MycorWeb Plant-Microbe Interactions
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Genomics: Keen insights from quinoa

Genomics: Keen insights from quinoa | MycorWeb Plant-Microbe Interactions | Scoop.it
In 2006, one of us estimated that, given ongoing technological advances, 200 domesticated plants would be sequenced within 14 years1. Genomics has already outstripped this prediction, with most major crop plants, domesticated animals and model organisms having now been sequenced. Nonetheless, the genomes of many organisms that are valuable to local communities and have potentially high salience to a world challenged by issues of food security remain to be tackled. One example of such an organism is the Andean crop quinoa (Chenopodium quinoa). In a paper online in Nature, Jarvis et al.2 report a high-quality genome sequence for this species.

Archaeological evidence3 indicates that quinoa was domesticated some 7,000 years ago in the high plateau around Lake Titicaca in the Andes (Fig. 1), becoming a major food crop for Andean civilizations that preceded the Inca3, 4. Quinoa was prized for its nutritional qualities and adaptability to diverse environments, growing at an exceptional range of altitudes (from sea level to 4 kilometres above it), temperatures (from −8 °C to 38 °C), humidities and soil conditions5. By the mid-twentieth century, quinoa had fallen out of fashion, being cultivated mainly by isolated native communities in the Andean highlands. It wasn't until the 1970s that the plant's nutritional and commercial potential began to be more widely appreciated6, but increased scientific input into breeding programmes will be needed if the full potential of this crop is to be realized.
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Adaptive and plastic responses of Quercus petraea populations to climate across Europe

Adaptive and plastic responses of Quercus petraea populations to climate across Europe | MycorWeb Plant-Microbe Interactions | Scoop.it
How temperate forests will respond to climate change is uncertain; projections range from severe decline to increased growth. We conducted field tests of sessile oak (Quercus petraea), a widespread keystone European forest tree species, including more than 150 000 trees sourced from 116 geographically diverse populations. The tests were planted on 23 field sites in six European countries, in order to expose them to a wide range of climates, including sites reflecting future warmer and drier climates. By assessing tree height and survival, our objectives were twofold: (i) to identify the source of differential population responses to climate (genetic differentiation due to past divergent climatic selection vs. plastic responses to ongoing climate change) and (ii) to explore which climatic variables (temperature or precipitation) trigger the population responses. Tree growth and survival were modeled for contemporary climate and then projected using data from four regional climate models for years 2071–2100, using two greenhouse gas concentration trajectory scenarios each. Overall, results indicated a moderate response of tree height and survival to climate variation, with changes in dryness (either annual or during the growing season) explaining the major part of the response. While, on average, populations exhibited local adaptation, there was significant clinal population differentiation for height growth with winter temperature at the site of origin. The most moderate climate model (HIRHAM5-EC; rcp4.5) predicted minor decreases in height and survival, while the most extreme model (CCLM4-GEM2-ES; rcp8.5) predicted large decreases in survival and growth for southern and southeastern edge populations (Hungary and Turkey). Other nonmarginal populations with continental climates were predicted to be severely and negatively affected (Bercé, France), while populations at the contemporary northern limit (colder and humid maritime regions; Denmark and Norway) will probably not show large changes in growth and survival in response to climate change.
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Enseigner la théorie de l'évolution en France : aller au-delà des voeux pieux

Enseigner la théorie de l'évolution en France : aller au-delà des voeux pieux | MycorWeb Plant-Microbe Interactions | Scoop.it
Avec 1,5 km, la Rue Lamarck est parmi les plus longues du 18ᵉ arrondissement ; la rue Darwin, voisine, ne mesure que… 86 m de long. Cette écart symbolise le lien particulier de la France à l’évolution. Adhérent très tôt aux théories de l’évolutionniste Lamarck (inventeur du concept de transformisme, qui établit que le monde biologique a changé), notre pays a assimilé avec réticences, puis avec lenteur, les mécanismes qui sont à l’origine de ce changement biologique : la sélection naturelle, proposée par Darwin. D’autres mécanismes relatifs à l’évolution seront découverts ensuite.

