflagellate lineages with tertiary plastids. We generated the first nuclear transcriptome data sets for the “dinotoms,” which harbor diatom-derived plastids, and analyzed these data in combination with the available transcriptomes for kareniaceans, which harbor haptophyte-derived plastids. We found low level of detectable EGT in both dinoflagellate lineages, with only 9 genes and 90 genes of possible tertiary endosymbiotic origin in dinotoms and kareniaceans, respectively, suggesting that tertiary endosymbioses did not heavily impact the host dinoflagellate genomes.
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Schwuchow, Jochen, and Fred D. Sack. "Effects of inversion on plastid position and gravitropism in Ceratodon protonemata." Canadian Journal of Botany 71, no. 9 (September 1, 1993): 1243–48. http://dx.doi.org/10.1139/b93-147.
Full textAbstract:
When dark-grown tip cells of protonemata of the moss Ceratodon purpureus are turned to the horizontal, plastids first sediment towards gravity in a specific zone and then the cell tip curves upward. To determine whether gravitropism and plastid sedimentation occur in other orientations, protonemata were reoriented to angles other than 90°. Qualitative and quantitative light microscopic observations show that plastid sedimentation along the cell axis occurs in both upright and inverted cells. However, only some plastids fall and sedimentation is incomplete; plastids remain distributed throughout the length of the cell, and those plastids that sediment do not fall all the way to the bottom of the cell. Tip cells are gravitropic regardless of stimulation angle, and as in higher plants, the maximal rate of initial curvature is in response to a 120° reorientation. Infrared videomicroscopy, time-lapse studies of living, inverted protonemata indicate that amyloplast sedimentation precedes upward curvature. Together, these data further support (i) the hypothesis that amyloplast sedimentation functions in gravitropic sensing in these cells, and (ii) the idea that gravity affected the evolution of cell organization. Key words: gravitropism, inversion, plastid sedimentation, protonema, moss.
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Shrestha, Bikash, Lawrence E. Gilbert, Tracey A. Ruhlman, and Robert K. Jansen. "Clade-Specific Plastid Inheritance Patterns Including Frequent Biparental Inheritance in Passiflora Interspecific Crosses." International Journal of Molecular Sciences 22, no. 5 (February 25, 2021): 2278. http://dx.doi.org/10.3390/ijms22052278.
Full textAbstract:
Plastid inheritance in angiosperms is presumed to be largely maternal, with the potential to inherit plastids biparentally estimated for about 20% of species. In Passiflora, maternal, paternal and biparental inheritance has been reported; however, these studies were limited in the number of crosses and progeny examined. To improve the understanding of plastid transmission in Passiflora, the progeny of 45 interspecific crosses were analyzed in the three subgenera: Passiflora, Decaloba and Astrophea. Plastid types were assessed following restriction digestion of PCR amplified plastid DNA in hybrid embryos, cotyledons and leaves at different developmental stages. Clade-specific patterns of inheritance were detected such that hybrid progeny from subgenera Passiflora and Astrophea predominantly inherited paternal plastids with occasional incidences of maternal inheritance, whereas subgenus Decaloba showed predominantly maternal and biparental inheritance. Biparental plastid inheritance was also detected in some hybrids from subgenus Passiflora. Heteroplasmy due to biparental inheritance was restricted to hybrid cotyledons and first leaves with a single parental plastid type detectable in mature plants. This indicates that in Passiflora, plastid retention at later stages of plant development may not reflect the plastid inheritance patterns in embryos. Passiflora exhibits diverse patterns of plastid inheritance, providing an excellent system to investigate underlying mechanisms in angiosperms.
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Waller, Ross F., Nicola J. Patron, and Patrick J. Keeling. "Phylogenetic history of plastid-targeted proteins in the peridinin-containing dinoflagellate Heterocapsa triquetra." International Journal of Systematic and Evolutionary Microbiology 56, no. 6 (June 1, 2006): 1439–47. http://dx.doi.org/10.1099/ijs.0.64061-0.
Full textAbstract:
The evolutionary history and relationship between plastids of dinoflagellate algae and apicomplexan parasites have been controversial both because the organelles are unusual and because their genomes contain few comparable genes. However, most plastid proteins are encoded in the host nucleus and targeted to the organelle, and several of these genes have proved to have interesting and informative evolutionary histories. We have used expressed sequence tag (EST) sequencing to generate gene sequence data from the nuclear genome of the dinoflagellate Heterocapsa triquetra and inferred phylogenies for the complete set of identified plastid-targeted proteins. Overall, dinoflagellate plastid proteins are most consistently related to homologues from the red algal plastid lineage (not green) and, in many of the most robust cases, they branch with other chromalveolate algae. In resolved phylogenies where apicomplexan data are available, dinoflagellates and apicomplexans are related. We also identified two cases of apparent lateral, or horizontal, gene transfer, one from the green plastid lineage and one from a bacterial lineage unrelated to plastids or cyanobacteria.
