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Rescooped by Francis Martin from Plant-Microbe Symbiosis
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DELLA proteins regulate expression of a subset of AM symbiosis-induced genes in Medicago truncatula

The majority of the vascular flowering plants form symbiotic associations with fungi from the phylum Glomeromycota through which both partners gain access to nutrients, either mineral nutrients in the case of the plant, or carbon, in the case of the fungus 1. The association develops in the roots and requires substantial remodeling of the root cortical cells where branched fungal hyphae called arbuscules are housed in a new membrane-bound apoplastic compartment 2. Nutrient exchange between the symbionts occurs over this interface and its development and maintenance is critical for symbiosis. Previously, we showed that DELLA proteins, which are well known as repressors of gibberellic acid signaling, also regulate development of AM symbiosis and are necessary to enable arbuscule development3. Furthermore, constitutive overexpression of a dominant DELLA protein (della1-Δ18) is sufficient to induce transcripts of several AM symbiosis-induced genes, even in the absence of the fungal symbiont 4. Here we further extend this approach and identify AM symbiosis genes that respond transcriptionally to constitutive expression of a dominant DELLA protein and also genes that do respond to this treatment. Additionally, we demonstrate that DELLAs interact with REQUIRED FOR ARBUSCULE DEVELOPMENT 1 (RAD1) which further extends our knowledge of GRAS factor complexes that have the potential to regulate gene expression during AM symbiosis.

Via Jean-Michel Ané
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Do mycorrhizal fungi drive speciation in Teagueia (Orchidaceae) in the upper Pastaza watershed of Ecuador?

Do mycorrhizal fungi drive speciation in Teagueia (Orchidaceae) in the upper Pastaza watershed of Ecuador? | MycorWeb Plant-Microbe Interactions | Scoop.it
The orchid genus Teagueia Luer (Orchidaceae, subtribe Pleurothallidinae) presents an extraordinary example of recent local evolutionary radiation. In principle, mutualisms might affect the origin of plant species via an effect on speciation. As orchids depend on mycorrhizal fungi for seed germination and early plantlet development we tested whether certain mycorrhizal fungi are acting as drivers of this radiation in Teagueia species. Sampling was carried out near Baños in east Andean Ecuador. Roots were collected from a total of 11 flowering individuals of eight morphospecies (referred to as Teagueia spp). The whole ITS1-5.8S- ITS2 nrDNA region and part of the 28S nrDNA were amplified, cloned and sequenced. Molecular phylogeny of the obtained sequences revealed four phylogenetic species of Tulasnellaceae and one of Atractiellales (Pucciniomycotina, Basidiomycota) associated with Teagueia spp. Tulasnelloid fungi were detected in all samples. Up to three different phylogenetic species of mycobionts were found associated with one Teagueia species. We found that co-occurring Teagueia species share mycobionts. All detected mycobionts had wide geographical distribution. Based on the available evidence we conclude that the extraordinary local radiation of Teagueia is most likely driven by other factors than by mycorrhizal fungi, but that mycorrhiza may be a key factor for the coexistence of so many closely related orchid species.
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Boreal and temperate trees show strong acclimation of respiration to warming :

Boreal and temperate trees show strong acclimation of respiration to warming : | MycorWeb Plant-Microbe Interactions | Scoop.it
Plant respiration results in an annual flux of carbon dioxide (CO2) to the atmosphere that is six times as large as that due to the emissions from fossil fuel burning, so changes in either will impact future climate. As plant respiration responds positively to temperature, a warming world may result in additional respiratory CO2 release, and hence further atmospheric warming1, 2. Plant respiration can acclimate to altered temperatures, however, weakening the positive feedback of plant respiration to rising global air temperature3, 4, 5, 6, 7, but a lack of evidence on long-term (weeks to years) acclimation to climate warming in field settings currently hinders realistic predictions of respiratory release of CO2 under future climatic conditions. Here we demonstrate strong acclimation of leaf respiration to both experimental warming and seasonal temperature variation for juveniles of ten North American tree species growing for several years in forest conditions. Plants grown and measured at 3.4 °C above ambient temperature increased leaf respiration by an average of 5% compared to plants grown and measured at ambient temperature; without acclimation, these increases would have been 23%. Thus, acclimation eliminated 80% of the expected increase in leaf respiration of non-acclimated plants. Acclimation of leaf respiration per degree temperature change was similar for experimental warming and seasonal temperature variation. Moreover, the observed increase in leaf respiration per degree increase in temperature was less than half as large as the average reported for previous studies4, 7, which were conducted largely over shorter time scales in laboratory settings. If such dampening effects of leaf thermal acclimation occur generally, the increase in respiration rates of terrestrial plants in response to climate warming may be less than predicted, and thus may not raise atmospheric CO2 concentrations as much as anticipated.
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Shrinking of forest carbon sink under climate change may be ‘less than anticipated’ - Carbon Brief