À la fin du XIXᵉ siècle, le poids d’un Pasteur estompe l’impact de Darwin : poussée à l’extrême, la théorie darwinienne suggère qu’à l’origine, une génération spontanée « initiale » a pu engendrer la vie. Cette apparition sans créateur a indisposé pas mal d’églises. Pasteur, conservateur et clérical, avait, lui, affirmé qu’il n’y avait pas de génération spontanée : il n’appréciait guère le darwinisme et ne mentionna jamais Darwin dans ses textes. Pasteur accepte un monde créé, puisque la vie ne peut apparaître spontanément. Ainsi s’ébaucha une biologie française sans darwinisme.
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Did trees grow up to the light, up to the wind, or down to the water? How modern high productivity colors perception of early plant evolution

Did trees grow up to the light, up to the wind, or down to the water? How modern high productivity colors perception of early plant evolution | MycorWeb Plant-Microbe Interactions | Scoop.it
Flowering plants can be far more productive than other living land plants. Evidence is reviewed that productivity would have been uniformly lower and less CO2-responsive before angiosperm evolution, particularly during the early evolution of vascular plants and forests in the Devonian and Carboniferous. This introduces important challenges because paleoecological interpretations have been rooted in understanding of modern angiosperm-dominated ecosystems. One key example is tree evolution: although often thought to reflect competition for light, light limitation is unlikely for plants with such low photosynthetic potential. Instead, during this early evolution, the capacities of trees for enhanced propagule dispersal, greater leaf area, and deep-rooting access to nutrients and the water table are all deemed more fundamental potential drivers than light.
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Long-distance peptide signaling essential for nutrient homeostasis in plants

Long-distance peptide signaling essential for nutrient homeostasis in plants | MycorWeb Plant-Microbe Interactions | Scoop.it

Highlights

• Several secreted peptides act as root-to-shoot long-distance mobile signals.
• Plants employ this long-distance signaling to adapt to fluctuating nutrient status.
• Transpiration may be a driving force for root-to-shoot translocation of peptides.

Organ-to-organ communication is indispensable for higher organisms to maintain homeostasis over their entire life. Recent findings have uncovered that plants, like animals, mediate organ-to-organ communication by long-distance signaling through the vascular system. In particular, xylem-mobile secreted peptides have attracted much attention as root-to-shoot long-distance signaling molecules in response to fluctuating environmental nutrient status. Several leguminous CLE peptides induced by rhizobial inoculation act as ‘satiety’ signals in long-distance negative feedback of nodule formation. By contrast, Arabidopsis CEP family peptides induced by local nitrogen (N)-starvation behave as systemic ‘hunger’ signals to promote compensatory N acquisition in other parts of the roots. Xylem sap peptidomics also implies the presence of still uncharacterized long-distance signaling peptides. This review highlights the current understanding of and new insights into the mechanisms and functions of root-to-shoot long-distance peptide signaling during environmental responses.


Via Christophe Jacquet
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Rescooped by Francis Martin from Plants & Evolution
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Physiological responses and gene co-expression network of mycorrhizal roots under K+ deprivation

Arbuscular mycorrhizal (AM) associations enhance the phosphorous and nitrogen nutrition of host plants, but little is known about their role in potassium (K+) nutrition. Medicago truncatula plants were co-cultured with the AM fungus Rhizophagus irregularis under high and low K+ regimes for six weeks. We determined how K+ deprivation affects plant development, mineral acquisition, and how these negative effects are tempered by the AM colonization. The transcriptional response of AM roots under K+ deficiency was analyzed by whole genome RNA-seq. K+ deprivation decreased root biomass, external K+ uptake, and modulated oxidative stress gene expression in M. truncatula roots. AM colonization induced specific transcriptional responses to K+ deprivation that seem to temper these negative effects. A gene network analysis revealed putative key regulators of these responses. This study confirmed that AM associations provide some tolerance to K+ deprivation to host plants, revealed that AM symbiosis modulates the expression of specific root genes to cope with this nutrient stress, and identified putative regulators participating in these tolerance mechanisms.

