Plant-Microbe Symbiosis
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La plus grosse truffe blanche au monde vendue 61.250 dollars à New York

La plus grosse truffe blanche au monde vendue 61.250 dollars à New York | Plant-Microbe Symbiosis | Scoop.it
La plus grosse truffe blanche au monde, pesant 1,89 kilo, a été vendue aux enchères à New York pour 61.250 dollars, a annoncé samedi la maison Sotheby's qui organisait la vente.
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The biggest truffle ever...

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Plant-Microbe Symbiosis
Beneficial associations between plants and microbes
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Epidermal auxin biosynthesis facilitates rhizobial infection in Lotus japonicus

Epidermal auxin biosynthesis facilitates rhizobial infection in Lotus japonicus | Plant-Microbe Symbiosis | Scoop.it
Symbiotic nitrogen fixation in legumes requires nodule organogenesis to be coordinated with infection by rhizobia. The plant hormone auxin influences symbiotic infection, but the precise timing of auxin accumulation and the genetic network governing it remain unclear. We used a Lotus japonicus optimised variant of the DII‐based auxin accumulation sensor and identified a rapid accumulation of auxin in the epidermis, specifically in the root hair cells. This auxin accumulation occurs in the infected root hairs during rhizobia invasion, while Nod factor application induces this response across a broader range of root hairs. Using the DR5 auxin responsive promoter, we demonstrate that activation of auxin signalling also occurs specifically in infected root hairs. Analysis of root hair transcriptome data identified induction of an auxin biosynthesis gene of the Tryptophan Amino‐transferase Related (LjTar1) family following both bacteria inoculation and Nod factor treatment. Genetic analysis showed that both expression of the LjTar1 biosynthesis gene and the auxin response requires Nod factor perception, while common symbiotic pathway transcription factors are only partially required or act redundantly to initiate auxin accumulation. Using a chemical genetics approach, we confirmed that auxin biosynthesis has a functional role in promoting symbiotic infection events in the epidermis.

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Mycorrhizal lipochitinoligosaccharides (LCOs) depolarize root hairs of Medicago truncatula

Mycorrhizal lipochitinoligosaccharides (LCOs) depolarize root hairs of Medicago truncatula | Plant-Microbe Symbiosis | Scoop.it
Arbuscular Mycorrhiza and Root Nodule Symbiosis are symbiotic interactions with a high benefit for plant growth and crop production. Thus, it is of great interest to understand the developmental process of these symbioses in detail. We analysed very early symbiotic responses of Medicago truncatula root hair cells, by stimulation with lipochitinoligosaccharides specific for the induction of nodules (Nod-LCOs), or the interaction with mycorrhiza (Myc-LCOs). Intracellular micro electrodes were used, in combination with Ca2+ sensitive reporter dyes, to study the relations between cytosolic Ca2+ signals and membrane potential changes. We found that sulfated Myc- as well as Nod-LCOs initiate a membrane depolarization, which depends on the chemical composition of these signaling molecules, as well as the genotype of the plants that were studied. A successive application of sulfated Myc-LCOs and Nod-LCOs resulted only in a single transient depolarization, indicating that Myc-LCOs can repress plasma membrane responses to Nod-LCOs. In contrast to current models, the Nod-LCO-induced depolarization precedes changes in the cytosolic Ca2+ level of root hair cells. The Nod-LCO induced membrane depolarization thus is most likely independent of cytosolic Ca2+ signals and nuclear Ca2+ spiking.

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I don't know why they say that this is "in contrast to current models"... This is totally fits the current models. See the work of Ehrhardt and Long.

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Arbuscular mycorrhizal fungal communities in tropical rain forest are resilient to slash-and-burn agriculture

