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Molina, Víctor Hugo, Raúl Eduardo Castillo-Medina e Patricia Elena Thomé. "Experimentally Induced Bleaching in the Sea Anemone Exaiptasia Supports Glucose as a Main Metabolite Associated with Its Symbiosis". Journal of Marine Biology 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/3130723.
Testo completoAbstract (sommario):
Our current understanding of carbon exchange between partners in the Symbiodinium-cnidarian symbioses is still limited, even though studies employing carbon isotopes have made us aware of the metabolic complexity of this exchange. We examined glycerol and glucose metabolism to better understand how photosynthates are exchanged between host and symbiont. The levels of these metabolites were compared between symbiotic and bleached Exaiptasia pallida anemones, assaying enzymes directly involved in their metabolism. We measured a significant decrease of glucose levels in bleached animals but a significant increase in glycerol and G3P pools, suggesting that bleached animals degrade lipids to compensate for the loss of symbionts and seem to rely on symbiotic glucose. The lower glycerol 3-phosphate dehydrogenase but higher glucose 6-phosphate dehydrogenase specific activities measured in bleached animals agree with a metabolic deficit mainly due to the loss of glucose from the ruptured symbiosis. These results corroborate previous observations on carbon translocation from symbiont to host in the sea anemone Exaiptasia, where glucose was proposed as a main translocated metabolite. To better understand photosynthate translocation and its regulation, additional research with other symbiotic cnidarians is needed, in particular, those with calcium carbonate skeletons.
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Marcinkowski, Andrzej. "Environmental Efficiency of Industrial Symbiosis – LCA Case Study for Gypsum Exchange". Multidisciplinary Aspects of Production Engineering 1, n. 1 (1 settembre 2018): 793–800. http://dx.doi.org/10.2478/mape-2018-0100.
Testo completoAbstract (sommario):
Abstract A review of the available literature concerning environmental impact assessment for industrial symbiosis has been carried out. The authors have recommended the use of life cycle assessment method for this purpose. It was stated that so far few studies presenting LCA results of industrial symbiosis have been published. Among the factors which contribute to the success of symbiotic exchange, the close location of collaborating companies has been often mentioned. This paper presents LCA results concerning the environmental impact of symbiotic gypsum transmission. Concepts of relative distance and critical distance for the case of industrial symbiosis were proposed and defined. Significant difference between critical distance obtained for particular endpoints were observed (3.5- 564 km). Application of Life Cycle Sustainability Triangle enabled the estimation of critical distance taking into account various impact categories. A sensitivity analysis indicated the relationship between critical distance and the means of transport which reflected the effect of scale. The critical distance determined for heavy trucks was 3.2 - 3.9 times longer than in case of lighter vehicles.
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Pringle, Elizabeth G., e Corrie S. Moreau. "Community analysis of microbial sharing and specialization in a Costa Rican ant–plant–hemipteran symbiosis". Proceedings of the Royal Society B: Biological Sciences 284, n. 1850 (15 marzo 2017): 20162770. http://dx.doi.org/10.1098/rspb.2016.2770.
Testo completoAbstract (sommario):
Ants have long been renowned for their intimate mutualisms with trophobionts and plants and more recently appreciated for their widespread and diverse interactions with microbes. An open question in symbiosis research is the extent to which environmental influence, including the exchange of microbes between interacting macroorganisms, affects the composition and function of symbiotic microbial communities. Here we approached this question by investigating symbiosis within symbiosis. Ant–plant–hemipteran symbioses are hallmarks of tropical ecosystems that produce persistent close contact among the macroorganism partners, which then have substantial opportunity to exchange symbiotic microbes. We used metabarcoding and quantitative PCR to examine community structure of both bacteria and fungi in a Neotropical ant–plant–scale-insect symbiosis. Both phloem-feeding scale insects and honeydew-feeding ants make use of microbial symbionts to subsist on phloem-derived diets of suboptimal nutritional quality. Among the insects examined here, Cephalotes ants and pseudococcid scale insects had the most specialized bacterial symbionts, whereas Azteca ants appeared to consume or associate with more fungi than bacteria, and coccid scale insects were associated with unusually diverse bacterial communities. Despite these differences, we also identified apparent sharing of microbes among the macro-partners. How microbial exchanges affect the consumer-resource interactions that shape the evolution of ant–plant–hemipteran symbioses is an exciting question that awaits further research.
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Khokhani, Devanshi, Cristobal Carrera Carriel, Shivangi Vayla, Thomas B. Irving, Christina Stonoha-Arther, Nancy P. Keller e Jean-Michel Ané. "Deciphering the Chitin Code in Plant Symbiosis, Defense, and Microbial Networks". Annual Review of Microbiology 75, n. 1 (8 ottobre 2021): 583–607. http://dx.doi.org/10.1146/annurev-micro-051921-114809.
Testo completoAbstract (sommario):
Chitin is a structural polymer in many eukaryotes. Many organisms can degrade chitin to defend against chitinous pathogens or use chitin oligomers as food. Beneficial microorganisms like nitrogen-fixing symbiotic rhizobia and mycorrhizal fungi produce chitin-based signal molecules called lipo-chitooligosaccharides (LCOs) and short chitin oligomers to initiate a symbiotic relationship with their compatible hosts and exchange nutrients. A recent study revealed that a broad range of fungi produce LCOs and chitooligosaccharides (COs), suggesting that these signaling molecules are not limited to beneficial microbes. The fungal LCOs also affect fungal growth and development, indicating that the roles of LCOs beyond symbiosis and LCO production may predate mycorrhizal symbiosis. This review describes the diverse structures of chitin; their perception by eukaryotes and prokaryotes; and their roles in symbiotic interactions, defense, and microbe-microbe interactions. We also discuss potential strategies of fungi to synthesize LCOs and their roles in fungi with different lifestyles.
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Sun, S., e G. Xu. "Sugar transport in arbuscular mycorrhizal symbiosis". Canadian Journal of Plant Science 89, n. 2 (1 marzo 2009): 257–63. http://dx.doi.org/10.4141/cjps07106.
Testo completoAbstract (sommario):
In arbuscular mycorrhizal (AM) symbioses, there is a reciprocal nutrient exchange, mainly sugar and phosphate, between partners. Transport of phosphate from fungus to plant has been well characterized, and this aspect of AM symbiosis has been reviewed. This mini-review is specifically devoted to sugar transport from plant to fungus in AM symbiosis and discusses the possible links between sugar transporters and AM-inducible inorganic phosphate (Pi) transporters and plasma membrane proton-ATPases in the arbuscule-cortical cell interface. Exploring the sugar transport mechanisms could further contribute to our understanding of nutrient exchange between the two symbiotic partners. Key words: Arbuscular mycorrhizal symbiosis, sugar flux, sugar transporter, phosphate transporter, plasma membrane, H+-ATPase
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Ovtsyna, Aleksandra O., e Igor A. Tikhonovich. "Structure, functions and perspectives of practical application of the signal molecules inducing development of rhizobia-legume symbiosis". Ecological genetics 2, n. 3 (15 settembre 2004): 14–24. http://dx.doi.org/10.17816/ecogen2314-24.
Testo completoAbstract (sommario):
Soil bacteria rhizobia establish nitrogen-fixing symbiosis with legume plants. Mutual recognition of symbiotic partners and initiation of nodule formation occur via exchange by molecular signals secreted both by plant and bacteria. This review summarizes recent data about structural diversity, genetic control of biosynthesis and functional role of Nod-factors. The possibilities of practical application of flavonoids and Nod-factors in agriculture are discussed
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Amalric, C., H. Sallanon, F. Monnet, A. Hitmi e A. Coudret. "Gas Exchange and Chlorophyll Fluorescence in Symbiotic and Non-Symbiotic Ryegrass Under Water Stress". Photosynthetica 37, n. 1 (1 luglio 1999): 107–12. http://dx.doi.org/10.1023/a:1007027131613.
Testo completo
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Liu, Sida. "Lawyers, State Officials and Significant Others: Symbiotic Exchange in the Chinese Legal Services Market". China Quarterly 206 (giugno 2011): 276–93. http://dx.doi.org/10.1017/s0305741011000269.
Testo completoAbstract (sommario):
AbstractIn China's legal services market, lawyers face strong competition from a variety of alternative legal service providers. Based upon 256 interviews with law practitioners and public officials, three years of ethnographic work on a professional internet forum, and extensive archival research, this article develops a theory of symbiotic exchange to analyse the competition between lawyers, basic-level legal workers and other practitioners in ordinary legal work, as well as how the state regulates these competing occupational groups. It argues that the dynamics of professional competition in the Chinese legal services market can be explained by the symbiotic exchange between law practitioners in the market and their regulatory agencies and officials in the state. Chinese lawyers have a weak market position because their exchange with the state is often not as strong and stable as their competitors. The prevalence of symbiotic exchange leads to the structural isomorphism between market and state institutions in China's transitional economy.