Via Pierre-Marc Delaux
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Evolutionary history of versatile-lipases from Agaricales through reconstruction of ancestral structures

Evolutionary history of versatile-lipases from Agaricales through reconstruction of ancestral structures | MycorWeb Plant-Microbe Interactions | Scoop.it

Background

Fungal “Versatile carboxylic ester hydrolases” are enzymes with great biotechnological interest. Here we carried out a bioinformatic screening to find these proteins in genomes from Agaricales, by means of searching for conserved motifs, sequence and phylogenetic analysis, and three-dimensional modeling. Moreover, we reconstructed the molecular evolution of these enzymes along the time by inferring and analyzing the sequence of ancestral intermediate forms.


Results

The properties of the ancestral candidates are discussed on the basis of their three-dimensional structural models, the hydrophobicity of the lid, and the substrate binding intramolecular tunnel, revealing all of them featured properties of these enzymes. The evolutionary history of the putative lipases revealed an increase on the length and hydrophobicity of the lid region, as well as in the size of the substrate binding pocket, during evolution time. These facts suggest the enzymes’ specialization towards certain substrates and their subsequent loss of promiscuity.


Conclusions
These results bring to light the presence of different pools of lipases in fungi with different habitats and life styles. Despite the consistency of the data gathered from reconstruction of ancestral sequences, the heterologous expression of some of these candidates would be essential to corroborate enzymes’ activities.

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Effects of jasmonic acid signalling on the wheat microbiome differ between body sites

Effects of jasmonic acid signalling on the wheat microbiome differ between body sites | MycorWeb Plant-Microbe Interactions | Scoop.it

Jasmonic acid (JA) signalling helps plants to defend themselves against necrotrophic pathogens and herbivorous insects and has been shown to influence the root microbiome of Arabidopsis thaliana. In this study, we determined whether JA signalling influences the diversity and functioning of the wheat (Triticum aestivum) microbiome and whether these effects are specific to particular parts of the plant. Activation of the JA pathway was achieved via exogenous application of methyl jasmonate and was confirmed by significant increases in the abundance of 10 JA-signalling-related gene transcripts. Phylogenetic marker gene sequencing revealed that JA signalling reduced the diversity and changed the composition of root endophytic but not shoot endophytic or rhizosphere bacterial communities. The total enzymatic activity and substrate utilisation profiles of rhizosphere bacterial communities were not affected by JA signalling. Our findings indicate that the effects of JA signalling on the wheat microbiome are specific to individual plant compartments.


Via Stéphane Hacquard, Ryohei Thomas Nakano, Jim Alfano
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Mutualistic mimicry enhances species diversification through spatial segregation and extension of the ecological niche space

Mutualistic mimicry enhances species diversification through spatial segregation and extension of the ecological niche space | MycorWeb Plant-Microbe Interactions | Scoop.it

Species richness varies among clades, yet the drivers of diversification creating this variation remain poorly understood. While abiotic factors likely drive some of the variation in species richness, ecological interactions may also contribute. Here, we examine one class of potential contributors to species richness variation that is particularly poorly understood: mutualistic interactions. We aim to elucidate large-scale patterns of diversification mediated by mutualistic interactions using a spatially-explicit population-based model. We focus on mutualistic Müllerian mimicry between conspicuous toxic prey species, where convergence in colour patterns emerges from predators' learning process. To investigate the effects of Müllerian mimicry on species diversification, we assume that some speciation events stem from shifts in ecological niches, and can also be associated with shift in mimetic colour pattern. Through the emergence of spatial mosaics of mimetic colour patterns, Müllerian mimicry constrains the geographical distribution of species and allows different species with similar ecological niches to exist simultaneously in different regions. Müllerian mimicry and the resulting spatial segregation of mimetic colour patterns thus generate more balanced phylogenetic trees and increase overall species diversity. Our study sheds light on complex effects of Müllerian mimicry on ecological, spatial and phylogenetic diversification.