Certain forestry and agricultural practices are known to affect arbuscular mycorrhizal (AM) fungal communities, but the effects of deforestation – including slash-and-burn management and other more severe disturbances – in tropical rain forests are poorly understood. We addressed the effects of anthropogenic disturbance on rain-forest AM fungal communities in French Guiana, by comparing mature tropical rain forest, slash-and-burn (5 y old) and clearcut areas (8 y old). A total of 36 soil samples were collected in six plots and sequenced using a high throughput 454-pyrosequencing platform. A total of 32649 sequences from 103 AM fungal virtual taxa (VT) were recorded. Whereas alpha diversity of AM fungi did not decrease due to land-use intensification, with average richness ranging from 17 to 21 taxa per plot, beta diversity (average distance to multivariate centroid) dropped by 28% from 0.46 in rain forest to 0.33 under clearcutting. AM fungal community composition was correlated with land use and soil chemical properties. Clearcut areas were characterized by the more frequent occurrence of specialist AM fungi, compared with mature forest or slash-and-burn areas. Specifically, clearcuts contained the highest proportions of VT that were geographic (21%), habitat (31%), abundance (97%) or host (97%) specialists based on VT metadata contained in the MaarjAM database. This suggests that certain AM fungi with narrow ecological niches have traits that allow them to exploit conditions of severe disturbance. In conclusion, slash-and-burn management appears to allow diverse AM fungal communities to persist, and may favour regeneration of tropical rain forest after abandonment. More severe disturbance in the form of clearcutting resulted in marked changes in AM fungal communities.

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Tomato CYCLOPS/IPD3 is required for mycorrhizal symbiosis but not tolerance to Fusarium wilt in mycorrhiza-deficient tomato mutant rmc

Mycorrhizal symbiosis requires several common symbiosis genes including CYCLOPS/IPD3. The reduced mycorrhizal colonisation (rmc) tomato mutant has a deletion of five genes including CYCLOPS/IPD3, and rmc is more susceptible to Fusarium wilt than its wild-type parental line. This study investigated the genetic defects leading to both fungal interaction phenotypes and whether these were separable. Complementation was performed in rmc to test the requirement for CYCLOPS/IPD3 in mycorrhiza formation and Fusarium wilt tolerance. Promoter analysis via GFP expression in roots was conducted to determine the role of native regulatory elements in the proper functioning of CYCLOPS/IPD3. CYCLOPS/IPD3 regulated by its native promoter, but not a 2×35S promoter, restores mycorrhizal association in rmc. GFP regulated by the 2×35S promoter is not expressed in epidermal cells of roots, indicating that expression of CYCLOPS/IPD3 in these cells is required for colonisation by the fungi utilised in this research. CYCLOPS/IPD3 did not restore Fusarium wilt tolerance, however, showing that the genetic requirements for mycorrhizal association and Fusarium wilt tolerance are different. Our results confirm the expected role of CYCLOPS/IPD3 in mycorrhizal symbiosis and suggest that Fusarium tolerance is conferred by one of the other four genes affected by the deletion.

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To be honest... glad to hear that :-)

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Exometabolomic Profiling of Bacterial Strains as Cultivated Using Arabidopsis Root Extract as the Sole Carbon Source

Exometabolomic Profiling of Bacterial Strains as Cultivated Using Arabidopsis Root Extract as the Sole Carbon Source | Plant-Microbe Symbiosis | Scoop.it
The ability of microorganisms to use root-derived metabolites as growth substrates is a key trait for success in the rhizospheric niche. However, few studies describe which specific metabolites are consumed or to what degree microbial strains differ in their substrate consumption patterns. Here, we present a liquid chromatography-mass spectrometry (MS) exometabolomic study of three bacterial strains cultivated using either glucose or Arabidopsis thaliana root extract as the sole carbon source. Two of the strains were previously isolated from field-grown Arabidopsis roots, the other is Escherichia coli, included as a comparison. When cultivated on root extract, a set of 62 MS features were commonly taken up by all three strains, with m/z values matching components of central metabolism (including amino acids and purine or pyrimidine derivatives). Escherichia coli took up very few MS features outside this commonly consumed set, whereas the root-inhabiting strains took up a much larger number of MS features, many with m/z values matching plant-specific metabolites. These measurements define the metabolic niche that each strain potentially occupies in the rhizosphere. Furthermore, we document many MS features released by these strains that could play roles in cross-feeding, antibiosis, or signaling. We present our methodological approach as a foundation for future studies of rhizosphere exometabolomics.