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Hinkle, Kenneth H., Francis C. Fekel, Richard Joyce, Thomas Lebzelter e Oscar Straniero. "Masses of white dwarfs in symbiotic binaries". Proceedings of the International Astronomical Union 15, S357 (ottobre 2019): 211–14. http://dx.doi.org/10.1017/s174392132000068x.
Testo completoAbstract (sommario):
AbstractMasses have been computed for the white dwarfs (WDs) in eclipsing, mass exchange (symbiotic), WD–red giant (RG) binaries by using single-lined spectroscopic orbits, orbital inclinations, and the RG masses. Inclinations have been measured for 13 eclipsing symbiotic binaries. Using Gaia data the mass of the RG can be found from evolutionary tracks. Since the WD evolved from the more massive star in the binary, the WD should be more massive than predicted from the mass of the current RG. Typically the WD has a lower mass than expected implying a previous mass exchange stage for these systems.
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Yurgel, Svetlana N., Jennifer Rice, Monika Mulder e Michael L. Kahn. "GlnB/GlnK PII Proteins and Regulation of the Sinorhizobium meliloti Rm1021 Nitrogen Stress Response and Symbiotic Function". Journal of Bacteriology 192, n. 10 (19 marzo 2010): 2473–81. http://dx.doi.org/10.1128/jb.01657-09.
Testo completoAbstract (sommario):
ABSTRACT The Sinorhizobium meliloti Rm1021ΔglnD-sm2 mutant, which is predicted to make a GlnD nitrogen sensor protein truncated at its amino terminus, fixes nitrogen in symbiosis with alfalfa, but the plants cannot use this nitrogen for growth (S. N. Yurgel and M. L. Kahn, Proc. Natl. Acad. Sci. U. S. A. 105:18958-18963, 2008). The mutant also has a generalized nitrogen stress response (NSR) defect. These results suggest a connection between GlnD, symbiotic metabolism, and the NSR, but the nature of this connection is unknown. In many bacteria, GlnD modifies the PII proteins, GlnB and GlnK, as it transduces a measurement of bacterial nitrogen status to a cellular response. We have now constructed and analyzed Rm1021 mutants missing GlnB, GlnK, or both proteins. Rm1021ΔglnKΔglnB was much more defective in its NSR than either single mutant, suggesting that GlnB and GlnK overlap in regulating the NSR in free-living Rm1021. The single mutants and the double mutant all formed an effective symbiosis, indicating that symbiotic nitrogen exchange could occur without the need for either GlnB or GlnK. N-terminal truncation of the GlnD protein interfered with PII protein modification in vitro, suggesting either that unmodified PII proteins were responsible for the glnD mutant's ineffective phenotype or that connecting GlnD and appropriate symbiotic behavior does not require the PII proteins.
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Dolgikh, Elena A., Irina V. Leppyanen, Maria A. Osipova e Igor A. Tikhonovich. "ROLE OF SIGNAL EXCHANGE IN CONTROL OF RHIZOBIUM - LEGUME SYMBIOSIS SPECIFICITY". Ecological genetics 6, n. 2 (15 giugno 2008): 27–34. http://dx.doi.org/10.17816/ecogen6227-34.
Testo completoAbstract (sommario):
The signal molecules produced by legume plants and soil bacteria rhizobia and involved in early steps of symbiosis regulation were identified through the evaluation of molecular mechanisms of plant-rhizobia communication. The molecular dialog between plants and rhizobia is initiated by plant flavanoids inducing the synthesis and secretion of lipochitooligosaccharide molecules Nod factors by rhizobial bacteria. Nod factors are N-acetylglucosamine oligomers, modified by fatty acid and certain chemical groups. Nod factors trigger a set of plant reactions resulting in a formation of root nodules - nitrogen fixing symbiotic organs. Fine chemical structure of signal molecules determines host specificity of the symbiosis. Nod factors are active in low concentrations and possess mitogenic and morphogenic activity, therefore they are recognized as the new class of growth regulators. In this paper the modern data about study of Nod factor perception mechanisms and signal transduction pathway in legume plants are presented and considered with perspective for future application of these knowledge for practical increasing of symbiosis efficiency from plant side. This work was supported by RFBR 07-08-00700a (Russian Foundation of Basic Research), CRDF RUXO-012-ST-06 (BP2M12) and HIII-5399. 2008. 4, RFBR-NWO (06-04-89000-НВОЦ-а) grants.
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Uchiumi, Yu, e Akira Sasaki. "Evolution of division of labour in mutualistic symbiosis". Proceedings of the Royal Society B: Biological Sciences 287, n. 1930 (8 luglio 2020): 20200669. http://dx.doi.org/10.1098/rspb.2020.0669.
Testo completoAbstract (sommario):
Mutualistic symbiosis can be regarded as interspecific division of labour, which can improve the productivity of metabolites and services but deteriorate the ability to live without partners. Interestingly, even in environmentally acquired symbiosis, involved species often rely exclusively on the partners despite the lethal risk of missing partners. To examine this paradoxical evolution, we explored the coevolutionary dynamics in symbiotic species for the amount of investment in producing their essential metabolites, which symbiotic species can share. Our study has shown that, even if obtaining partners is difficult, ‘perfect division of labour’ (PDL) can be maintained evolutionarily, where each species perfectly specializes in producing one of the essential metabolites so that every member entirely depends on the others for survival, i.e. in exchange for losing the ability of living alone. Moreover, the coevolutionary dynamics shows multistability with other states including a state without any specialization. It can cause evolutionary hysteresis: once PDL has been achieved evolutionarily when obtaining partners was relatively easy, it is not reverted even if obtaining partners becomes difficult later. Our study suggests that obligate mutualism with a high degree of mutual specialization can evolve and be maintained easier than previously thought.
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Alloisio, Nicole, Clothilde Queiroux, Pascale Fournier, Petar Pujic, Philippe Normand, David Vallenet, Claudine Médigue, Masatoshi Yamaura, Kentaro Kakoi e Ken-ichi Kucho. "The Frankia alni Symbiotic Transcriptome". Molecular Plant-Microbe Interactions® 23, n. 5 (maggio 2010): 593–607. http://dx.doi.org/10.1094/mpmi-23-5-0593.
Testo completoAbstract (sommario):
The actinobacteria Frankia spp. are able to induce the formation of nodules on the roots of a large spectrum of actinorhizal plants, where they convert dinitrogen to ammonia in exchange for plant photosynthates. In the present study, transcriptional analyses were performed on nitrogen-replete free-living Frankia alni cells and on Alnus glutinosa nodule bacteria, using whole-genome microarrays. Distribution of nodule-induced genes on the genome was found to be mostly over regions with high synteny between three Frankia spp. genomes, while nodule-repressed genes, which were mostly hypothetical and not conserved, were spread around the genome. Genes known to be related to nitrogen fixation were highly induced, nif (nitrogenase), hup2 (hydrogenase uptake), suf (sulfur-iron cluster), and shc (hopanoids synthesis). The expression of genes involved in ammonium assimilation and transport was strongly modified, suggesting that bacteria ammonium assimilation was limited. Genes involved in particular in transcriptional regulation, signaling processes, protein drug export, protein secretion, lipopolysaccharide, and peptidoglycan biosynthesis that may play a role in symbiosis were also identified. We also showed that this Frankia symbiotic transcriptome was highly similar among phylogenetically distant plant families Betulaceae and Myricaceae. Finally, comparison with rhizobia transcriptome suggested that F. alni is metabolically more active in symbiosis than rhizobia.
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Delaux, Pierre-Marc, Guru V. Radhakrishnan, Dhileepkumar Jayaraman, Jitender Cheema, Mathilde Malbreil, Jeremy D. Volkening, Hiroyuki Sekimoto et al. "Algal ancestor of land plants was preadapted for symbiosis". Proceedings of the National Academy of Sciences 112, n. 43 (5 ottobre 2015): 13390–95. http://dx.doi.org/10.1073/pnas.1515426112.