Via Jonathan Plett
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Recent breakthroughs in metabolomics promise to reveal the cryptic chemical traits that mediate plant community composition, character evolution and lineage diversification

Recent breakthroughs in metabolomics promise to reveal the cryptic chemical traits that mediate plant community composition, character evolution and lineage diversification | MycorWeb Plant-Microbe Interactions | Scoop.it
Much of our understanding of the mechanisms by which biotic interactions shape plant communities has been constrained by the methods available to study the diverse secondary chemistry that defines plant relationships with other organisms. Recent innovations in analytical chemistry and bioinformatics promise to reveal the cryptic chemical traits that mediate plant ecology and evolution by facilitating simultaneous structural comparisons of hundreds of unknown molecules to each other and to libraries of known compounds. Here, I explore the potential for mass spectrometry and nuclear magnetic resonance metabolomics to enable unprecedented tests of seminal, but largely untested hypotheses that propose a fundamental role for plant chemical defenses against herbivores and pathogens in the evolutionary origins and ecological coexistence of plant species diversity.
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A chemical genetic roadmap to improved tomato flavor

A chemical genetic roadmap to improved tomato flavor | MycorWeb Plant-Microbe Interactions | Scoop.it
Modern commercial tomato varieties are substantially less flavorful than heirloom varieties. To understand and ultimately correct this deficiency, we quantified flavor-associated chemicals in 398 modern, heirloom, and wild accessions. A subset of these accessions was evaluated in consumer panels, identifying the chemicals that made the most important contributions to flavor and consumer liking. We found that modern commercial varieties contain significantly lower amounts of many of these important flavor chemicals than older varieties. Whole-genome sequencing and a genome-wide association study permitted identification of genetic loci that affect most of the target flavor chemicals, including sugars, acids, and volatiles. Together, these results provide an understanding of the flavor deficiencies in modern commercial varieties and the information necessary for the recovery of good flavor through molecular breeding.
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Identification of two mutations that cause defects in the ligninolytic system through an efficient forward genetics in the white-rot agaricomycete Pleurotus ostreatus

Identification of two mutations that cause defects in the ligninolytic system through an efficient forward genetics in the white-rot agaricomycete Pleurotus ostreatus | MycorWeb Plant-Microbe Interactions | Scoop.it
White-rot fungi play an important role in the global carbon cycle because they are the species that almost exclusively biodegrade wood lignin in nature. Lignin peroxidases (LiPs), manganese peroxidases (MnPs) and versatile peroxidases (VPs) are considered key players in the ligninolytic system. Apart from LiPs, MnPs and VPs, however, only few other factors involved in the ligninolytic system have been investigated using molecular genetics, implying the existence of unidentified elements. By combining classical genetic techniques with next-generation sequencing technology, they successfully showed an efficient forward genetics approach to identify mutations causing defects in the ligninolytic system of the white-rot fungus Pleurotus ostreatus. In this study, they identified two genes – chd1 and wtr1 – mutations in which cause an almost complete loss of Mn2+-dependent peroxidase activity. The chd1 gene encodes a putative chromatin modifier, and wtr1 encodes an agaricomycete-specific protein with a putative DNA-binding domain. The chd1-1 mutation and targeted disruption of wtr1 hamper the ability of P. ostreatus to biodegrade wood lignin. Examination of the effects of the aforementioned mutation and disruption on the expression of certain MnP/VP genes suggests that a complex mechanism underlies the ligninolytic system in P. ostreatus.
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Lyme : collectionnons les tiques pour aider les chercheurs !

Lyme : collectionnons les tiques pour aider les chercheurs ! | MycorWeb Plant-Microbe Interactions | Scoop.it
Peut-être avez-vous déjà compté les papillons dans votre jardin à l’intention du Museum national d’histoire naturelle ? Alors vous serez sans doute ravi de signaler bientôt vos piqûres de tiques ou celles de votre chien aux scientifiques de l’Institut national de recherche agronomique (Inra). Et d’aider, ainsi, à vaincre la maladie de Lyme.