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Arbuscular mycorrhizal fungi mediate herbivore‐induction of plant defenses differently above and belowground

Plants are exposed to herbivores and symbionts above and belowground. Herbivores aboveground alter plant defenses in both leaves and roots, affecting plant–herbivore interactions above and belowground. Root symbionts, such as arbuscular mycorrhizal fungi (AMF), also influence the defenses of leaves and roots, and alter plant responses to herbivory. However, we lack an understanding of how AMF mediate plant responses to herbivores simultaneously in above and belowground plant tissues, despite the ubiquity of such interactions and their consequences for ecological communities. In a full factorial experiment, we subjected plants of four milkweed (Asclepias) species under three levels of AMF inoculum availability to damage by aphids Aphis nerii, caterpillars Danaus plexippus, or no herbivores. We then measured foliar and root cardenolides (chemical defenses), leaf toughness, latex exudation (physical defenses), foliar carbon, nitrogen, and phosphorous concentrations, plant biomass, and levels of AMF colonization of roots.

Plants inoculated with AMF generally produced tougher leaves with higher cardenolide concentrations than did plants without AMF. In contrast, root cardenolides were altered by AMF inoculum availability in a plant species‐specific manner. The relative induction or suppression of foliar cardenolides and leaf toughness by herbivores was altered strongly by the level of AMF inoculum available to plants. However, AMF did not influence caterpillar‐induction or aphid‐suppression of root cardenolides. In addition, herbivore feeding induced substantial changes in levels of AMF colonization of roots in a plant species‐specific manner. We demonstrate that the availability of AMF in soil alters herbivore induction and suppression of plant defenses strongly, and does so differently in above and belowground plant tissues. Furthermore, we show that herbivore feeding alters levels of AMF colonization substantially, completing a feedback loop between above and belowground organisms. Our study suggests that indirect interactions between AMF and herbivores may have community‐wide consequences by altering plant phenotype above and belowground.
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Mechanistic insights on plant root colonization by bacterial endophytes: a symbiotic relationship for sustainable agriculture

Plant–microbe and soil interactions are one of the oldest muse for multi-disciplinary researchers. Plant growth promoting microorganisms influence the host physiology by secreting regulatory chemical signals in the vicinity of plant roots and play a key role in the enhancement of plant growth and expansion. The present review deals with the in-depth understanding of steps involved in host tissues colonization by bacterial endophytes. The molecular insights of these events, particularly for endophytic bacteria, are poorly documented till date. The endophytic bacteria must coexist with the host plant and capable of colonizing the internal plant tissues without being recognized as a pathogen. A proper understanding of exchange of signals between the host plant and bacterial communities is required which may facilitate the development of new strategies to promote beneficial interactions between them. This knowledge can be instrumental in agricultural practices as well as for phytoremediation of pollutants. Keeping these facts in mind, the present review attempts to explore the systematic understanding of steps involved and molecular insights of plant colonization events by endophytic bacteria. We conclude that molecular mechanisms and factors affecting endophytic bacterial colonization deserve more research attention in order to exploit their beneficial aspects for sustainable agriculture and environment.

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Nitrogen-fixing populations of Planctomycetes and Proteobacteria are abundant in surface ocean metagenomes

Nitrogen-fixing populations of Planctomycetes and Proteobacteria are abundant in surface ocean metagenomes | Plant-Microbe Symbiosis | Scoop.it

Nitrogen fixation in the surface ocean impacts global marine nitrogen bioavailability and thus microbial primary productivity. Until now, cyanobacterial populations have been viewed as the main suppliers of bioavailable nitrogen in this habitat. Although PCR amplicon surveys targeting the nitrogenase reductase gene have revealed the existence of diverse non-cyanobacterial diazotrophic populations, subsequent quantitative PCR surveys suggest that they generally occur in low abundance. Here, we use state-of-the-art metagenomic assembly and binning strategies to recover nearly one thousand non-redundant microbial population genomes from the TARA Oceans metagenomes. Among these, we provide the first genomic evidence for non-cyanobacterial diazotrophs inhabiting surface waters of the open ocean, which correspond to lineages within the Proteobacteria and, most strikingly, the Planctomycetes. Members of the latter phylum are prevalent in aquatic systems, but have never been linked to nitrogen fixation previously. Moreover, using genome-wide quantitative read recruitment, we demonstrate that the discovered diazotrophs were not only widespread but also remarkably abundant (up to 0.3% of metagenomic reads for a single population) in both the Pacific Ocean and the Atlantic Ocean northwest. Our results extend decades of PCR-based gene surveys, and substantiate the importance of heterotrophic bacteria in the fixation of nitrogen in the surface ocean.