Testo completoAbstract (sommario):
Colonization of land by plants was a major transition on Earth, but the developmental and genetic innovations required for this transition remain unknown. Physiological studies and the fossil record strongly suggest that the ability of the first land plants to form symbiotic associations with beneficial fungi was one of these critical innovations. In angiosperms, genes required for the perception and transduction of diffusible fungal signals for root colonization and for nutrient exchange have been characterized. However, the origin of these genes and their potential correlation with land colonization remain elusive. A comprehensive phylogenetic analysis of 259 transcriptomes and 10 green algal and basal land plant genomes, coupled with the characterization of the evolutionary path leading to the appearance of a key regulator, a calcium- and calmodulin-dependent protein kinase, showed that the symbiotic signaling pathway predated the first land plants. In contrast, downstream genes required for root colonization and their specific expression pattern probably appeared subsequent to the colonization of land. We conclude that the most recent common ancestor of extant land plants and green algae was preadapted for symbiotic associations. Subsequent improvement of this precursor stage in early land plants through rounds of gene duplication led to the acquisition of additional pathways and the ability to form a fully functional arbuscular mycorrhizal symbiosis.
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Horváth, Beatrix, Li Huey Yeun, Ágota Domonkos, Gábor Halász, Enrico Gobbato, Ferhan Ayaydin, Krisztina Miró et al. "Medicago truncatula IPD3 Is a Member of the Common Symbiotic Signaling Pathway Required for Rhizobial and Mycorrhizal Symbioses". Molecular Plant-Microbe Interactions® 24, n. 11 (novembre 2011): 1345–58. http://dx.doi.org/10.1094/mpmi-01-11-0015.
Testo completoAbstract (sommario):
Legumes form endosymbiotic associations with nitrogen-fixing bacteria and arbuscular mycorrhizal (AM) fungi which facilitate nutrient uptake. Both symbiotic interactions require a molecular signal exchange between the plant and the symbiont, and this involves a conserved symbiosis (Sym) signaling pathway. In order to identify plant genes required for intracellular accommodation of nitrogen-fixing bacteria and AM fungi, we characterized Medicago truncatula symbiotic mutants defective for rhizobial infection of nodule cells and colonization of root cells by AM hyphae. Here, we describe mutants impaired in the interacting protein of DMI3 (IPD3) gene, which has been identified earlier as an interacting partner of the calcium/calmodulin-dependent protein, a member of the Sym pathway. The ipd3 mutants are impaired in both rhizobial and mycorrhizal colonization and we show that IPD3 is necessary for appropriate Nod-factor-induced gene expression. This indicates that IPD3 is a member of the common Sym pathway. We observed differences in the severity of ipd3 mutants that appear to be the result of the genetic background. This supports the hypothesis that IPD3 function is partially redundant and, thus, additional genetic components must exist that have analogous functions to IPD3. This explains why mutations in an essential component of the Sym pathway have defects at late stages of the symbiotic interactions.
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Mills, Benjamin J. W., Sarah A. Batterman e Katie J. Field. "Nutrient acquisition by symbiotic fungi governs Palaeozoic climate transition". Philosophical Transactions of the Royal Society B: Biological Sciences 373, n. 1739 (18 dicembre 2017): 20160503. http://dx.doi.org/10.1098/rstb.2016.0503.
Testo completoAbstract (sommario):
Fossil evidence from the Rhynie chert indicates that early land plants, which evolved in a high-CO 2 atmosphere during the Palaeozoic Era, hosted diverse fungal symbionts. It is hypothesized that the rise of early non-vascular land plants, and the later evolution of roots and vasculature, drove the long-term shift towards a high-oxygen, low CO 2 climate that eventually permitted the evolution of mammals and, ultimately, humans. However, very little is known about the productivity of the early terrestrial biosphere, which depended on the acquisition of the limiting nutrient phosphorus via fungal symbiosis. Recent laboratory experiments have shown that plant–fungal symbiotic function is specific to fungal identity, with carbon-for-phosphorus exchange being either enhanced or suppressed under superambient CO 2 . By incorporating these experimental findings into a biogeochemical model, we show that the differences in these symbiotic nutrient acquisition strategies could greatly alter the plant-driven changes to climate, allowing drawdown of CO 2 to glacial levels, and altering the nature of the rise of oxygen. We conclude that an accurate depiction of plant–fungal symbiotic systems, informed by high-CO 2 experiments, is key to resolving the question of how the first terrestrial ecosystems altered our planet. This article is part of a discussion meeting issue ‘The Rhynie cherts: our earliest terrestrial ecosystem revisited’.
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Liu, Zhilei, Yuanjing Li, Lina Ma, Haichao Wei, Jianfeng Zhang, Xingyuan He e Chunjie Tian. "Coordinated Regulation of Arbuscular Mycorrhizal Fungi and Soybean MAPK Pathway Genes Improved Mycorrhizal Soybean Drought Tolerance". Molecular Plant-Microbe Interactions® 28, n. 4 (aprile 2015): 408–19. http://dx.doi.org/10.1094/mpmi-09-14-0251-r.
Testo completoAbstract (sommario):
Mitogen-activated protein kinase (MAPK) cascades play important roles in the stress response in both plants and microorganisms. The mycorrhizal symbiosis established between arbuscular mycorrhizal fungi (AMF) and plants can enhance plant drought tolerance, which might be closely related to the fungal MAPK response and the molecular dialogue between fungal and soybean MAPK cascades. To verify the above hypothesis, germinal Glomus intraradices (syn. Rhizophagus irregularis) spores and potted experiments were conducted. The results showed that AMF GiMAPKs with high homology with MAPKs from Saccharomyces cerevisiae had different gene expression patterns under different conditions (nitrogen starvation, abscisic acid treatment, and drought). Drought stress upregulated the levels of fungi and soybean MAPK transcripts in mycorrhizal soybean roots, indicating the possibility of a molecular dialogue between the two symbiotic sides of symbiosis and suggesting that they might cooperate to regulate the mycorrhizal soybean drought-stress response. Meanwhile, the changes in hydrogen peroxide, soluble sugar, and proline levels in mycorrhizal soybean as well as in the accelerated exchange of carbon and nitrogen in the symbionts were contributable to drought adaptation of the host plants. Thus, it can be preliminarily inferred that the interactions of MAPK signals on both sides, symbiotic fungus and plant, might regulate the response of symbiosis and, thus, improve the resistance of mycorrhizal soybean to drought stress.
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Lorkiewicz, Z. "Nodulation genes in the Rhizobium--plant signal exchange." Acta Biochimica Polonica 44, n. 1 (31 marzo 1997): 1–12. http://dx.doi.org/10.18388/abp.1997_4434.
Testo completoAbstract (sommario):
The process of the host-plant recognition by rhizobia is complex and multi-step. The interaction between legumes and microorganisms results in the induction of the root nodule. This symbiotic interaction is highly host-specific. Bacteria within nodules fix atmospheric nitrogen. This process is of immense ecological and economic significance. The subject of this presentation is the molecular mechanism by which the bacterium determines its host-specific characteristics. First flavonoids secreted by the plant roots induce the transcription of bacterial genes involved in nodulation, the so-called nod genes. This leads to the next step of the signalling system, i.e. the production and secretion of lipo-oligosaccharide molecules by rhizobia. These signal molecules have various discernible effects on the roots of the host leguminous plants. The bacterial nodulation factors were isolated and structurally identified as substituted and N-acylated chitin oligosaccharides. These prokaryotic signals play a key role in the symbiosis by controlling the host specificity of the bacteria. They constitute a new class of signalling molecules able to elicit nodule organogenesis in leguminous plants in the absence of bacteria. More recent studies implicate involvement of root cell membrane depolarization and ion selective channels in the communication processes that initiate nodule formation.
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Colard, Alexandre, Caroline Angelard e Ian R. Sanders. "Genetic Exchange in an Arbuscular Mycorrhizal Fungus Results in Increased Rice Growth and Altered Mycorrhiza-Specific Gene Transcription". Applied and Environmental Microbiology 77, n. 18 (22 luglio 2011): 6510–15. http://dx.doi.org/10.1128/aem.05696-11.
Testo completoAbstract (sommario):
ABSTRACTArbuscular mycorrhizal fungi (AMF) are obligate symbionts with most terrestrial plants. They improve plant nutrition, particularly phosphate acquisition, and thus are able to improve plant growth. In exchange, the fungi obtain photosynthetically fixed carbon. AMF are coenocytic, meaning that many nuclei coexist in a common cytoplasm. Genetic exchange recently has been demonstrated in the AMFGlomus intraradices, allowing nuclei of differentGlomus intraradicesstrains to mix. Such genetic exchange was shown previously to have negative effects on plant growth and to alter fungal colonization. However, no attempt was made to detect whether genetic exchange in AMF can alter plant gene expression and if this effect was time dependent. Here, we show that genetic exchange in AMF also can be beneficial for rice growth, and that symbiosis-specific gene transcription is altered by genetic exchange. Moreover, our results show that genetic exchange can change the dynamics of the colonization of the fungus in the plant. Our results demonstrate that the simple manipulation of the genetics of AMF can have important consequences for their symbiotic effects on plants such as rice, which is considered the most important crop in the world. Exploiting natural AMF genetic variation by generating novel AMF genotypes through genetic exchange is a potentially useful tool in the development of AMF inocula that are more beneficial for crop growth.