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Renzaglia, Karen Sue, Angel R. Maden, Jeffrey G. Duckett, and Dean P. Whittier. "Monoplastidy in spermatogenesis of Lycopodium obscurum." Canadian Journal of Botany 72, no. 10 (October 1, 1994): 1436–44. http://dx.doi.org/10.1139/b94-177.
Full textAbstract:
Unlike Lycopodium laterale, which is polyplastidic during spermatogenesis, Lycopodium obscurum exhibits monoplastidy beginning in the early proliferative stages of antheridial development. Previous cell generations are polyplastidic and plastid fusion involving connective cylinders establishes the monoplastidic condition. Plastid and nuclear divisions are coordinated in L. obscurum with the plastids positioned at opposite poles prior to spindle development. Unlike monoplastidic cell divisions with morphogenetic plastid migration and polarity in other lycophytes, mosses, and hornworts, however, the spindles in L. obscurum do not originate from the plastid envelopes but from endoplasmic reticulum positioned against the plastid. In the final divisions, spindle microtubules emanate from structurally defined microtubule organizing centers that develop between the plastids and nucleus. Preceding the appearance of centrioles in the spermatid mother cell, the centrosomes comprise electron-dense granular matrices with associated vesicles and endoplasmic reticulum. Among archegoniate microtubule organizing centers, the discrete acentriolar centrosomes of Lycopodium most closely resemble the microtubule organizing centers in moss spore development and the polar organizer of liverwort mitosis. Key words: annulate lamellae, centrosome, Lycopodium, microtubule organizing center, monoplastidy, plastid dividing ring.
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Howe, Christopher J., Adrian C. Barbrook, V. Lila Koumandou, R. Ellen R. Nisbet, Hamish A. Symington, and Tom F. Wightman. "Evolution of the chloroplast genome." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 358, no. 1429 (January 29, 2003): 99–107. http://dx.doi.org/10.1098/rstb.2002.1176.
Full textAbstract:
We discuss the suggestion that differences in the nucleotide composition between plastid and nuclear genomes may provide a selective advantage in the transposition of genes from plastid to nucleus. We show that in the adenine, thymine (AT)–rich genome of Borrelia burgdorferi several genes have an AT–content lower than the average for the genome as a whole. However, genes whose plant homologues have moved from plastid to nucleus are no less AT–rich than genes whose plant homologues have remained in the plastid, indicating that both classes of gene are able to support a high AT–content. We describe the anomalous organization of dinoflagellate plastid genes. These are located on small circles of 2–3 kbp, in contrast to the usual plastid genome organization of a single large circle of 100–200 kbp. Most circles contain a single gene. Some circles contain two genes and some contain none. Dinoflagellate plastids have retained far fewer genes than other plastids. We discuss a similarity between the dinoflagellate minicircles and the bacterial integron system.
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Robertson, E. J., K. A. Pyke, and R. M. Leech. "arc6, an extreme chloroplast division mutant of Arabidopsis also alters proplastid proliferation and morphology in shoot and root apices." Journal of Cell Science 108, no. 9 (September 1, 1995): 2937–44. http://dx.doi.org/10.1242/jcs.108.9.2937.
Full textAbstract:
The arc6 (accumulation and replication of chloroplasts) mutant of Arabidopsis has only two greatly enlarged chloroplasts per mature leaf mesophyll cell compared with ninety chloroplasts per cell in the wild type. The mutation is a single nuclear gene and the plant phenotype is normal. Shoot and root apical meristems of arc6 plants have been examined to determine how early during plastid development the mutant arc6 phenotype can be recognised. In the cells of the arc6 apical meristem there are only two proplastids, which are larger than wild type with a highly variable morphology. In the cells of the leaf primordia where differentiation of proplastids to chloroplasts occurs arc6 plastids are larger and at a more advanced developmental stage than wild-type plastids. In arc6 root cells statoliths and other plastids also show grossly abnormal morphology and the statoliths are greatly increased in size. During arc6 stomatal guard cell development the perturbation in proplastid population dynamics affects plastid segregation and 30% of stomata lack plastids in one or both guard cells. Our evidence would suggest that ARC6 is expressed throughout the vegetative cells of the Arabidopsis seedling with major effects on both the proplastid phenotype and the proplastid population. ARC6 is the first gene to be identified in Arabidopsis which has a global effect on plastid development in cells arising from both the shoot and root meristems, and is of major importance in the nuclear control of plastid differentiation in higher plants.