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Contrasting effects of ectomycorrhizal fungi on early and late stage decomposition in a boreal forest

Contrasting effects of ectomycorrhizal fungi on early and late stage decomposition in a boreal forest | Plant-Microbe Symbiosis | Scoop.it
Symbiotic ectomycorrhizal fungi have received increasing attention as regulators of below-ground organic matter storage. They are proposed to promote organic matter accumulation by suppressing saprotrophs, but have also been suggested to play an active role in decomposition themselves. Here we show that exclusion of tree roots and associated ectomycorrhizal fungi in a boreal forest increased decomposition of surface litter by 11% by alleviating nitrogen limitation of saprotrophs–a “Gadgil effect”. At the same time, root exclusion decreased Mn-peroxidase activity in the deeper mor layer by 91%. Our results show that ectomycorrhizal fungi may hamper short-term litter decomposition, but also support a crucial role of ectomycorrhizal fungi in driving long-term organic matter oxidation. These observations stress the importance of ectomycorrhizal fungi in regulation of below-ground organic matter accumulation. By different mechanisms they may either hamper or stimulate decomposition, depending upon stage of decomposition and location in the soil profile.

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A Lotus japonicus E3 ligase interacts with the Nod factor receptor 5 and positively regulates nodulation

Post-translational modification of receptor proteins is involved in activation and de-activation of signaling systems in plants. Both ubiquitination and deubiquitination have been implicated in plant interactions with pathogens and symbionts. Here we present LjPUB13, a PUB ARMADILLO repeat E3 ligase that specifically ubiquitinates the kinase domain of the Nod Factor receptor NFR5 and has a direct role in nodule organogenesis events in Lotus japonicus. Phenotypic analyses of three LORE1 retroelement insertion plant lines revealed that pub13 plants display delayed and reduced nodulation capacity and retarded growth. LjPUB13 expression is spatially regulated during symbiosis with Mesorhizobium loti, with increased levels in young developing nodules. Thus, LjPUB13 is an E3 ligase with a positive regulatory role during the initial stages of nodulation in L. japonicus.
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Phylogenomics reveals multiple losses of nitrogen-fixing root nodule symbiosis

The root nodule symbiosis of plants with nitrogen-fixing bacteria impacts global nitrogen cycles and food production but is restricted to a subset of genera within a single clade of flowering plants. To explore the genetic basis for this scattered occurrence, we sequenced the genomes of ten plant species covering the diversity of nodule morphotypes, bacterial symbionts and infection strategies. In a genome-wide comparative analysis of a total of 37 plant species, we discovered signatures of multiple independent loss-of-function events in the indispensable symbiotic regulator NODULE INCEPTION ( NIN ) in ten out of 13 genomes of non-nodulating species within this clade. The discovery that multiple independent losses shaped the present day distribution of nitrogen-fixing root nodule symbiosis in plants reveals a phylogenetically wider distribution in evolutionary history and a so far underestimated selection pressure against this symbiosis.
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Nodulated Root Earrings - Science Jewelry

Nodulated Root Earrings - Science Jewelry | Plant-Microbe Symbiosis | Scoop.it
Nodulated Root Earrings - Science Jewelry (EXQLP35EC) by Ontogenie on Shapeways. Learn more before you buy, or discover other cool products in Earrings.
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Transcriptome analysis reveals class IX ethylene response factors show specific up-regulation in resistant but not susceptible Medicago truncatula lines following infection with Rhizoctonia solani

The fungal pathogen Rhizoctonia solani AG8 causes substantial losses to cereal and legume production in Australia and the Pacific Northwest of the United States of America. Mutant analyses have revealed a critical role for ethylene mediated defence signalling for resistance to R. solani AG8 in the model legume Medicago truncatula which is, at least in part, mediated by ethylene dependent accumulation of isoflavonoids. In this study we investigate the potential for members of the ethylene response transcription factor (ERF) family in mediating the isoflavonoid and defence response. A strong and early Rhizoctonia-responsive expression pattern was observed for many of the class IX ERFs in the moderately resistant wild type line A17, while the ethylene insensitive and highly susceptible mutant sickle (skl) showed a very limited regulation of this class. Conversely, the skl mutant demonstrated up-regulation of class II ERFs known to act as transcriptional repressors. Analysis of the presence of the GCC box promoter element, thought to be responsible for ERF binding and transcriptional activity, in genes differentially regulated in A17 suggests indirect or alternative mechanisms of ERF mediated gene regulation may be contributing to the large scale transcriptional adaptation of A17 following R. solani AG8 infection. Comparison of the expression profile with that following infection of A17 and skl with the symbiotic bacterium Sinorhizobium medicae suggests that legumes have adapted the ERF family to perform diverse roles to balance defence against pathogens and symbiosis with beneficial microorganisms in the same root tissue.