Shrinking of forest carbon sink under climate change may be ‘less than anticipated’ - Carbon Brief | MycorWeb Plant-Microbe Interactions | Scoop.it
New study suggests trees can adapt to rising temperatures better than thought. But warmer weather will still affect forests' respiration of carbon dioxide.
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Partitioning of fungal assemblages across different marine habitats

Fungi are a highly diverse group of microbes that fundamentally influence the biogeochemistry of the biosphere, but we currently know little about the diversity and distribution of fungi in aquatic habitats. Here we describe shifts in marine fungal community composition across different marine habitats, using targeted pyrosequencing of the fungal Internal Transcribed Spacer (ITS) region. Our results demonstrate strong partitioning of fungal community composition between estuarine, coastal and oceanic samples, with each habitat hosting discrete communities that are controlled by patterns in salinity, temperature, oxygen and nutrients. Whereas estuarine habitats comprised a significant proportion of fungal groups often found in terrestrial habitats, the open ocean sites were dominated by previously unidentified groups. The patterns observed here indicate that fungi are potentially a significant, although largely overlooked, feature of the ocean's microbiota, but greater efforts to characterize marine species are required before the full ecological and biogeochemical importance of marine fungi can be ascertained.
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Some trees could help fight climate change

Some trees could help fight climate change | MycorWeb Plant-Microbe Interactions | Scoop.it
New finding could tweak models of global carbon emissions
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Small genome of the fungus Escovopsis weberi, a specialized disease agent of ant agriculture

Small genome of the fungus Escovopsis weberi, a specialized disease agent of ant agriculture | MycorWeb Plant-Microbe Interactions | Scoop.it
Many microorganisms with specialized lifestyles have reduced genomes. This is best understood in beneficial bacterial symbioses, where partner fidelity facilitates loss of genes necessary for living independently. Specialized microbial pathogens may also exhibit gene loss relative to generalists. Here, we demonstrate that Escovopsis weberi, a fungal parasite of the crops of fungus-growing ants, has a reduced genome in terms of both size and gene content relative to closely related but less specialized fungi. Although primary metabolism genes have been retained, the E. weberi genome is depleted in carbohydrate active enzymes, which is consistent with reliance on a host with these functions. E. weberi has also lost genes considered necessary for sexual reproduction. Contrasting these losses, the genome encodes unique secondary metabolite biosynthesis clusters, some of which include genes that exhibit up-regulated expression during host attack. Thus, the specialized nature of the interaction between Escovopsis and ant agriculture is reflected in the parasite’s genome.
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Getting to know the microbiome

Getting to know the microbiome | MycorWeb Plant-Microbe Interactions | Scoop.it
Human microbiome research is undergoing a renaissance, driven largely by advances in technologies such as ‘next generation’ sequencing that enable a deeper characterization of microbial populations than has ever been possible.
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Analysis of the Phialocephala subalpina Transcriptome during Colonization of Its Host Plant Picea abies

Analysis of the  Phialocephala subalpina  Transcriptome during Colonization of Its Host Plant  Picea abies | MycorWeb Plant-Microbe Interactions | Scoop.it

Background. Phialocephala subalpina belongs to the Phialocephala fortinii s.l.–Acepphala applanata species complex (PAC) forming one of the major groups belonging to the dark septate endophytes (DSE). Depending on the strain, PAC was shown to form neutral to pathogenic associations with its host plant Picea abies. To understand PACs lifestyle we investigated the effect of presence/absence of Picea abies on the transcriptome of strain 6_70_1.


Materials and Methods. PAC strain 6_70_1 was grown in liquid Pachlewski media either induced by its host plant Picea abies or without host plant as a control. Mycelia were harvested in a time course (1, 2, 3, 4, 7, 11, 18 days) with and without induction by the host plant and the fungal transcriptome revealed by Illumina sequencing. Differential gene expression analysis over the time course comparing control and treatment at each time point using the ‘edgeR glm approach’ and a gene enrichment analysis using GO categories were performed.