Cette pathologie et d’autres transmises aux humains par les tiques sont devenues au fil des ans un problème important de santé publique. Or on en sait encore trop peu sur ces parasites et les agents infectieux qu’ils transportent. C’est pourquoi plusieurs équipes de scientifiques se sont associées pour demander à tous les Français volontaires de s’impliquer dans l’effort de recherche en cours. Ce projet a été baptisé Citicks, « ci » pour citoyens, et « ticks », pour tiques, en anglais.
Les Français se prennent au jeu des sciences participatives

En 2006, certains de nos compatriotes se postaient déjà sur leurs balcons pour noter combien ils voyaient passer de papillons « citrons » ou « petite tortue ». En dix ans, les Français se sont pris au jeu des sciences participatives. Ce mouvement, associant citoyens et chercheurs, permet d’accélérer l’acquisition des connaissances. Le projet Citicks s’est déjà doté d’un compte Twitter. Et notre équipe de scientifiques espère que le dispositif sera prêt cet automne pour que les citoyens puissent à leur tour entrer dans la danse.
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Soil networks become more connected and take up more carbon as nature restoration progresses

Soil networks become more connected and take up more carbon as nature restoration progresses | MycorWeb Plant-Microbe Interactions | Scoop.it
Soil organisms have an important role in aboveground community dynamics and ecosystem functioning in terrestrial ecosystems. However, most studies have considered soil biota as a black box or focussed on specific groups, whereas little is known about entire soil networks. Here we show that during the course of nature restoration on abandoned arable land a compositional shift in soil biota, preceded by tightening of the belowground networks, corresponds with enhanced efficiency of carbon uptake. In mid- and long-term abandoned field soil, carbon uptake by fungi increases without an increase in fungal biomass or shift in bacterial-to-fungal ratio. The implication of our findings is that during nature restoration the efficiency of nutrient cycling and carbon uptake can increase by a shift in fungal composition and/or fungal activity. Therefore, we propose that relationships between soil food web structure and carbon cycling in soils need to be reconsidered.
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Résilience du chêne sessile aux variations climatiques en Europe

Résilience du chêne sessile aux variations climatiques en Europe | MycorWeb Plant-Microbe Interactions | Scoop.it
Pour étudier les réponses du chêne sessile aux variations climatiques, les chercheurs de l’Inra, en collaboration avec l’ONF et des partenaires européens, ont analysé les données de survie et de croissance de l’espèce dans un réseau de plantations expérimentales installées il y a 30 ans dans plusieurs pays européens, depuis l’Angleterre et la Scandinavie jusqu’en Turquie. Des populations issues de 116 origines géographiques avaient été transférées par plantation dans 23 forêts. Parmi ces transferts de populations, certains reproduisent spatialement des variations climatiques analogues à celles annoncées par les prédictions du GIEC1. Ces plantations fournissent ainsi des éléments importants relatifs aux réponses futures du chêne sessile au changement climatique.

Les résultats montrent que, globalement, l’espèce manifeste une faible sensibilité aux variations climatiques. Le facteur qui génère les variations les plus importantes est le manque d’eau. On note par contre des réponses différentielles des origines géographiques : les populations venant de climats plus chauds ont une croissance inférieure à celle provenant de climats plus froids, montrant que le climat d’origine des populations a contribué à leur différenciation génétique perceptible aujourd’hui.
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The Comparison of Expressed Candidate Secreted Proteins from Two Arbuscular Mycorrhizal Fungi Unravels Common and Specific Molecular Tools to Invade Different Host Plants

The Comparison of Expressed Candidate Secreted Proteins from Two Arbuscular Mycorrhizal Fungi Unravels Common and Specific Molecular Tools to Invade Different Host Plants | MycorWeb Plant-Microbe Interactions | Scoop.it
Arbuscular mycorrhizal fungi (AMF), belonging to the fungal phylum Glomeromycota, form mutualistic symbioses with roots of almost 80% of land plants. The release of genomic data from the ubiquitous AMF Rhizophagus irregularis revealed that this species possesses a large set of putative secreted proteins (RiSPs) that could be of major importance for establishing the symbiosis. In the present study, we aimed to identify SPs involved in the establishment of AM symbiosis based on comparative gene expression analyses. We first curated the secretome of the R. irregularis DAOM 197198 strain based on two available genomic assemblies. Then we analyzed the expression patterns of the putative RiSPs obtained from the fungus in symbiotic association with three phylogenetically distant host plants—a monocot, a dicot and a liverwort—in comparison with non-symbiotic stages. We found that 33 out of 84 RiSPs induced in planta were commonly up-regulated in these three hosts. Most of these common RiSPs are small proteins of unknown function that may represent putative host non-specific effector proteins. We further investigated the expressed secretome of Gigaspora rosea, an AM fungal species phylogenetically distant from R. irregularis. G. rosea also presents original symbiotic features, a narrower host spectrum and a restrictive geographic distribution compared to R. irregularis. Interestingly, when analyzing up-regulated G. rosea SPs (GrSPs) in different hosts, a higher ratio of host-specific GrSPs was found compared to RiSPs. Such difference of expression patterns may mirror the restrained host spectrum of G. rosea compared to R. irregularis. Finally, we identified a set of conserved SPs, commonly up-regulated by both fungi in all hosts tested, that could correspond to common keys of AMF to colonize host plants. Our data thus highlight the specificities of two distant AM fungi and help in understanding their conserved and specific strategies to invade different hosts.
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Rescooped by Francis Martin from Plant pathogens and pests
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LOCALIZER: subcellular localization prediction of plant and effector proteins in the plant cell