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Ectomycorrhizal associations in the tropics – biogeography, diversity patterns and ecosystem roles

Ectomycorrhizal associations in the tropics – biogeography, diversity patterns and ecosystem roles | Plant-Microbe Symbiosis | Scoop.it
Ectomycorrhizal (ECM) associations were historically considered rare or absent from tropical ecosystems. Although most tropical forests are dominated by arbuscular mycorrhizal (AM) trees, ECM associations are widespread and found in all tropical regions. Here, we highlight emerging patterns of ECM biogeography, diversity and ecosystem functions, identify knowledge gaps, and offer direction for future research. At the continental and regional scales, tropical ECM systems are highly diverse and vary widely in ECM plant and fungal abundance, diversity, composition and phylogenetic affinities. We found strong regional differences among the dominant host plant families, suggesting that biogeographical factors strongly influence tropical ECM symbioses. Both ECM plants and fungi also exhibit strong turnover along altitudinal and soil fertility gradients, suggesting niche differentiation among taxa. Ectomycorrhizal fungi are often more abundant and diverse in sites with nutrient‐poor soils, suggesting that ECM associations can optimize plant nutrition and may contribute to the maintenance of tropical monodominant forests. More research is needed to elucidate the diversity patterns of ECM fungi and plants in the tropics and to clarify the role of this symbiosis in nutrient and carbon cycling.

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Systemic Calcium Wave Propagation in Physcomitrella patens

The adaptation to dehydration and rehydration cycles represents a key step in the evolution of photosynthetic organisms and require the development of mechanisms by which to sense external stimuli and translate them into signaling components. In this study, we used genetically encoded fluorescent sensors to detect specific transient increases in the Ca2+ concentration in the moss Physcomitrella patens upon dehydration and rehydration treatment. Observation of the entire plant in a single time-series acquisition revealed that various cell types exhibited different sensitivities to osmotic stress and that Ca2+ waves originated from the basal part of the gametophore and were directionally propagated towards the top of the plant. Under similar conditions, the vascular plant Arabidopsis thaliana exhibited Ca2+ waves that propagated at a higher speed than those of P. patens. Our results suggest that systemic Ca2+ propagation occurs in plants even in the absence of vascular tissue even though the rates can be different.

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Horizontal Gene Transfer From Bacteria and Plants to the Arbuscular Mycorrhizal Fungus Rhizophagus irregularis

Horizontal Gene Transfer From Bacteria and Plants to the Arbuscular Mycorrhizal Fungus Rhizophagus irregularis | Plant-Microbe Symbiosis | Scoop.it
Arbuscular mycorrhizal fungi (AMF) belong to Glomeromycotina, and are mutualistic symbionts of many land plants. Associated bacteria accompany AMF during their lifecycle to establish a robust tripartite association consisting of fungi, plants and bacteria. Physical association among this trinity provides possibilities for the exchange of genetic materials. However, very few horizontal gene transfer (HGT) from bacteria or plants to AMF has been reported yet. In this study, we complement existing algorithms by developing a new pipeline, Blast2hgt, to efficiently screen for putative horizontally derived genes from a whole genome. Genome analyses of the glomeromycete Rhizophagus irregularis identified 19 fungal genes that had been transferred between fungi and bacteria/plants, of which seven were obtained from bacteria. Another 18 R. irregularis genes were found to be recently acquired from either plants or bacteria. In the R. irregularis genome, gene duplication has contributed to the expansion of three foreign genes. Importantly, more than half of the R. irregularis foreign genes were expressed in various transcriptomic experiments, suggesting that these genes are functional in R. irregularis. Functional annotation and available evidence showed that these acquired genes may participate in diverse but fundamental biological processes such as regulation of gene expression, mitosis and signal transduction. Our study suggests that horizontal gene influx through endosymbiosis is a source of new functions for R. irregularis, and HGT might have played a role in the evolution and symbiotic adaptation of this arbuscular mycorrhizal fungus.