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Maple, Jodi, and Simon Geir Møller. "The complexity and evolution of the plastid-division machinery." Biochemical Society Transactions 38, no. 3 (May 24, 2010): 783–88. http://dx.doi.org/10.1042/bst0380783.
Full textAbstract:
Plastids are vital organelles, fulfilling important metabolic functions that greatly influence plant growth and productivity. In order to both regulate and harness the metabolic output of plastids, it is vital that the process of plastid division is carefully controlled. This is essential, not only to ensure persistence in dividing plant cells and that optimal numbers of plastids are obtained in specialized cell types, but also to allow the cell to act in response to developmental signals and environmental changes. How this control is exerted by the host nucleus has remained elusive. Plastids evolved by endosymbiosis and during the establishment of a permanent endosymbiosis they retained elements of the bacterial cell-division machinery. Through evolution the photosynthetic eukaryotes have increased dramatically in complexity, from single-cell green algae to multicellular non-vascular and vascular plants. Reflected with this is an increasing complexity of the division machinery and recent findings also suggest increasing complexity in the molecular mechanisms used by the host cell to control the process of plastid division. In the present paper, we explore the current understanding of the process of plastid division at the molecular and cellular level, with particular respect to the evolution of the division machinery and levels of control exerted on the process.
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BUSBY, C. H., and B. E. GUNNING. "Development of the quadripolar meiotic apparatus in Funaria spore mother cells: analysis by means of anti-microtubule drug treatments." Journal of Cell Science 93, no. 2 (June 1, 1989): 267–77. http://dx.doi.org/10.1242/jcs.93.2.267.
Full textAbstract:
Microtubule-dependent processes in Funaria hygrometrica spore mother cells (SMCs) were analysed by monitoring the effects of colchicine and oryzalin on pre-meiotic and meiotic events. The techniques used were electron microscopy, immunofluorescence microscopy of microtubules (MTs)and continuous video recording of events in treated and recovering live cells sampled at various stages of sporogenesis. Inferences drawn from previous work that the SMC plastids serve as MT-organizing centres were confirmed in so far as MT recovery in MT-depleted cells starts at the tips of the plastids. The MTs that emanate from these regions are required for positioning the plastids in the tetrahedral conformation, which defines the meiotic poles, for positioning lipid droplets in clusters at these poles and for positioning and holding the nucleus in the tetrahedral cage. If released, the nucleus can be moved by a non-MT system. Other phenomena not controlled by MTs are plastid elongation, maintenance of the tetrahedral conformation-when the MTs are absent (during divisions or as a result of drug treatment) and (probably) development of the organelle band that spans the cell between divisions I and II. In cells treated during division, when there is nonuclear envelope, the pattern of MT recovery is different: the plastids are inactive as microtubule-organizing centres (MTOCs) but MTs reappear among the chromosomes. Spindles capable of transporting chromosomes regenerate. However, the importance of interactions between nucleus and plastids is highlighted by cases in which treatmenthas resulted in: (1) movement of the nucleus out of the quadripolar plastid cage; and (2) loss of the MTs at plastid tips that normally contribute to the spindle poles; in such cases quadripolarity is lost even though functional spindles return. Plastid MTOC activity returns when the nuclear envelope isin place, i.e. in interkinesis and after telophase II.
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Ivanova, Yordanka, Matthew D. Smith, Kunhua Chen, and Danny J. Schnell. "Members of the Toc159 Import Receptor Family Represent Distinct Pathways for Protein Targeting to Plastids." Molecular Biology of the Cell 15, no. 7 (July 2004): 3379–92. http://dx.doi.org/10.1091/mbc.e03-12-0923.