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ten Veldhuis, Marie-Claire, Gennady Ananyev e G. Charles Dismukes. "Symbiosis extended: exchange of photosynthetic O2 and fungal-respired CO2 mutually power metabolism of lichen symbionts". Photosynthesis Research 143, n. 3 (31 dicembre 2019): 287–99. http://dx.doi.org/10.1007/s11120-019-00702-0.
Testo completoAbstract (sommario):
AbstractLichens are a symbiosis between a fungus and one or more photosynthetic microorganisms that enables the symbionts to thrive in places and conditions they could not compete independently. Exchanges of water and sugars between the symbionts are the established mechanisms that support lichen symbiosis. Herein, we present a new linkage between algal photosynthesis and fungal respiration in lichen Flavoparmelia caperata that extends the physiological nature of symbiotic co-dependent metabolisms, mutually boosting energy conversion rates in both symbionts. Measurements of electron transport by oximetry show that photosynthetic O2 is consumed internally by fungal respiration. At low light intensity, very low levels of O2 are released, while photosynthetic electron transport from water oxidation is normal as shown by intrinsic chlorophyll variable fluorescence yield (period-4 oscillations in flash-induced Fv/Fm). The rate of algal O2 production increases following consecutive series of illumination periods, at low and with limited saturation at high light intensities, in contrast to light saturation in free-living algae. We attribute this effect to arise from the availability of more CO2 produced by fungal respiration of photosynthetically generated sugars. We conclude that the lichen symbionts are metabolically coupled by energy conversion through exchange of terminal electron donors and acceptors used in both photosynthesis and fungal respiration. Algal sugars and O2 are consumed by the fungal symbiont, while fungal delivered CO2 is consumed by the alga.
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Xue, Li, Lompong Klinnawee, Yue Zhou, Georgios Saridis, Vinod Vijayakumar, Mathias Brands, Peter Dörmann, Tamara Gigolashvili, Franziska Turck e Marcel Bucher. "AP2 transcription factor CBX1 with a specific function in symbiotic exchange of nutrients in mycorrhizal Lotus japonicus". Proceedings of the National Academy of Sciences 115, n. 39 (12 settembre 2018): E9239—E9246. http://dx.doi.org/10.1073/pnas.1812275115.
Testo completoAbstract (sommario):
The arbuscular mycorrhizal (AM) symbiosis, a widespread mutualistic association between land plants and fungi, depends on reciprocal exchange of phosphorus driven by proton-coupled phosphate uptake into host plants and carbon supplied to AM fungi by host-dependent sugar and lipid biosynthesis. The molecular mechanisms and cis-regulatory modules underlying the control of phosphate uptake and de novo fatty acid synthesis in AM symbiosis are poorly understood. Here, we show that the AP2 family transcription factor CTTC MOTIF-BINDING TRANSCRIPTION FACTOR1 (CBX1), a WRINKLED1 (WRI1) homolog, directly binds the evolutionary conserved CTTC motif that is enriched in mycorrhiza-regulated genes and activates Lotus japonicus phosphate transporter 4 (LjPT4) in vivo and in vitro. Moreover, the mycorrhiza-inducible gene encoding H+-ATPase (LjHA1), implicated in energizing nutrient uptake at the symbiotic interface across the periarbuscular membrane, is coregulated with LjPT4 by CBX1. Accordingly, CBX1-defective mutants show reduced mycorrhizal colonization. Furthermore, genome-wide–binding profiles, DNA-binding studies, and heterologous expression reveal additional binding of CBX1 to AW box, the consensus DNA-binding motif for WRI1, that is enriched in promoters of glycolysis and fatty acid biosynthesis genes. We show that CBX1 activates expression of lipid metabolic genes including glycerol-3-phosphate acyltransferase RAM2 implicated in acylglycerol biosynthesis. Our finding defines the role of CBX1 as a regulator of host genes involved in phosphate uptake and lipid synthesis through binding to the CTTC/AW molecular module, and supports a model underlying bidirectional exchange of phosphorus and carbon, a fundamental trait in the mutualistic AM symbiosis.
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Berry, Alison M., Alberto Mendoza-Herrera, Ying-Yi Guo, Jennifer Hayashi, Tomas Persson, Ravi Barabote, Kirill Demchenko, Shuxiao Zhang e Katharina Pawlowski. "New perspectives on nodule nitrogen assimilation in actinorhizal symbioses". Functional Plant Biology 38, n. 9 (2011): 645. http://dx.doi.org/10.1071/fp11095.
Testo completoAbstract (sommario):
Nitrogen-fixing root nodules are plant organs specialised for symbiotic transfer of nitrogen and carbon between microsymbiont and host. The organisation of nitrogen assimilation, storage and transport processes is partitioned at the subcellular and tissue levels, in distinctive patterns depending on the symbiotic partners. In this review, recent advances in understanding of actinorhizal nodule nitrogen assimilation are presented. New findings indicate that Frankia within nodules of Datisca glomerata (Presl.) Baill. carries out both primary nitrogen assimilation and biosynthesis of arginine, rather than exporting ammonium. Arginine is a typical storage form of nitrogen in plant tissues, but is a novel nitrogen carrier molecule in root nodule symbioses. Thus Frankia within D. glomerata nodules exhibits considerable metabolic independence. Furthermore, nitrogen reassimilation is likely to take place in the host in the uninfected nodule cortical cells of this root nodule symbiosis, before amino acid export to host sink tissues via the xylem. The role of an augmented pericycle in carbon and nitrogen exchange in root nodules deserves further attention in actinorhizal symbiosis, and further highlights the importance of a comprehensive, structure–function approach to understanding function in root nodules. Moreover, the multiple patterns of compartmentalisation in relation to nitrogen flux within root nodules demonstrate the diversity of possible functional interactions between host and microsymbiont that have evolved in the nitrogen-fixing clade.
23
Provorov, Nikolay A., e Nikolay I. Vorobyov. "SIMULATION OF PLANT-BACTERIA CO-EVOLUTION IN THE MUTUALLY BENEFICIAL SYMBIOSIS". Ecological genetics 6, n. 2 (15 giugno 2008): 35–48. http://dx.doi.org/10.17816/ecogen6235-48.
Testo completoAbstract (sommario):
The mathematical model for evolution of legume-rhizobia mutualism based on the partners' positive feedbacks resulted from their metabolic (C-N) exchange is presented. Negative FDS in rhizobia population, combined with the partners' positive feedbacks ensure anchoring or even domination of the mutants which either acquired the mutualistic traits or changed the specificity in their expression with different host genotypes. The created model allows us to consider the mutualistic symbiosis as of a finely balanced population system in which the equilibrium may be shifted in favor of beneficial microbial genotypes due to natural selection for an improved symbiotic efficiency implemented in plant population. Research is supported by RFBR grant 06-04-48800a.
24
Patriarca, Eduardo J., Rosarita Tatè e Maurizio Iaccarino. "Key Role of Bacterial NH4+ Metabolism in Rhizobium-Plant Symbiosis". Microbiology and Molecular Biology Reviews 66, n. 2 (giugno 2002): 203–22. http://dx.doi.org/10.1128/mmbr.66.2.203-222.2002.
Testo completoAbstract (sommario):
SUMMARY Symbiotic nitrogen fixation is carried out in specialized organs, the nodules, whose formation is induced on leguminous host plants by bacteria belonging to the family Rhizobiaceae. Nodule development is a complex multistep process, which requires continued interaction between the two partners and thus the exchange of different signals and metabolites. NH4 + is not only the primary product but also the main regulator of the symbiosis: either as ammonium and after conversion into organic compounds, it regulates most stages of the interaction, from the production of nodule inducers to the growth, function, and maintenance of nodules. This review examines the adaptation of bacterial NH4 + metabolism to the variable environment generated by the plant, which actively controls and restricts bacterial growth by affecting oxygen and nutrient availability, thereby allowing a proficient interaction and at the same time preventing parasitic invasion. We describe the regulatory circuitry responsible for the downregulation of bacterial genes involved in NH4 + assimilation occurring early during nodule invasion. This is a key and necessary step for the differentiation of N2-fixing bacteroids (the endocellular symbiotic form of rhizobia) and for the development of efficient nodules.