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Nitrogen and phosphate metabolism in ectomycorrhizas

Nutrient homeostasis is essential for fungal cells and thus tightly adapted to the local demand in a mycelium with hyphal specialization. Based on selected ectomycorrhizal (ECM) fungal models, we outlined current concepts of nitrogen and phosphate nutrition and their limitations, and included knowledge from Baker's yeast when major gaps had to be filled. We covered the entire pathway from nutrient mobilization, import and local storage, distribution within the mycelium and export at the plant–fungus interface. Even when nutrient import and assimilation were broad issues for ECM fungi, we focused mainly on nitrate and organic phosphorus uptake, as other nitrogen/phosphorus (N/P) sources have been covered by recent reviews. Vacuolar N/P storage and mobilization represented another focus point of this review. Vacuoles are integrated into cellular homeostasis and central for an ECM mycelium at two locations: soil‐growing hyphae and hyphae of the plant–fungus interface. Vacuoles are also involved in long‐distance transport. We further discussed potential mechanisms of bidirectional long‐distance nutrient transport (distances from millimetres to metres). A final focus of the review was N/P export at the plant–fungus interface, where we compared potential efflux mechanisms and pathways, and discussed their prerequisites.

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A MUST read....

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Deciphering the tri-dimensional effect of endophytic Streptomyces sp. on chickpea for plant growth promotion, helper effect with Mesorhizobium ciceri and host-plant resistance induction against Bot...

Deciphering the tri-dimensional effect of endophytic Streptomyces sp. on chickpea for plant growth promotion, helper effect with Mesorhizobium ciceri and host-plant resistance induction against Bot... | Plant-Microbe Symbiosis | Scoop.it
A total of 219 endophytic actinobacteria, isolated from roots, stems and leaves of chickpea, were characterized for antagonistic potential against Botrytis cinerea, causal organism of Botrytis grey mold (BGM) disease, in chickpea. Among them, three most potential endophytes, AUR2, AUR4 and ARR4 were further characterized for their plant growth-promoting (PGP) and nodulating potentials and host-plant resistance against B. cinerea, in chickpea. The sequences of 16 S rDNA gene of the three endophytes were matched with Streptomyces but different species. In planta, the isolate AUR4 alone was able to significantly enhance PGP traits including seed numbers (11.8 vs. 9.8/Plant), seed weight (8 vs. 6.8 g/Plant), pod numbers (13.6 vs. 11.5/Plant), pod weight (9.3 vs. 7.5 g/Plant) and biomass (10.9 vs. 8 g/Plant) over the un-inoculated control in chickpea genotype JG11. Interestingly, consortium of the selected endophytes, AUR2, AUR4 and ARR4 were found less effective than single inoculation. Co-inoculation of the selected endophytes with Mesorhizobium ciceri significantly enhanced nodulation and nitrogenase activity in five chickpea genotypes including ICCV2, ICCV10, ICC4958, Annigeri and JG11 over the un-inoculated control. The selected endophytes showed antagonistic potential in planta by significant reduction of disease incidence (28─52%) in both single inoculation and consortium treatments over the un-inoculated control across the genotypes ICC4954 (susceptible), ICCV05530 (moderately resistant) and JG11 (unknown resistance). Further, antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase, phenylalanine ammonia-lyase and polyphenol oxidase and phenolics were found induced in the leaves of chickpea inoculated with selected endophytes over un-inoculated control. Principal component analysis revealed that, the antioxidant enzymes and phenolics were found in the magnitude of ICC4954 < JG11 < ICCV05530 which correlates with their resistance level. The selected endophytes enhanced the plant growth and also host plant resistance against BGM in chickpea.

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NUCLEAR FACTOR-Y: still complex after all these years?

NUCLEAR FACTOR-Y: still complex after all these years? | Plant-Microbe Symbiosis | Scoop.it
The NUCLEAR FACTOR-Y (NF-Y) families of transcription factors are important regulators of plant development and physiology. Though NF-Y regulatory roles have recently been suggested for numerous aspects of plant biology, their roles in flowering time, early seedling development, stress responses, hormone signaling, and nodulation are the best characterized. The past few years have also seen significant advances in our understanding of the mechanistic function of the NF-Y, and as such, increasingly complex and interesting questions are now more approachable. This review will primarily focus on these developmental, physiological, and mechanistic roles of the NF-Y in recent research.