Full textAbstract:
Plastids represent a diverse group of organelles that perform essential metabolic and signaling functions within all plant cells. The differentiation of specific plastid types relies on the import of selective sets of proteins from among the ∼2500 nucleus-encoded plastid proteins. The Toc159 family of GTPases mediates the initial targeting of proteins to plastids. In Arabidopsis thaliana, the Toc159 family consists of four genes: atTOC159, atTOC132, atTOC120, and atTOC90. In vivo analysis of atToc159 function indicates that it is required specifically for the import of proteins necessary for chloroplast biogenesis. In this report, we demonstrate that atToc120 and atToc132 represent a structurally and functionally unique subclass of protein import receptors. Unlike atToc159, mutants lacking both atToc120 and atToc132 are inviable. Furthermore, atToc120 and atToc132 exhibit preprotein binding properties that are distinct from atToc159. These data indicate that the different members of the Toc159 family represent distinct pathways for protein targeting to plastids and are consistent with the hypothesis that separate pathways have evolved to ensure balanced import of essential proteins during plastid development.
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Hehenberger, Elisabeth, Rebecca J. Gast, and Patrick J. Keeling. "A kleptoplastidic dinoflagellate and the tipping point between transient and fully integrated plastid endosymbiosis." Proceedings of the National Academy of Sciences 116, no. 36 (August 19, 2019): 17934–42. http://dx.doi.org/10.1073/pnas.1910121116.
Full textAbstract:
Plastid endosymbiosis has been a major force in the evolution of eukaryotic cellular complexity, but how endosymbionts are integrated is still poorly understood at a mechanistic level. Dinoflagellates, an ecologically important protist lineage, represent a unique model to study this process because dinoflagellate plastids have repeatedly been reduced, lost, and replaced by new plastids, leading to a spectrum of ages and integration levels. Here we describe deep-transcriptomic analyses of the Antarctic Ross Sea dinoflagellate (RSD), which harbors long-term but temporary kleptoplasts stolen from haptophyte prey, and is closely related to dinoflagellates with fully integrated plastids derived from different haptophytes. In some members of this lineage, called the Kareniaceae, their tertiary haptophyte plastids have crossed a tipping point to stable integration, but RSD has not, and may therefore reveal the order of events leading up to endosymbiotic integration. We show that RSD has retained its ancestral secondary plastid and has partitioned functions between this plastid and the kleptoplast. It has also obtained genes for kleptoplast-targeted proteins via horizontal gene transfer (HGT) that are not derived from the kleptoplast lineage. Importantly, many of these HGTs are also found in the related species with fully integrated plastids, which provides direct evidence that genetic integration preceded organelle fixation. Finally, we find that expression of kleptoplast-targeted genes is unaffected by environmental parameters, unlike prey-encoded homologs, suggesting that kleptoplast-targeted HGTs have adapted to posttranscriptional regulation mechanisms of the host.
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Araus, J. L., J. Sabidó, and F. J. Aguilá. "Structural Differences between Green and White Sectors of Variegated Scindapsus aureus Leaves." Journal of the American Society for Horticultural Science 111, no. 1 (January 1986): 98–102. http://dx.doi.org/10.21273/jashs.111.1.98.
Full textAbstract:
Abstract Several anatomical and ultrastructural features, as well as some related physiological parameters, have been studied in green and white sectors of Scindapsus aureus variegated leaves. Incidence of structural variations in dark respiration rates of leaves also has been considered. Total chlorophyll content of white sectors is about 2% that of green ones. Dark respiration rate in white sectors is about half that measured in green sectors. There are no differences anatomically between both types of sectors. Plastid number and plastid long axis length are greater in green than in white sectors. Such differences explain why the plastid area to leaf area ratio in white sectors is about half that of green sectors. This ratio has been related to differences in dark respiration rate between green and white sectors. Mutant plastids are typical photobleaching mutants. There seems to be a good correspondence with Knoth's model for plastid degeneration. Mutant plastids have an extensive system of peripheral reticula.
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Jeran, Nicolaj, Lisa Rotasperti, Giorgia Frabetti, Anna Calabritto, Paolo Pesaresi, and Luca Tadini. "The PUB4 E3 Ubiquitin Ligase Is Responsible for the Variegated Phenotype Observed upon Alteration of Chloroplast Protein Homeostasis in Arabidopsis Cotyledons." Genes 12, no. 9 (September 6, 2021): 1387. http://dx.doi.org/10.3390/genes12091387.