LOCALIZER: subcellular localization prediction of plant and effector proteins in the plant cell | MycorWeb Plant-Microbe Interactions | Scoop.it
Pathogens are able to deliver effector proteins into plant cells to enable infection. Some effectors have been found to enter subcellular compartments by mimicking host targeting sequences. Although many computational methods exist to predict plant protein subcellular localization, they perform poorly for effectors. We introduce LOCALIZER for predicting plant and effector protein localization to chloroplasts, mitochondria, and nuclei. LOCALIZER shows greater prediction accuracy for chloroplast and mitochondrial targeting compared to other methods for 652 plant proteins. For 108 eukaryotic effectors, LOCALIZER outperforms other methods and predicts a previously unrecognized chloroplast transit peptide for the ToxA effector, which we show translocates into tobacco chloroplasts. Secretome-wide predictions and confocal microscopy reveal that rust fungi might have evolved multiple effectors that target chloroplasts or nuclei. LOCALIZER is the first method for predicting effector localisation in plants and is a valuable tool for prioritizing effector candidates for functional investigations. LOCALIZER is available at http://localizer.csiro.au/.


Via Steve Marek, Christophe Jacquet
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The Identification of Phytohormone Receptor Homologs in Early Diverging Fungi Suggests a Role for Plant Sensing in Land Colonization by Fungi

The Identification of Phytohormone Receptor Homologs in Early Diverging Fungi Suggests a Role for Plant Sensing in Land Colonization by Fungi | MycorWeb Plant-Microbe Interactions | Scoop.it
Histidine kinases (HKs) are among the most prominent sensing proteins studied in the kingdom Fungi. Their distribution and biological functions in early diverging fungi (EDF), however, remain elusive. We have taken advantage of recent genomic resources to elucidate whether relationships between the occurrence of specific HKs in some EDF and their respective habitat/lifestyle could be established. This led to the unexpected discovery of fungal HKs that share a high degree of similarity with receptors for plant hormones (ethylene and cytokinin). Importantly, these phytohormone receptor homologs are found not only in EDF that behave as plant root symbionts or endophytes but also in EDF species that colonize decaying plant material. We hypothesize that these particular sensing proteins promoted the interaction of EDF with plants, leading to the conquest of land by these ancestral fungi.

Via Christophe Jacquet
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Rescooped by Francis Martin from Plant Sciences
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RNA Interference Between Kingdoms | The Scientist Magazine

RNA Interference Between Kingdoms | The Scientist Magazine | MycorWeb Plant-Microbe Interactions | Scoop.it
Plants and fungi can use conserved RNA interference machinery to regulate each other’s gene expression—and scientists think they can make use of this phenomenon to create a new generation of pesticides.