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Actinobacteria Associated With Arbuscular Mycorrhizal Funneliformis mosseae Spores, Taxonomic Characterization and Their Beneficial Traits to Plants: Evidence Obtained From Mung Bean (V... 

Actinobacteria Associated With Arbuscular Mycorrhizal Funneliformis mosseae Spores, Taxonomic Characterization and Their Beneficial Traits to Plants: Evidence Obtained From Mung Bean (V...  | Plant-Microbe Symbiosis | Scoop.it
In this study, we report on the isolation of actinobacteria obtained from spores of Funneliformis mosseae and provide evidence for their potential in agricultural uses as plant growth promoters in vitro and in vivo. Actinobacteria were isolated from spores of F. mosseae using the dilution plate technique and media designed for the selective isolation of members of specific actinobacterial taxa. Six strains namely 48, S1, S3, S4, S4-1 and SP, were isolated and identified based on16S rRNA gene sequences. Phylogenetic analysis showed that isolate SP belonged to the genus Pseudonocardia with P. nantongensis KLBMP 1282T as its closest neighbor. The remaining isolates belonged to the genus Streptomyces. Two isolates, 48 and S3 were most closely related to S. thermocarboxydus DSM 44293T. Isolates S4 and S4-1 shared the highest 16S RNA gene similarity with S. pilosus NBRC 127772T. Isolate S1 showed its closest relationship with the type strain of S. spinoverrucosus NBRC14228T. The ability of these isolates to produce indole-3-acetic acid (IAA), siderophores and the ability to solubilize phosphate in vitro were examined. All isolates produced siderophores, four isolates produced IAA and two isolates solubilized inorganic phosphate at varying levels. S. thermocarboxydus isolate S3 showed the highest IAA production with high activities of phosphate solubilization and siderophore production. The inoculation of mung beans (Vigna radiata) with this strain resulted in a significan
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Know your enemy, embrace your friend: using omics to understand how plants respond differently to pathogenic and mutualistic microorganisms

Microorganisms, or ‘microbes’, have formed intimate associations with plants throughout the length of their evolutionary history. In extant plant systems microbes still remain an integral part of the ecological landscape, impacting plant health, productivity and long‐term fitness. Therefore, to properly understand the genetic wiring of plants, we must first determine what perception systems plants have evolved to parse beneficial from commensal from pathogenic microbes. In this review, we consider some of the most recent advances in how plants respond at the molecular level to different microbial lifestyles. Further, we cover some of the means by which microbes are able to manipulate plant signaling pathways through altered destructiveness and nutrient sinks, as well as the use of effector proteins and micro‐RNAs (miRNAs). We conclude by highlighting some of the major questions still to be answered in the field of plant‐microbe research, and suggest some of the key areas that are in greatest need of further research investment. The results of these proposed studies will have impacts in a wide range of plant research disciplines and will, ultimately, translate into stronger agronomic crops and forestry stock, with immune perception and response systems bred to foster beneficial microbial symbioses while repudiating pathogenic symbioses.

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MtCAS31 Aids Symbiotic Nitrogen Fixation by Protecting the Leghemoglobin MtLb120-1 Under Drought Stress in Medicago truncatula

MtCAS31 Aids Symbiotic Nitrogen Fixation by Protecting the Leghemoglobin MtLb120-1 Under Drought Stress in Medicago truncatula | Plant-Microbe Symbiosis | Scoop.it
Symbiotic nitrogen fixation (SNF) in legume root nodules injects millions of tons of nitrogen into agricultural lands and provides ammonia to non-legume crops under N-deficient conditions. During plant growth and development, environmental stresses, such as drought, salt, cold, and heat stress are unavoidable. This raises an interesting question as to how the legumes cope with the environmental stress along with SNF. Under drought stress, dehydrin proteins are accumulated, which function as protein protector and osmotic substances. In this study, we found that the dehydrin MtCAS31 (cold-acclimation-specific 31) functions in SNF in Medicago truncatula during drought stress. We found that MtCAS31 is expressed in nodules and interacts with leghemoglobin MtLb120-1. The interaction between the two proteins protects MtLb120-1 from denaturation under thermal stress in vivo. Compared to wild type, cas31 mutants display a lower nitrogenase activity, a lower ATP/ADP ratio, higher expression of nodule senescence genes and higher accumulation of amyloplasts under dehydration conditions. The results suggested that MtCAS31 protects MtLb120-1 from the damage of drought stress. We identified a new function for dehydrins in SNF under drought stress, which enriches the understanding of the molecular mechanism of dehydrins.