Full textAbstract:
During a plant’s life cycle, plastids undergo several modifications, from undifferentiated pro-plastids to either photosynthetically-active chloroplasts, ezioplasts, chromoplasts or storage organelles, such as amyloplasts, elaioplasts and proteinoplasts. Plastid proteome rearrangements and protein homeostasis, together with intracellular communication pathways, are key factors for correct plastid differentiation and functioning. When plastid development is affected, aberrant organelles are degraded and recycled in a process that involves plastid protein ubiquitination. In this study, we have analysed the Arabidopsis gun1-102 ftsh5-3 double mutant, lacking both the plastid-located protein GUN1 (Genomes Uncoupled 1), involved in plastid-to-nucleus communication, and the chloroplast-located FTSH5 (Filamentous temperature-sensitive H5), a metalloprotease with a role in photosystem repair and chloroplast biogenesis. gun1-102 ftsh5-3 seedlings show variegated cotyledons and true leaves that we attempted to suppress by introgressing second-site mutations in genes involved in: (i) plastid translation, (ii) plastid folding/import and (iii) cytosolic protein ubiquitination. Different phenotypic effects, ranging from seedling-lethality to partial or complete suppression of the variegated phenotype, were observed in the corresponding triple mutants. Our findings indicate that Plant U-Box 4 (PUB4) E3 ubiquitin ligase plays a major role in the target degradation of damaged chloroplasts and is the main contributor to the variegated phenotype observed in gun1-102 ftsh5-3 seedlings.
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Hempel, Franziska, Andrew Bozarth, Maik S. Sommer, Stefan Zauner, Jude M. Przyborski, and Uwe-G. Maier. "Transport of nuclear-encoded proteins into secondarily evolved plastids." Biological Chemistry 388, no. 9 (September 1, 2007): 899–906. http://dx.doi.org/10.1515/bc.2007.119.
Full textAbstract:
Abstract Many algal groups evolved by engulfment and intracellular reduction of a eukaryotic phototroph within a heterotrophic cell. Via this process, so-called secondary plastids evolved, surrounded by three or four membranes. In these organisms most of the genetic material encoding plastid functions is localized in the cell nucleus, with the result that many proteins have to pass three, four, or even five membranes to reach their final destination within the plastid. In this article, we review recent models and findings that help to explain important cellular mechanisms involved in the complex process of protein transport into secondary plastids.
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Salomaki, Eric, and Martin Kolisko. "There Is Treasure Everywhere: Reductive Plastid Evolution in Apicomplexa in Light of Their Close Relatives." Biomolecules 9, no. 8 (August 19, 2019): 378. http://dx.doi.org/10.3390/biom9080378.
Full textAbstract:
The phylum Apicomplexa (Alveolates) comprises a group of host-associated protists, predominately intracellular parasites, including devastating parasites like Plasmodium falciparum, the causative agent of malaria. One of the more fascinating characteristics of Apicomplexa is their highly reduced (and occasionally lost) remnant plastid, termed the apicoplast. Four core metabolic pathways are retained in the apicoplast: heme synthesis, iron–sulfur cluster synthesis, isoprenoid synthesis, and fatty acid synthesis. It has been suggested that one or more of these pathways are essential for plastid and plastid genome retention. The past decade has witnessed the discovery of several apicomplexan relatives, and next-generation sequencing efforts are revealing that they retain variable plastid metabolic capacities. These data are providing clues about the core genes and pathways of reduced plastids, while at the same time further confounding our view on the evolutionary history of the apicoplast. Here, we examine the evolutionary history of the apicoplast, explore plastid metabolism in Apicomplexa and their close relatives, and propose that the differences among reduced plastids result from a game of endosymbiotic roulette. Continued exploration of the Apicomplexa and their relatives is sure to provide new insights into the evolution of the apicoplast and apicomplexans as a whole.
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Lu, Pengjun, Ruqian Wang, Changqing Zhu, Xiumin Fu, Shasha Wang, Don Grierson, and Changjie Xu. "Microscopic Analyses of Fruit Cell Plastid Development in Loquat (Eriobotrya japonica) during Fruit Ripening." Molecules 24, no. 3 (January 27, 2019): 448. http://dx.doi.org/10.3390/molecules24030448.
Full textAbstract:
Plastids are sites for carotenoid biosynthesis and accumulation, but detailed information on fruit plastid development and its relation to carotenoid accumulation remains largely unclear. Here, using Baisha (BS; white-fleshed) and Luoyangqing (LYQ; red-fleshed) loquat (Eriobotrya japonica), a detailed microscopic analysis of plastid development during fruit ripening was carried out. In peel cells, chloroplasts turned into smaller chromoplasts in both cultivars, and the quantity of plastids in LYQ increased by one-half during fruit ripening. The average number of chromoplasts per peel cell in fully ripe fruit was similar between the two cultivars, but LYQ peel cell plastids were 20% larger and had a higher colour density, associated with the presence of larger plastoglobules. In flesh cells, chromoplasts could be observed only in LYQ during the middle and late stages of ripening, and the quantity on a per-cell basis was higher than that in peel cells, but the size of chromoplasts was smaller. It was concluded that chromoplasts are derived from the direct conversion of chloroplasts to chromoplasts in the peel, and from de novo differentiation of proplastids into chromoplasts in flesh. The relationship between plastid development and carotenoid accumulation is discussed.