25
Libault, Marc, Manjula Govindarajulu, R. Howard Berg, Yee Tsuey Ong, Kari Puricelli, Christopher G. Taylor, Dong Xu e Gary Stacey. "A Dual-Targeted Soybean Protein Is Involved in Bradyrhizobium japonicum Infection of Soybean Root Hair and Cortical Cells". Molecular Plant-Microbe Interactions® 24, n. 9 (settembre 2011): 1051–60. http://dx.doi.org/10.1094/mpmi-12-10-0281.
Testo completoAbstract (sommario):
The symbiotic interaction between legumes and soil bacteria (e.g., soybean [Glycine max L.] and Bradyrhizobium japonicum]) leads to the development of a new root organ, the nodule, where bacteria differentiate into bacteroids that fix atmospheric nitrogen for assimilation by the plant host. In exchange, the host plant provides a steady carbon supply to the bacteroids. This carbon can be stored within the bacteroids in the form of poly-3-hydroxybutyrate granules. The formation of this symbiosis requires communication between both partners to regulate the balance between nitrogen fixation and carbon utilization. In the present study, we describe the soybean gene GmNMNa that is specifically expressed during the infection of soybean cells by B. japonicum. GmNMNa encodes a protein of unknown function. The GmNMNa protein was localized to the nucleolus and also to the mitochondria. Silencing of GmNMNa expression resulted in reduced nodulation, a reduction in the number of bacteroids per infected cell in the nodule, and a clear reduction in the accumulation of poly-3-hydroxybutyrate in the bacteroids. Our results highlight the role of the soybean GmNMNa gene in regulating symbiotic bacterial infection, potentially through the regulation of the accumulation of carbon reserves.
26
Yeh, Chuan-Ming, KwiMi Chung, Chieh-Kai Liang e Wen-Chieh Tsai. "New Insights into the Symbiotic Relationship between Orchids and Fungi". Applied Sciences 9, n. 3 (11 febbraio 2019): 585. http://dx.doi.org/10.3390/app9030585.
Testo completoAbstract (sommario):
Mycorrhizas play an important role in plant growth and development. In mycorrhizal symbioses, fungi supply soil mineral nutrients, such as nitrogen and phosphorus, to their host plants in exchange for carbon resources. Plants gain as much as 80% of mineral nutrient requirements from mycorrhizal fungi, which form associations with the roots of over 90% of all plant species. Orchid seeds lack endosperms and contain very limited storage reserves. Therefore, the symbiosis with mycorrhizal fungi that form endomycorrhizas is essential for orchid seed germination and protocorm development under natural conditions. The rapid advancement of next-generation sequencing contributes to identifying the orchid and fungal genes involved in the orchid mycorrhizal symbiosis and unraveling the molecular mechanisms regulating the symbiosis. We aim to update and summarize the current understanding of the mechanisms on orchid-fungus symbiosis, and the main focus will be on the nutrient exchange between orchids and their fungal partners.
27
Kryukov, A. A., A. O. Gorbunova, T. R. Kudriashova, O. I. Yakhin, A. A. Lubyanov, U. M. Malikov, M. F. Shishova, A. P. Kozhemyakov e A. P. Yurkov. "Sugar transporters of the SWEET family and their role in arbuscular mycorrhiza". Vavilov Journal of Genetics and Breeding 25, n. 7 (3 dicembre 2021): 754–60. http://dx.doi.org/10.18699/vj21.086.
Testo completoAbstract (sommario):
Plant sugar transporters play an essential role in the organism’s productivity by carrying out carbohydrate transportation from source cells in the leaves to sink cells in the cortex. In addition, they aid in the regulation of a substantial part of the exchange of nutrients with microorganisms in the rhizosphere (bacteria and fungi), an activity essential to the formation of symbiotic relationships. This review pays special attention to carbohydrate nutrition during the development of arbuscular mycorrhiza (AM), a symbiosis of plants with fungi from the Glomeromycotina subdivision. This relationship results in the host plant receiving micronutrients from the mycosymbiont, mainly phosphorus, and the fungus receiving carbon assimilation products in return. While the efficient nutrient transport pathways in AM symbiosis are yet to be discovered, SWEET sugar transporters are one of the three key families of plant carbohydrate transporters. Specific AM symbiosis transporters can be identified among the SWEET proteins. The survey provides data on the study history, structure and localization, phylogeny and functions of the SWEET proteins. A high variability of both the SWEET proteins themselves and their functions is noted along with the fact that the same proteins may perform different functions in different plants. A special role is given to the SWEET transporters in AM development. SWEET transporters can also play a key role in abiotic stress tolerance, thus allowing plants to adapt to adverse environmental conditions. The development of knowledge about symbiotic systems will contribute to the creation of microbial preparations for use in agriculture in the Russian Federation.
28
Rich, Mélanie K., Nicolas Vigneron, Cyril Libourel, Jean Keller, Li Xue, Mohsen Hajheidari, Guru V. Radhakrishnan et al. "Lipid exchanges drove the evolution of mutualism during plant terrestrialization". Science 372, n. 6544 (20 maggio 2021): 864–68. http://dx.doi.org/10.1126/science.abg0929.
Testo completoAbstract (sommario):
Symbiosis with arbuscular mycorrhizal fungi (AMF) improves plant nutrition in most land plants, and its contribution to the colonization of land by plants has been hypothesized. Here, we identify a conserved transcriptomic response to AMF among land plants, including the activation of lipid metabolism. Using gain of function, we show the transfer of lipids from the liverwort Marchantia paleacea to AMF and its direct regulation by the transcription factor WRINKLED (WRI). Arbuscules, the nutrient-exchange structures, were not formed in loss-of-function wri mutants in M. paleacea, leading to aborted mutualism. Our results show the orthology of the symbiotic transfer of lipids across land plants and demonstrate that mutualism with arbuscular mycorrhizal fungi was present in the most recent ancestor of land plants 450 million years ago.
29
Lockwood, Jane, e Ying Song. "Understanding Each Other: Strategies for Accommodation in a Virtual Business Team Project Based in China". International Journal of Business Communication 57, n. 1 (30 ottobre 2016): 113–44. http://dx.doi.org/10.1177/2329488416675841.
Testo completoAbstract (sommario):
The use of accommodation strategies between native and nonnative interlocutors of English in the rapidly increased virtual and global work contexts remains underresearched. Contextualized in a Chinese IT outsourcing company where English is used as a lingua franca, this study focuses on how accommodation strategies are used by both on- and offshore team project members in their virtual meeting exchanges. The article argues that the actual linguistic exchange appears to be scaffolded and facilitated by a series of what the authors call “extratextual accommodation strategies” such as the use of detailed minutes of tasks set and completed, and an agreed meeting format. While “intratextual accommodation strategies,” that is, those relating to specific linguistic behaviors in English in the exchanges are also used by interlocutors to accommodate to each other’s speech; the article argues, therefore, that both extra- and intratextual accommodation strategies appear to work in a symbiotic way to ensure successful exchange in business virtual meeting contexts.
30
Benjamin, Goodluck, Gaurav Pandharikar e Pierre Frendo. "Salicylic Acid in Plant Symbioses: Beyond Plant Pathogen Interactions". Biology 11, n. 6 (3 giugno 2022): 861. http://dx.doi.org/10.3390/biology11060861.
Testo completoAbstract (sommario):
Plants form beneficial symbioses with a wide variety of microorganisms. Among these, endophytes, arbuscular mycorrhizal fungi (AMF), and nitrogen-fixing rhizobia are some of the most studied and well understood symbiotic interactions. These symbiotic microorganisms promote plant nutrition and growth. In exchange, they receive the carbon and metabolites necessary for their development and multiplication. In addition to their role in plant growth and development, these microorganisms enhance host plant tolerance to a wide range of environmental stress. Multiple studies have shown that these microorganisms modulate the phytohormone metabolism in the host plant. Among the phytohormones involved in the plant defense response against biotic environment, salicylic acid (SA) plays an important role in activating plant defense. However, in addition to being a major actor in plant defense signaling against pathogens, SA has also been shown to be involved in plant–microbe symbiotic interactions. In this review, we summarize the impact of SA on the symbiotic interactions. In addition, we give an overview of the impact of the endophytes, AMF, and rhizobacteria on SA-mediated defense response against pathogens.
31
Zhang, Xue-Xian, Bob Kosier e Ursula B. Priefer. "Symbiotic Plasmid Rearrangement in Rhizobium leguminosarum bv. viciae VF39SM". Journal of Bacteriology 183, n. 6 (15 marzo 2001): 2141–44. http://dx.doi.org/10.1128/jb.183.6.2141-2144.2001.