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Nutrient demand and fungal access to resources control the carbon allocation to the symbiotic partners in tripartite interactions of Medicago truncatula

Legumes form tripartite interactions with arbuscular mycorrhizal (AM) fungi and rhizobia, and both root symbionts exchange nutrients against carbon from their host. The carbon costs of these interactions are substantial, but our current understanding of how the host controls its carbon allocation to individual root symbionts is limited. We examined nutrient uptake and carbon allocation in tripartite interactions of Medicago truncatula under different nutrient supply conditions, and when the fungal partner had access to nitrogen, and followed the gene expression of several plant transporters of the SUT and SWEET family. Tripartite interactions led to synergistic growth responses and stimulated the phosphate and nitrogen uptake of the plant. Plant nutrient demand but also fungal access to nutrients played an important role for the carbon transport to different root symbionts, and the plant allocated more carbon to rhizobia under nitrogen demand, but more carbon to the fungal partner when nitrogen was available. These changes in carbon allocation were consistent with changes in the SUT and SWEET expression. Our study provides important insights into how the host plant controls its carbon allocation under different nutrient supply conditions and changes its carbon allocation to different root symbionts to maximize its symbiotic benefits.

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The mycorrhiza-dependent defensin MtDefMd1 of Medicago truncatula acts during the late restructuring stages of arbuscule-containing cells

The mycorrhiza-dependent defensin MtDefMd1 of Medicago truncatula acts during the late restructuring stages of arbuscule-containing cells | Plant-Microbe Symbiosis | Scoop.it
Different symbiotic and pathogenic plant-microbe interactions involve the production of cysteine-rich antimicrobial defensins. In Medicago truncatula, the expression of four MtDefMd genes, encoding arbuscular mycorrhiza-dependent defensins containing an N-terminal signal peptide and exhibiting some differences to non-symbiotic defensins, raised over the time of fungal colonization. Whereas the MtDefMd1 and MtDefMd2 promoters were inactive in cells containing young arbuscules, cells with fully developed arbuscules displayed different levels of promoter activities, indicating an up-regulation towards later stages of arbuscule formation. MtDefMd1 and MtDefMd2 expression was absent or strongly down-regulated in mycorrhized ram1-1 and pt4-2 mutants, known for defects in arbuscule branching or premature arbuscule degeneration, respectively. A ~97% knock-down of MtDefMd1/MtDefMd2 expression did not significantly affect arbuscule size. Although overexpression of MtDefMd1 in arbuscule-containing cells led to an up-regulation of MtRam1, encoding a key transcriptional regulator of arbuscule formation, no morphological changes were evident. Co-localization of an MtDefMd1-mGFP6 fusion with additional, subcellular markers revealed that this defensin is associated with arbuscules in later stages of their life-cycle. MtDefMd1-mGFP6 was detected in cells with older arbuscules about to collapse, and ultimately in vacuolar compartments. Comparisons with mycorrhized roots expressing a tonoplast marker indicated that MtDefMd1 acts during late restructuring processes of arbuscule-containing cells, upon their transition into a post-symbiotic state.

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Out of Water: The Origin and Early Diversification of Plant R-Genes

During plant-pathogen interactions, plants use intracellular proteins with nucleotide-binding site and leucine-rich repeat (NBS-LRR) domains to detect pathogens. NBS-LRR proteins represent a major class of plant disease resistance genes (R-genes). Whereas R-genes have been well characterized in angiosperms, little is known about their origin and early diversification. Here we perform comprehensive evolutionary analyses of R-genes in plants and report the identification of R-genes in basal-branching streptophytes, including charophytes, liverworts, and mosses. Phylogenetic analyses suggest that plant R-genes originated in charophytes and R-proteins diversified into TIR-NBS-LRR proteins (TNLs) and non-TIR-NBS-LRR proteins (nTNLs) in charophytes. Moreover, we show that plant R-proteins evolved in a modular fashion through frequent gain or loss of protein domains. Most of the R-genes in basal-branching streptophytes underwent adaptive evolution, indicating an ancient involvement of R-genes in plant-pathogen interactions. Our findings provide novel insights into the origin and evolution of R-genes and the mechanisms underlying colonization of terrestrial environments by plants.

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