Via Steve Marek, Saclay Plant Sciences
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OsCERK1-mediated chitin perception and immune signaling requires Receptor-like Cytoplasmic Kinase 185 to activate a MAPK cascade in rice

OsCERK1-mediated chitin perception and immune signaling requires Receptor-like Cytoplasmic Kinase 185 to activate a MAPK cascade in rice | MycorWeb Plant-Microbe Interactions | Scoop.it
Conserved pathogen-associated molecular patterns (PAMPs), such as chitin, are perceived by pattern recognition receptors (PRRs) located at the host cell surface and trigger rapid activation of mitogen-activated protein kinase (MAPK) cascades, which is required for plant resistance to pathogens. However, the direct link from PAMP perception to MAPK activation in plants is elusive. Here, we found that the PRR-associated receptor-like cytoplasmic kinase Oryza sativa RLCK185 transmits immune signaling from the PAMP receptor OsCERK1 to a MAPK signaling cascade through interaction with a MAPK kinase kinase, OsMAPKKKε, which is the initial kinase of the MAPK cascade. OsRLCK185 interacts with and phosphorylates the C-terminal regulatory domain of OsMAPKKKε. Coexpression of phosphomimetic OsRLCK185 and OsMAPKKKε activates MAPK3/6 phosphorylation in Nicotiana benthamiana leaves. OsMAPKKKε interacts with and phosphorylates OsMKK4, a key MAPK kinase that transduces the chitin signal. OsMAPKKKε overexpression increases chitin-induced MAPK3/6 activation. OsMAPKKKε knockdown compromises chitin-induced MAPK3/6 activation and resistance to rice blast fungus. These findings suggest a phospho-signaling pathway from cell surface chitin perception to intracellular activation of a MAPK cascade in rice.

Via Christophe Jacquet, Jim Alfano
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Two cultivated legume plants reveal the enrichment process of the microbiome in the rhizocompartments

Two cultivated legume plants reveal the enrichment process of the microbiome in the rhizocompartments | MycorWeb Plant-Microbe Interactions | Scoop.it

The microbiomes of rhizocompartments (nodule endophytes, root endophytes, rhizosphere and root zone) in soybean and alfalfa were analyzed using high-throughput sequencing to investigate the interactions among legume species, microorganisms and soil types. A clear hierarchical filtration of microbiota by plants was observed in the four rhizocompartments—the nodule endosphere, root endosphere, rhizosphere and root zone—as demonstrated by significant variations in the composition of the microbial community in the different compartments. The rhizosphere and root zone microbial communities were largely influenced by soil type, and the nodule and root endophytes were primarily determined by plant species. Diverse microbes inhabited the root nodule endosphere, and the corresponding dominant symbiotic rhizobia belonged to Ensifer for alfalfa and Ensifer-Bradyrhizobium for soybean. The non-symbiotic nodule endophytes were mainly Proteobacteria, Actinobacteria, Firmicutes and Bacteroidetes. The variation in root microbial communities was also affected by the plant growth stage. In summary, this study demonstrated that the enrichment process of nodule endophytes follows a hierarchical filtration and that the bacterial communities in nodule endophytes vary according to the plant species.The microbiomes of rhizocompartments (nodule endophytes, root endophytes, rhizosphere and root zone) in soybean and alfalfa were analyzed using high‐throughput sequencing to investigate th


Via Stéphane Hacquard
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Host autophagosomes are diverted to a plant-pathogen interface

Host autophagosomes are diverted to a plant-pathogen interface | MycorWeb Plant-Microbe Interactions | Scoop.it
Filamentous plant pathogens and symbionts invade their host cells but remain enveloped by host-derived membranes. The mechanisms underlying the biogenesis and functions of these host-microbe interfaces are poorly understood. Recently, we showed that PexRD54, an effector from the Irish potato famine pathogen Phytophthora infestans, binds host protein ATG8CL to stimulate autophagosome formation and deplete the selective autophagy receptor Joka2 from ATG8CL complexes. Here, we show that during P. infestans infection, ATG8CL autophagosomes are diverted to the pathogen interface. Our findings are consistent with the view that the pathogen coopts host selective autophagy for its own benefit.