Testo completoAbstract (sommario):
ABSTRACT A rearrangement between the symbiotic plasmid (pRleVF39d) and a nonsymbiotic plasmid (pRleVF39b) in Rhizobium leguminosarumbv. viciae VF39 was observed. The rearranged derivative showed the same plasmid profile as its parent strain, but hybridization to nod, fix, and nif genes indicated that most of the symbiotic genes were now present on a plasmid corresponding in size to pRleVF39b instead of pRleVF39d. On the other hand, some DNA fragments originating from pRleVF39b now hybridized to the plasmid band at the position of pRleVF39d. These results suggest that a reciprocal but unequal DNA exchange between the two plasmids had occurred.
32
Kwok, Sun. "Wind Accretion and Interaction in Long Period Binary Systems". Highlights of Astronomy 7 (1986): 189–95. http://dx.doi.org/10.1017/s1539299600006407.
Testo completoAbstract (sommario):
AbstractRecent observations of the class of objects called symbiotic nova are reviewed. They are suggested to be widely-separated long-period binary systems undergoing mass exchange by wind accretion. Their radio, infrared, optical and X-ray properties are explained by a model of interacting winds.
33
Mutalipassi, Mirko, Gennaro Riccio, Valerio Mazzella, Christian Galasso, Emanuele Somma, Antonia Chiarore, Donatella de Pascale e Valerio Zupo. "Symbioses of Cyanobacteria in Marine Environments: Ecological Insights and Biotechnological Perspectives". Marine Drugs 19, n. 4 (16 aprile 2021): 227. http://dx.doi.org/10.3390/md19040227.
Testo completoAbstract (sommario):
Cyanobacteria are a diversified phylum of nitrogen-fixing, photo-oxygenic bacteria able to colonize a wide array of environments. In addition to their fundamental role as diazotrophs, they produce a plethora of bioactive molecules, often as secondary metabolites, exhibiting various biological and ecological functions to be further investigated. Among all the identified species, cyanobacteria are capable to embrace symbiotic relationships in marine environments with organisms such as protozoans, macroalgae, seagrasses, and sponges, up to ascidians and other invertebrates. These symbioses have been demonstrated to dramatically change the cyanobacteria physiology, inducing the production of usually unexpressed bioactive molecules. Indeed, metabolic changes in cyanobacteria engaged in a symbiotic relationship are triggered by an exchange of infochemicals and activate silenced pathways. Drug discovery studies demonstrated that those molecules have interesting biotechnological perspectives. In this review, we explore the cyanobacterial symbioses in marine environments, considering them not only as diazotrophs but taking into consideration exchanges of infochemicals as well and emphasizing both the chemical ecology of relationship and the candidate biotechnological value for pharmaceutical and nutraceutical applications.
34
Yamagishi, Jumpei F., Nen Saito e Kunihiko Kaneko. "Adaptation of metabolite leakiness leads to symbiotic chemical exchange and to a resilient microbial ecosystem". PLOS Computational Biology 17, n. 6 (23 giugno 2021): e1009143. http://dx.doi.org/10.1371/journal.pcbi.1009143.
Testo completoAbstract (sommario):
Microbial communities display remarkable diversity, facilitated by the secretion of chemicals that can create new niches. However, it is unclear why cells often secrete even essential metabolites after evolution. Based on theoretical results indicating that cells can enhance their own growth rate by leaking even essential metabolites, we show that such “leaker” cells can establish an asymmetric form of mutualism with “consumer” cells that consume the leaked chemicals: the consumer cells benefit from the uptake of the secreted metabolites, while the leaker cells also benefit from such consumption, as it reduces the metabolite accumulation in the environment and thereby enables further secretion, resulting in frequency-dependent coexistence of multiple microbial species. As supported by extensive simulations, such symbiotic relationships generally evolve when each species has a complex reaction network and adapts its leakiness to optimize its own growth rate under crowded conditions and nutrient limitations. Accordingly, symbiotic ecosystems with diverse cell species that leak and exchange many metabolites with each other are shaped by cell-level adaptation of leakiness of metabolites. Moreover, the resultant ecosystems with entangled metabolite exchange are resilient against structural and environmental perturbations. Thus, we present a theory for the origin of resilient ecosystems with diverse microbes mediated by secretion and exchange of essential chemicals.
35
Kameoka, Hiromu, Taro Maeda, Nao Okuma e Masayoshi Kawaguchi. "Structure-Specific Regulation of Nutrient Transport and Metabolism in Arbuscular Mycorrhizal Fungi". Plant and Cell Physiology 60, n. 10 (26 giugno 2019): 2272–81. http://dx.doi.org/10.1093/pcp/pcz122.
Testo completoAbstract (sommario):
Abstract Arbuscular mycorrhizal fungi (AMF) establish symbiotic relationships with most land plants, mainly for the purpose of nutrient exchange. Many studies have revealed the regulation of processes in AMF, such as nutrient absorption from soil, metabolism and exchange with host plants, and the genes involved. However, the spatial regulation of the genes within the structures comprising each developmental stage is not well understood. Here, we demonstrate the structure-specific transcriptome of the model AMF species, Rhizophagus irregularis. We performed an ultra-low input RNA-seq analysis, SMART-seq2, comparing five extraradical structures, germ tubes, runner hyphae, branched absorbing structures (BAS), immature spores and mature spores. In addition, we reanalyzed the recently reported RNA-seq data comparing intraradical mycelium and arbuscule. Our analyses captured the distinct features of each structure and revealed the structure-specific expression patterns of genes related to nutrient transport and metabolism. Of note, the transcriptional profiles suggest distinct functions of BAS in nutrient absorption. These findings provide a comprehensive dataset to advance our understanding of the transcriptional dynamics of fungal nutrition in this symbiotic system.
36
LeKieffre, Charlotte, Howard J. Spero, Jennifer S. Fehrenbacher, Ann D. Russell, Haojia Ren, Emmanuelle Geslin e Anders Meibom. "Ammonium is the preferred source of nitrogen for planktonic foraminifer and their dinoflagellate symbionts". Proceedings of the Royal Society B: Biological Sciences 287, n. 1929 (17 giugno 2020): 20200620. http://dx.doi.org/10.1098/rspb.2020.0620.
Testo completoAbstract (sommario):
The symbiotic planktonic foraminifera Orbulina universa inhabits open ocean oligotrophic ecosystems where dissolved nutrients are scarce and often limit biological productivity. It has previously been proposed that O. universa meets its nitrogen (N) requirements by preying on zooplankton, and that its symbiotic dinoflagellates recycle metabolic ‘waste ammonium’ for their N pool. However, these conclusions were derived from bulk 15 N-enrichment experiments and model calculations, and our understanding of N assimilation and exchange between the foraminifer host cell and its symbiotic dinoflagellates remains poorly constrained. Here, we present data from pulse-chase experiments with 13 C-enriched inorganic carbon, 15 N-nitrate, and 15 N-ammonium, as well as a 13 C- and 15 N- enriched heterotrophic food source, followed by TEM (transmission electron microscopy) coupled to NanoSIMS (nanoscale secondary ion mass spectrometry) isotopic imaging to visualize and quantify C and N assimilation and translocation in the symbiotic system. High levels of 15 N-labelling were observed in the dinoflagellates and in foraminiferal organelles and cytoplasm after incubation with 15 N-ammonium, indicating efficient ammonium assimilation. Only weak 15 N-assimilation was observed after incubation with 15 N-nitrate. Feeding foraminifers with 13 C- and 15 N-labelled food resulted in dinoflagellates that were labelled with 15 N, thereby confirming the transfer of 15 N-compounds from the digestive vacuoles of the foraminifer to the symbiotic dinoflagellates, likely through recycling of ammonium. These observations are important for N isotope-based palaeoceanographic reconstructions, as they show that δ 15 N values recorded in the organic matrix in symbiotic species likely reflect ammonium recycling rather than alternative N sources, such as nitrates.
37
Corcoz, Larisa, Florin Păcurar, Victoria Pop-Moldovan, Ioana Vaida, Anca Pleșa, Vlad Stoian e Roxana Vidican. "Long-Term Fertilization Alters Mycorrhizal Colonization Strategy in the Roots of Agrostis capillaris". Agriculture 12, n. 6 (12 giugno 2022): 847. http://dx.doi.org/10.3390/agriculture12060847.