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Kubik-Dobosz, Genowefa. "The activity of NADH-, NADPH- and Fd-dependent glutamate synthase in the plastids and cytosol of Pisum arvense L. root cells." Acta Societatis Botanicorum Poloniae 58, no. 2 (2014): 253–61. http://dx.doi.org/10.5586/asbp.1989.021.
Full textAbstract:
Three forms of glutamate synthase (NADH-GOGAT, NADPH-GOGAT and Fd-(ferredoxin) GOGAT) were found in the plastids and cytosol of <em>Pisum arvense </em>root cells. The activities of the enzymes of both fractions decreased with increasing age of the plants, with the exception of plastid NADPH-GOGAT which exhibited markedly stable activity. NADH-GOGAT dominated in the cytosol of root cells of several day-old plants but after 14 days of cultivation, the activities of all of the GOGAT forms equalized. Plastid NADH-GOGAT and Fd-GOGAT showed similar activities in the root cells of 3-5 day-old plants, with Fd-GOGAT becoming the dominant enzyme form after 14 days. The entire activity of NADH-GOGAT and Fd-GOGAT was confined to the plaslid stroma. The plastid membrane fraction contained 37% of the NADPH-GOGAT activity. Isolated plastids synthesized glutamate from 2-ketoglutarate and glutamine, and glucose-6-phosphate and 6-phosophogluconate clearly stimulated this process. It is supposed that the synthesis of glutamate in <em>Pisum arvense </em>root plastids may be dependent on the intensity of the carbohydrates conversion in the pentose phosphate pathway.
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Tchórzewska, D., V. B. Brukhin, and J. Bednara. "Plastids and mitochondria comportment in dividing meiocytes of Psilotum nudum." Acta Societatis Botanicorum Poloniae 65, no. 1-2 (2014): 91–96. http://dx.doi.org/10.5586/asbp.1996.016.
Full textAbstract:
In prophase I meiocyte plastids and mitochondria were situated at random. By telophase I plastids and mitochondria were aggregated in an equatorial plane. The aggregation was differentiated into three layers, the middle layer formed mostly by mitochondria, the outer layers consisted largely of plastids. By telophase II the mitochondria layers separated the cell into four domains, while plastid layers were disaggregated. Inside the mitochondrial layer the cell plates were formed. During this process mitochondria layers gradualy disintegrated. During prophase I to telophase I numerous plastids seem to undergo divisions. The telophase I layer mitochondria seemed to give rise to small electron-lucent vesicles.
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Martin, Thomas, and Frank Ludewig. "Transporters in starch synthesis." Functional Plant Biology 34, no. 6 (2007): 474. http://dx.doi.org/10.1071/fp06280.
Full textAbstract:
Starch is synthesised and stored in plastids. In autotrophic tissues, the carbon skeletons and energy required for starch synthesis are directly available from photosynthesis. However, plastids of heterotrophic tissues require the metabolites for starch synthesis to be imported. Depending on plant species and tissue type, import is facilitated by several different plastid inner envelope metabolite transporters. Commonly, glucose-6-phosphate/phosphate translocators and adenylate translocators are used, but in the cereal endosperm, the role is carried out by ADP glucose transporters (Brittle1, BT1). This review predominantly focuses on transporters of the plastid inner envelope membrane. Their roles are discussed within an overview of starch synthesis. We also examine additional functions of these transporters according to our current knowledge.
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Zhang, Yi, Kehan Sun, Francisco J. Sandoval, Katherine Santiago, and Sanja Roje. "One-carbon metabolism in plants: characterization of a plastid serine hydroxymethyltransferase." Biochemical Journal 430, no. 1 (July 28, 2010): 97–105. http://dx.doi.org/10.1042/bj20100566.