Via Christophe Jacquet
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Distinct regions of the Phytophthora essential effector Avh238 determine its function in cell death activation and plant immunity suppression

Distinct regions of the Phytophthora essential effector Avh238 determine its function in cell death activation and plant immunity suppression | MycorWeb Plant-Microbe Interactions | Scoop.it
Phytophthora pathogens secrete effectors to manipulate host innate immunity, thus facilitating infection. Among the RXLR effectors highly induced during Phytophthora sojae infection, Avh238 not only contributes to pathogen virulence but also triggers plant cell death. However, the detailed molecular basis of Avh238 functions remains largely unknown. We mapped the regions responsible for Avh238 functions in pathogen virulence and plant cell death induction using a strategy that combines investigation of natural variation and large-scale mutagenesis assays. The correlation between cellular localization and Avh238 functions was also evaluated. We found that the 79th residue (histidine or leucine) of Avh238 determined its cell death-inducing activity, and that the 53 amino acids in its C-terminal region are responsible for promoting Phytophthora infection. Transient expression of Avh238 in Nicotiana benthamiana revealed that nuclear localization is essential for triggering cell death, while Avh238-mediated suppression of INF1-triggered cell death requires cytoplasmic localization. Our results demonstrate that a representative example of an essential Phytophthora RXLR effector can evolve to escape recognition by the host by mutating one nucleotide site, and can also retain plant immunosuppressive activity to enhance pathogen virulence in planta.
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Functional PTB phosphate transporters are present in streptophyte algae and early diverging land plants

Two inorganic phosphate (Pi) uptake mechanisms operate in streptophytes and chlorophytes, the two lineages of green plants. PHOSPHATE TRANSPORTER B (PTB) proteins are hypothesized to be the Na+/Pi symporters catalysing Pi uptake in chlorophytes, whereas PHOSPHATE TRANSPORTER 1 (PHT1) proteins are the H+/Pi symporters that carry out Pi uptake in angiosperms. PHT1 proteins are present in all streptophyte lineages. However, Pi uptake in streptophyte algae and marine angiosperms requires Na+ influx, suggesting that Na+/Pi symporters also function in some streptophytes. We tested the hypothesis that Na+/Pi symporters exist in streptophytes. We identified PTB sequences in streptophyte genomes. Core PTB proteins are present at the plasma membrane of the liverwort Marchantia polymorpha. The expression of M. polymorpha core PTB proteins in the Saccharomyces cerevisiae pho2 mutant defective in high-affinity Pi transport rescues growth in low-Pi environments. Moreover, levels of core PTB mRNAs of M. polymorpha and the streptophyte alga Coleochaete nitellarum are higher in low-Pi than in Pi-replete conditions, consistent with a role in Pi uptake from the environment. We conclude that land plants inherited two Pi uptake mechanisms – mediated by the PTB and PHT1 proteins, respectively – from their streptophyte algal ancestor. Both systems operate in parallel in extant early diverging land plants.


Via Pierre-Marc Delaux
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Scooped by Francis Martin
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Multispecies genetic structure and hybridization in the Betula genus across Eurasia

Multispecies genetic structure and hybridization in the Betula genus across Eurasia | MycorWeb Plant-Microbe Interactions | Scoop.it
Boreal and cool temperate forests are the major land cover of northern Eurasia, and information about continental-scale genetic structure and past demographic history of forest species is important from an evolutionary perspective and has conservation implications. However, although many population genetic studies of forest tree species have been conducted in Europe or Eastern Asia, continental-scale genetic structure and past demographic history remain poorly known. Here, we focus on the birch genus Betula, which is commonly distributed in boreal and cool temperate forests, and examine 129 populations of two tetraploid and four diploid species collected from Iceland to Japan. All individuals were genotyped at seven to 18 nuclear simple sequence repeats (nSSRs). Pairwise inline image among the six species ranged from 0.285 to 0.903, and genetic differentiation among them was clear. structure analysis suggested that Betula pubescens is an allotetraploid and one of the parental species was Betula pendula. In both species pairs of B. pendula and B. plathyphylla, and B. pubescens and B. ermanii, genetic diversity was highest in central Siberia. A hybrid zone was detected around Lake Baikal for eastern and western species pairs regardless of ploidy level. Approximate Bayesian computation suggested that the divergence of B. pendula and B. platyphylla occurred around the beginning of the last ice age (36 300 years BP, 95% CI: 15 330–92 700) and hybridization between them was inferred to have occurred after the last glacial maximum (1614 years BP, 95% CI: 561–4710), with B. pendula providing a higher contribution to hybrids.
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