Testo completoAbstract (sommario):
Long-term fertilization targets mycorrhizal fungi adapted to symbiotic exchange of nutrients, thus restricting their colonization potential and re-orienting the colonization strategies. The MycoPatt tool has a high applicability in quantifying the symbiotic process with the identification of mycorrhizal indices and projection of mycorrhizal patterns. Organic treatments increase the symbiotic process, visible in values of colonization frequency and intensity, with about 6% more than the native status of colonization. At the opposite pole, organic-mineral treatments decrease the colonization parameters by up to half of the organic treatment. All of the colonization parameters show significant correlations, except for the arbuscules/vesicle ratio (0.03). All the applied treatments, except for the organic one, record multiple root segments with a colonization degree lower than 10%. The application of treatments changes the strategy of native colonization from a transfer (40%) and storage (37%) to a predominant storage (50%) for organic treatment, and are mainly proliferative between 38–50% in mixed and mineral treatments. The high amount of mineral components increases also the presence of resistance conditions strategies. The use of mycorrhizal pattern maps, with the inclusion of colonization strategies, presents an important direction in understanding the evolution of mutual relations, and to explore in-depth the efficiency of the whole symbiotic process.
38
Shtark, Oksana, Roman Puzanskiy, Galina Avdeeva, Vladislav Yemelyanov, Alexey Shavarda, Daria Romanyuk, Marina Kliukova et al. "Metabolic Alterations in Pisum sativum Roots during Plant Growth and Arbuscular Mycorrhiza Development". Plants 10, n. 6 (21 maggio 2021): 1033. http://dx.doi.org/10.3390/plants10061033.
Testo completoAbstract (sommario):
Intensive exchange of nutrients is a crucial part of the complex interaction between a host plant and fungi within arbuscular mycorrhizal (AM) symbiosis. For the first time, the present study demonstrates how inoculation with AMF Rhizophagus irregularis affects the pea (Pisum sativum L.) root metabolism at key stages of plant development. These correspond to days 21 (vegetation), 42 (flowering initiation), and 56 (fruiting-green pod). Metabolome profiling was carried out by means of a state-of-the-art GC-MS technique. The content shifts revealed include lipophilic compounds, sugars, carboxylates, and amino acids. The metabolic alterations were principally dependent on the stage of plant development but were also affected by the development of AM fungi, a fact which highlights interaction between symbiotic partners. The comparison of the present data with the results of leaf metabolome profiling earlier obtained did not reveal common signatures of metabolic response to mycorrhization in leaves and roots. We supposed that the feedback for the development and symbiotic interaction on the part of the supraorganismic system (root + AM fungi) was the cause of the difference between the metabolic profile shift in leaf and root cells that our examination revealed. New investigations are required to expand our knowledge of metabolome plasticity of the whole organism and/or system of organisms, and such results might be put to use for the intensification of sustainable agriculture.
39
PEARSON, J. N., e I. JAKOBSEN. "Symbiotic exchange of carbon and phosphorus between cucumber and three arbuscular mycorrhizal fungi". New Phytologist 124, n. 3 (luglio 1993): 481–88. http://dx.doi.org/10.1111/j.1469-8137.1993.tb03839.x.
Testo completo
40
Yurgel, Svetlana N., Jennifer Rice e Michael L. Kahn. "Nitrogen Metabolism in Sinorhizobium meliloti–Alfalfa Symbiosis: Dissecting the Role of GlnD and PII Proteins". Molecular Plant-Microbe Interactions® 25, n. 3 (marzo 2012): 355–62. http://dx.doi.org/10.1094/mpmi-09-11-0249.
Testo completoAbstract (sommario):
To contribute nitrogen for plant growth and establish an effective symbiosis with alfalfa, Sinorhizobium meliloti Rm1021 needs normal operation of the GlnD protein, a bifunctional uridylyltransferase/uridylyl-cleavage enzyme that measures cellular nitrogen status and initiates a nitrogen stress response (NSR). However, the only two known targets of GlnD modification in Rm1021, the PII proteins GlnB and GlnK, are not necessary for effectiveness. We introduced a Tyr→Phe variant of GlnB, which cannot be uridylylated, into a glnBglnK background to approximate the expected state in a glnD-sm2 mutant, and this strain was effective. These results suggested that unmodified PII does not inhibit effectiveness. We also generated a glnBglnK-glnD triple mutant and used this and other mutants to dissect the role of these proteins in regulating the free-living NSR and nitrogen metabolism in symbiosis. The glnD-sm2 mutation was dominant to the glnBglnK mutations in symbiosis but recessive in some free-living phenotypes. The data show that the GlnD protein has a role in free-living growth and in symbiotic nitrogen exchange that does not depend on the PII proteins, suggesting that S. meliloti GlnD can communicate with the cell by alternate mechanisms.
41
Gano-Cohen, Kelsey A., Peter J. Stokes, Mia A. Blanton, Camille E. Wendlandt, Amanda C. Hollowell, John U. Regus, Deborah Kim, Seema Patel, Victor J. Pahua e Joel L. Sachs. "Nonnodulating Bradyrhizobium spp. Modulate the Benefits of Legume-Rhizobium Mutualism". Applied and Environmental Microbiology 82, n. 17 (17 giugno 2016): 5259–68. http://dx.doi.org/10.1128/aem.01116-16.
Testo completoAbstract (sommario):
ABSTRACTRhizobia are best known for nodulating legume roots and fixing atmospheric nitrogen for the host in exchange for photosynthates. However, the majority of the diverse strains of rhizobia do not form nodules on legumes, often because they lack key loci that are needed to induce nodulation. Nonnodulating rhizobia are robust heterotrophs that can persist in bulk soil, thrive in the rhizosphere, or colonize roots as endophytes, but their role in the legume-rhizobium mutualism remains unclear. Here, we investigated the effects of nonnodulating strains on the nativeAcmispon-Bradyrhizobiummutualism. To examine the effects on both host performance and symbiont fitness, we performed clonal inoculations of diverse nonnodulatingBradyrhizobiumstrains onAcmispon strigosushosts and also coinoculated hosts with mixtures of sympatric nodulating and nonnodulating strains. In isolation, nonnodulatingBradyrhizobiumstrains did not affect plant performance. In most cases, coinoculation of nodulating and nonnodulating strains reduced host performance compared to that of hosts inoculated with only a symbiotic strain. However, coinoculation increased host performance only under one extreme experimental treatment. Nearly all estimates of nodulating strain fitness were reduced in the presence of nonnodulating strains. We discovered that nonnodulating strains were consistently capable of coinfecting legume nodules in the presence of nodulating strains but that the fitness effects of coinfection for hosts and symbionts were negligible. Our data suggest that nonnodulating strains most often attenuate theAcmispon-Bradyrhizobiummutualism and that this occurs via competitive interactions at the root-soil interface as opposed toin planta.IMPORTANCERhizobia are soil bacteria best known for their capacity to form root nodules on legume plants and enhance plant growth through nitrogen fixation. Yet, most rhizobia in soil do not have this capacity, and their effects on this symbiosis are poorly understood. We investigated the effects of diverse nonnodulating rhizobia on a native legume-rhizobium symbiosis. Nonnodulating strains did not affect plant growth in isolation. However, compared to inoculations with symbiotic rhizobia, coinoculations of symbiotic and nonnodulating strains often reduced plant and symbiont fitness. Coinoculation increased host performance only under one extreme treatment. Nonnodulating strains also invaded nodule interiors in the presence of nodulating strains, but this did not affect the fitness of either partner. Our data suggest that nonnodulating strains may be important competitors at the root-soil interface and that their capacity to attenuate this symbiosis should be considered in efforts to use rhizobia as biofertilizers.
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Jones, Ross J., e Andrew J. Heyward. "The effects of Produced Formation Water (PFW) on coral and isolated symbiotic dinoflagellates of coral". Marine and Freshwater Research 54, n. 2 (2003): 153. http://dx.doi.org/10.1071/mf02108.
Testo completoAbstract (sommario):
There is concern of the effects of Produced Formation Water (PFW, an effluent of the offshore oil and gas industry) on temperate/tropical marine organisms of the North West Shelf (NWS) of Australia. Little is known of the effects of PFW on tropical marine organisms, especially keystone species. Exposing the coral Plesiastrea versipora to a range (3–50% v/v) of PFW from Harriet A oil platform resulted in a reduction in photochemical efficiency of the symbiotic dinoflagellate algae in hospite (in the coral tissues), assessed as a decrease in the ratio of variable fluorescence (Fv) to maximal fluorescence (Fm) measured using chlorophyll fluorescence techniques. Significant differences were noted at PFW concentrations >12.5% (v/v). In corals where Fv/Fm was significantly lowered by PFW exposure, significant discolouration of the tissues occurred in a subsequent 4-day observation period. The discolouration (coral bleaching) was caused by a loss of the symbiotic dinoflagellates from the tissues, a known sublethal stress response of corals. PFW caused a significant decrease in Fv/Fm in symbiotic dinoflagellates freshly isolated from the coral Heliofungia actiniformis at 6.25% PFW, slightly lower than the studies in hospite. Corals exposed to lower PFW concentrations (range 0.1%–10% PFW v/v) for longer periods (8 days) showed no decrease in Fv/Fm, discolouration, loss of symbiotic dinoflagellates or changes in gross photosynthesis or respiration (measured using O2 exchange techniques). The study demonstrates minor toxicity of PFW from Harriet A oil platform to corals and their symbiotic algae.