Full textAbstract:
SHMT (serine hydroxymethyltransferase; EC 2.1.2.1) catalyses reversible hydroxymethyl group transfer from serine to H4PteGlun (tetrahydrofolate), yielding glycine and 5,10-methylenetetrahydrofolate. In plastids, SHMTs are thought to catalytically direct the hydroxymethyl moiety of serine into the metabolic network of H4PteGlun-bound one-carbon units. Genes encoding putative plastid SHMTs were found in the genomes of various plant species. SHMT activity was detected in chloroplasts in pea (Pisum sativum) and barley (Hordeum vulgare), suggesting that plastid SHMTs exist in all flowering plants. The Arabidopsis thaliana genome encodes one putative plastid SHMT (AtSHMT3). Its cDNA was cloned by reverse transcription–PCR and the encoded recombinant protein was produced in Escherichia coli. Evidence that AtSHMT3 is targeted to plastids was found by confocal microscopy of A. thaliana protoplasts transformed with proteins fused to enhanced green fluorescent protein. Characterization of recombinant AtSHMT3 revealed that substrate affinity for and the catalytic efficiency of H4PteGlu1-8 increase with n, and that H4PteGlu1-8 inhibit AtSHMT3. 5-Methyltetrahydrofolate and 5-formyltetrahydrofolate with one and five glutamate residues inhibited AtSHMT3-catalysed hydroxymethyl group transfer from serine to H4PteGlu6, with the pentaglutamylated inhibitors being more effective. Calculations revealed inhibition with 5-methyltetrahydrofolate or 5-formyltetrahydrofolate resulting in little reduction in AtSHMT3 activity under folate concentrations estimated for plastids.
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Lukáčová, Alexandra, and Matej Vesteg. "Multiple Independent Losses of Photosynthetic Ability in Eukaryotic Evolution and the Metabolism of Non-Photosynthetic Plastids." Chemické listy 116, no. 5 (May 15, 2022): 316–23. http://dx.doi.org/10.54779/chl20220316.
Full textAbstract:
Multiple independent losses of photosynthesis have occurred among several unrelated eukaryotic lineages including red and green algae, land plants, alveolates, stramenopiles, cryptophytes and euglenophytes. Most plastid genomes of non-photosynthetic eukaryotes do not contain genes associated with photosynthesis, but they usually encode at least one gene product involved in an essential non-photosynthetic metabolic pathway. Complete loss of plastid genome and simultaneous retention of plastid compartment is rare, and complete plastid loss is documented only for few alveolate species. Non-photosynthetic plastids are often involved in essential fatty acid, isoprenoid, Fe-S cluster, and heme synthesis.
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Mikulska, Eugenia, Barbara Damasz, and Halina Żołnierowicz. "Structural and functional polymorphism of plastids in leaves of Clivia miniata Rgl. I. Ontogenesis of plastids in epidermis and guard cells." Acta Societatis Botanicorum Poloniae 50, no. 3 (2014): 381–89. http://dx.doi.org/10.5586/asbp.1981.060.
Full textAbstract:
During leaf ontogenesis in <em>Clivia miniata</em> epidermal and guard cell plastids differing in structure and function differentiate from morphologically equal proplastids. Plastid differentiation proceeds in parallel to cellular differentiation and stops in cells reaching maturity. It is suggested that the developmental sequence of plastids is fixed within cells and controlled by the inner mechanisms.
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Brunkard, Jacob O., and Tessa M. Burch-Smith. "Ties that bind: the integration of plastid signalling pathways in plant cell metabolism." Essays in Biochemistry 62, no. 1 (March 21, 2018): 95–107. http://dx.doi.org/10.1042/ebc20170011.
Full textAbstract:
Plastids are critical organelles in plant cells that perform diverse functions and are central to many metabolic pathways. Beyond their major roles in primary metabolism, of which their role in photosynthesis is perhaps best known, plastids contribute to the biosynthesis of phytohormones and other secondary metabolites, store critical biomolecules, and sense a range of environmental stresses. Accordingly, plastid-derived signals coordinate a host of physiological and developmental processes, often by emitting signalling molecules that regulate the expression of nuclear genes. Several excellent recent reviews have provided broad perspectives on plastid signalling pathways. In this review, we will highlight recent advances in our understanding of chloroplast signalling pathways. Our discussion focuses on new discoveries illuminating how chloroplasts determine life and death decisions in cells and on studies elucidating tetrapyrrole biosynthesis signal transduction networks. We will also examine the role of a plastid RNA helicase, ISE2, in chloroplast signalling, and scrutinize intriguing results investigating the potential role of stromules in conducting signals from the chloroplast to other cellular locations.
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BUSBY, C. H., and B. E. S. GUNNING. "Development of the Quadripolar Meiotic Cytoskeleton in Spore Mother Cells of the Moss Funaria Hygrometrica." Journal of Cell Science 91, no. 1 (September 1, 1988): 127–37. http://dx.doi.org/10.1242/jcs.91.1.127.
Full textAbstract:
Evidence presented in the accompanying paper that plastids function as microtubule (MT)-organizing centres for development of the quadripolar cytoskeleton of pre-meiotic spore mother cells (SMCs) in the moss Funaria hygrometrica is complemented here by observations on the MT system in these cells. Early in meiotic prophase numerous MTs align progressively along the two plastids as they elongate. Concomitant with (and perhaps causal for) plastid rotation, new MT arrays grow from each tip of each plastid to both tips of the other plastid. The ‘along-plastid’ and ‘between-plastid’ arrays ultimately form the edges of a tetrahedron, enclosing the prophase nucleus. MT breakdown at the centre of each edge leaves four cones of MTs, one emanating from each vertex, located at the plastid tips. These partially fuse in between-plastid pairs to give a twisted spindle with broad knife-edge poles oriented at right angles to one another, i.e. a condensed form of the quadripolar precursor. The twist causes the metaphase plate and the subsequent phragmoplast and organelle band to be saddle-shaped, and the daughter nuclei to be elongated perpendicular to one another along the two knife edges. The tetrahedral array returns during interkinesis and again breaks down into four cones of MTs centred on the plastid tips; these, however, now become individual half spindles for the two perpendicularly arranged second division spindles. When meiosis is completed the four haploid nuclei thus come to lie at the vertices of a tetrahedron that was established by MT-mediated plastid positioning during meiotic prophase. The tetrahedral cage of MTs precedes meiosis yet predicts the planes of division, and in these two respects it is the meiotic counterpart of the preprophase band of MTs, which develops before mitosis in most higher plant cells.
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Hertle, Alexander P., Benedikt Haberl, and Ralph Bock. "Horizontal genome transfer by cell-to-cell travel of whole organelles." Science Advances 7, no. 1 (January 2021): eabd8215. http://dx.doi.org/10.1126/sciadv.abd8215.
Full textAbstract:
Recent work has revealed that both plants and animals transfer genomes between cells. In plants, horizontal transfer of entire plastid, mitochondrial, or nuclear genomes between species generates new combinations of nuclear and organellar genomes, or produces novel species that are allopolyploid. The mechanisms of genome transfer between cells are unknown. Here, we used grafting to identify the mechanisms involved in plastid genome transfer from plant to plant. We show that during proliferation of wound-induced callus, plastids dedifferentiate into small, highly motile, amoeboid organelles. Simultaneously, new intercellular connections emerge by localized cell wall disintegration, forming connective pores through which amoeboid plastids move into neighboring cells. Our work uncovers a pathway of organelle movement from cell to cell and provides a mechanistic framework for horizontal genome transfer.
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Mellor, Silas Busck, James B. Y. H. Behrendorff, Agnieszka Zygadlo Nielsen, Poul Erik Jensen, and Mathias Pribil. "Non-photosynthetic plastids as hosts for metabolic engineering." Essays in Biochemistry 62, no. 1 (February 27, 2018): 41–50. http://dx.doi.org/10.1042/ebc20170047.
Full textAbstract:
Using plants as hosts for production of complex, high-value compounds and therapeutic proteins has gained increasing momentum over the past decade. Recent advances in metabolic engineering techniques using synthetic biology have set the stage for production yields to become economically attractive, but more refined design strategies are required to increase product yields without compromising development and growth of the host system. The ability of plant cells to differentiate into various tissues in combination with a high level of cellular compartmentalization represents so far the most unexploited plant-specific resource. Plant cells contain organelles called plastids that retain their own genome, harbour unique biosynthetic pathways and differentiate into distinct plastid types upon environmental and developmental cues. Chloroplasts, the plastid type hosting the photosynthetic processes in green tissues, have proven to be suitable for high yield protein and bio-compound production. Unfortunately, chloroplast manipulation often affects photosynthetic efficiency and therefore plant fitness. In this respect, plastids of non-photosynthetic tissues, which have focused metabolisms for synthesis and storage of particular classes of compounds, might prove more suitable for engineering the production and storage of non-native metabolites without affecting plant fitness. This review provides the current state of knowledge on the molecular mechanisms involved in plastid differentiation and focuses on non-photosynthetic plastids as alternative biotechnological platforms for metabolic engineering.