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Hohnjec, Natalija, Kolja Henckel, Thomas Bekel, Jerome Gouzy, Michael Dondrup, Alexander Goesmann e Helge Küster. "Transcriptional snapshots provide insights into the molecular basis of arbuscular mycorrhiza in the model legume Medicago truncatula". Functional Plant Biology 33, n. 8 (2006): 737. http://dx.doi.org/10.1071/fp06079.
Testo completoAbstract (sommario):
The arbuscular mycorrhizal (AM) association between terrestrial plants and soil fungi of the phylum Glomeromycota is the most widespread beneficial plant–microbe interaction on earth. In the course of the symbiosis, fungal hyphae colonise plant roots and supply limiting nutrients, in particular phosphorus, in exchange for carbon compounds. Owing to the obligate biotrophy of mycorrhizal fungi and the lack of genetic systems to study them, targeted molecular studies on AM symbioses proved to be difficult. With the emergence of plant genomics and the selection of suitable models, an application of untargeted expression profiling experiments became possible. In the model legume Medicago truncatula, high-throughput expressed sequence tag (EST)-sequencing in conjunction with in silico and experimental transcriptome profiling provided transcriptional snapshots that together defined the global genetic program activated during AM. Owing to an asynchronous development of the symbiosis, several hundred genes found to be activated during the symbiosis cannot be easily correlated with symbiotic structures, but the expression of selected genes has been extended to the cellular level to correlate gene expression with specific stages of AM development. These approaches identified marker genes for the AM symbiosis and provided the first insights into the molecular basis of gene expression regulation during AM.
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Nichols, Deborah L. "RETHINKING HUITZILOPOCHTLI'S CONQUEST: ELIZABETH M. BRUMFIEL, SOCIAL THEORY, AND THE AZTECS OF MEXICO". Ancient Mesoamerica 27, n. 1 (2016): 153–62. http://dx.doi.org/10.1017/s0956536116000122.
Testo completoAbstract (sommario):
AbstractElizabeth M. Brumfiel began work in Aztec studies by tackling nothing less than the economic symbiotic model of Aztec exchange and specialization. Her findings at Huexotla and Xico questioned this model and in its place Brumfiel focused on the politics of exchange and strategies of both state power and commoner households. Her long-term archaeological project at Xaltocan built on and expanded those themes by applying social theories to understand Aztec society, and inequalities more generally, from a bottom-up agency perspective. These intellectual commitments also guided Brumfiel's engagement with community archaeology and her professional leadership.
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Egger, Keith N., e David S. Hibbett. "The evolutionary implications of exploitation in mycorrhizas". Canadian Journal of Botany 82, n. 8 (1 agosto 2004): 1110–21. http://dx.doi.org/10.1139/b04-056.
Testo completoAbstract (sommario):
Some views of mutualism, where the fitness of two symbiotic partners is higher in association than when apart, assume that they necessarily evolve towards greater benefit for the partners. Most mutualisms, however, seem prone to conflicts of interest that destabilize the partnership. These conflicts arise in part because mutualistic outcomes are conditional, depending upon complex interactions between environmental, developmental, and genotypic factors. Mutualisms are also subject to exploitation or cheating. Although various compensating mechanisms have been proposed to explain how mutualism can be maintained in the presence of exploiters, none of these mechanisms can eliminate exploitation. In this paper we explore various compensating mechanisms in mycorrhizas, examine the evidence for exploitation in mycorrhizas, and conclude that mycorrhizal mutualisms exhibit characteristics that are more consistent with a concept of reciprocal parasitism. We propose that researchers should not assume mycorrhizas are mutualistic based upon structural characteristics or limited functional studies showing bilateral exchange and should view mycorrhizas as occupying a wider range on the symbiotic continuum, including commensalism and antagonism. We recommend that comparative studies of mycorrhizas incorporate other types of root associations that have traditionally been considered antagonistic.Key words: mycorrhizas, mutualism, exploiters, compensating mechanisms, symbiotic continuum.
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Schofield, Peter R., Alan H. Gibson, William F. Dudman e John M. Watson. "Evidence for Genetic Exchange and Recombination of Rhizobium Symbiotic Plasmids in a Soil Population". Applied and Environmental Microbiology 53, n. 12 (1987): 2942–47. http://dx.doi.org/10.1128/aem.53.12.2942-2947.1987.
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Nelson, Corey, Ana Giraldo-Silva e Ferran Garcia-Pichel. "A symbiotic nutrient exchange within the cyanosphere microbiome of the biocrust cyanobacterium, Microcoleus vaginatus". ISME Journal 15, n. 1 (23 settembre 2020): 282–92. http://dx.doi.org/10.1038/s41396-020-00781-1.
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Bucheli, Juan Fernando. "CONDITIONAL CASH TRANSFER SCHEMES AND THE POLITICISATION OF POVERTY REDUCTION STRATEGIES SCHEMES AND POLITICISATION OF POVERTY REDUCTION STRATEGIES". Análisis Político 28, n. 83 (1 gennaio 2015): 19–31. http://dx.doi.org/10.15446/anpol.v28n83.51641.
Testo completoAbstract (sommario):
Conditional Cash Transfers (CCTs) in Latin America has been marked by a closed top-down process led by coalitions of politicians and technocrats who have chosen patronage relationships as the most convenient interaction with beneficiaries of social programmes. The existence of this type of relationship forces beneficiaries to take part in long-term political alliances in exchange for economic benefits. What seems to be a symbiotic relationship for the parties ultimately can have negative consequences in terms of democratic values and a financial opportunity cost to implement more efficient social investment. The more the exchange persists, the more permanent welfare dependency will prevail in the region.
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Matthews, Jennifer L., Camerron M. Crowder, Clinton A. Oakley, Adrian Lutz, Ute Roessner, Eli Meyer, Arthur R. Grossman, Virginia M. Weis e Simon K. Davy. "Optimal nutrient exchange and immune responses operate in partner specificity in the cnidarian-dinoflagellate symbiosis". Proceedings of the National Academy of Sciences 114, n. 50 (20 novembre 2017): 13194–99. http://dx.doi.org/10.1073/pnas.1710733114.
Testo completoAbstract (sommario):
The relationship between corals and dinoflagellates of the genusSymbiodiniumis fundamental to the functioning of coral ecosystems. It has been suggested that reef corals may adapt to climate change by changing their dominant symbiont type to a more thermally tolerant one, although the capacity for such a shift is potentially hindered by the compatibility of different host-symbiont pairings. Here we combined transcriptomic and metabolomic analyses to characterize the molecular, cellular, and physiological processes that underlie this compatibility, with a particular focus onSymbiodinium trenchii, an opportunistic, thermally tolerant symbiont that flourishes in coral tissues after bleaching events. Symbiont-free individuals of the sea anemoneExaiptasia pallida(commonly referred to as Aiptasia), an established model system for the study of the cnidarian-dinoflagellate symbiosis, were colonized with the “normal” (homologous) symbiontSymbiodinium minutumand the heterologousS. trenchii. Analysis of the host gene and metabolite expression profiles revealed that heterologous symbionts induced an expression pattern intermediate between the typical symbiotic state and the aposymbiotic state. Furthermore, integrated pathway analysis revealed that increased catabolism of fixed carbon stores, metabolic signaling, and immune processes occurred in response to the heterologous symbiont type. Our data suggest that both nutritional provisioning and the immune response induced by the foreign “invader” are important factors in determining the capacity of corals to adapt to climate change through the establishment of novel symbioses.
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KUNG, SHIAO-CHUAN. "Evaluation of a team model of digital language exchange". ReCALL 14, n. 2 (novembre 2002): 315–26. http://dx.doi.org/10.1017/s0958344002000824.
Testo completoAbstract (sommario):
This paper describes an online collaborative model designed to allow meaningful, authentic interactions between college English as a Foreign Language (EFL) students and adult native speakers of English. The program uses technology to bridge the gap between the need of EFL students to interact with native speakers for successful language learning and the geographical distance of EFL classrooms. The two groups of participants were brought together in a symbiotic relationship enabled and shaped by an online collaborative learning environment. This study employed two 4-member teams collaborating on an electronic bulletin board to address problems such as lack of response and lack of purpose that current models of online exchange face. Findings indicate that the team model is a viable alternative to one-to-one or many-to-many correspondence. They also suggest that collaborative activities may play an important role in fostering meaningful and lasting interactions.