Results. The three main functional groups within differentially expressed genes were ‘metabolism’, ‘transport’ and ‘cell rescue, defense and virulence’. Additionally, genes especially involved in iron metabolism could be detected by gene set enrichment analysis.


Conclusion. In conclusion, we found PAC strain 6_70_1 to be metabolically very active during colonization of its host plant Picea abies. A major shift in functional groups over the time course of this experiment could not be observed but GO categories which were found to be enriched showed different emphasis depending in the day post induction.

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Iron-eating fungus disintegrates rocks with acid and cellular knives

Iron-eating fungus disintegrates rocks with acid and cellular knives | MycorWeb Plant-Microbe Interactions | Scoop.it
When a hungry fungus anchors itself to an unsuspecting rock, it has a plan of attack. First, it unleashes acid, dissolving surface minerals to get to its food. Then, it releases chemicals that extract that food—in this case, iron. Finally, its fast-growing fungal filaments cut into the remaining rock like a knife, carving deep channels that break up iron-depleted surfaces and expose fresh layers for consumption. Step by step, the fungus Talaromyces flavus knows how to get what it wants. “These organisms, they don’t have a brain, but they’re pretty smart,” says Henry Teng, a geochemist at George Washington University in Washington, D.C.

Microbial geochemists have long known that fungi, bacteria, and other microbes are crucial to weathering, the chemical and physical breakdown of rock. But most experiments have calculated that contribution at arm’s length, mixing microbes and minerals in solution in the lab as an analogy for the watery soil and rock pore spaces in which scientists assumed microbes were doing most of their work. A new study has zoomed in to scrutinize the zone where microbes meet minerals, and showed which chemicals fungi release after they attach to mineral surfaces. It suggests that scientists have underestimated how much fungal weathering goes on at this interface, and that microbes could be more important extractors of nutrients than researchers suspected.
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Oldest ancient-human DNA details dawn of Neanderthals

Oldest ancient-human DNA details dawn of Neanderthals | MycorWeb Plant-Microbe Interactions | Scoop.it
Matthias Meyer has just published the results of what may be the world’s most wasteful genome-sequencing project. In decoding just 0.1% of the genome of the oldest DNA ever recovered from an ancient human, the molecular biologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, threw out enough raw data to map the modern human genome dozens of times over.

But the excess was necessary, because the DNA in the 430,000-year-old bones was degraded and contaminated. Meyer’s feat of recovery has revealed that the remains, from a cavern in northern Spain, represent early Neanderthals — and has pushed back estimates of the time at which the ancient predecessors of humans must have split from those of Neanderthals (M. Meyer et al. Nature http://dx.doi.org/10.1038/nature17405; 2016).
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Shifts in symbiotic associations in plants capable of forming multiple root symbioses across a long-term soil chronosequence

Shifts in symbiotic associations in plants capable of forming multiple root symbioses across a long-term soil chronosequence | MycorWeb Plant-Microbe Interactions | Scoop.it
Changes in soil nutrient availability during long-term ecosystem development influence the relative abundances of plant species with different nutrient-acquisition strategies. These changes in strategies are observed at the community level, but whether they also occur within individual species remains unknown. Plant species forming multiple root symbioses with arbuscular mycorrhizal (AM) fungi, ectomycorrhizal (ECM) fungi, and nitrogen-(N) fixing microorganisms provide valuable model systems to examine edaphic controls on symbioses related to nutrient acquisition, while simultaneously controlling for plant host identity. We grew two co-occurring species, Acacia rostellifera (N2-fixing and dual AM and ECM symbioses) and Melaleuca systena (AM and ECM dual symbioses), in three soils of contrasting ages (c. 0.1, 1, and 120 ka) collected along a long-term dune chronosequence in southwestern Australia. The soils differ in the type and strength of nutrient limitation, with primary productivity being limited by N (0.1 ka), co-limited by N and phosphorus (P) (1 ka), and by P (120 ka). We hypothesized that (i) within-species root colonization shifts from AM to ECM with increasing soil age, and that (ii) nodulation declines with increasing soil age, reflecting the shift from N to P limitation along the chronosequence. In both species, we observed a shift from AM to ECM root colonization with increasing soil age. In addition, nodulation in A. rostellifera declined with increasing soil age, consistent with a shift from N to P limitation. Shifts from AM to ECM root colonization reflect strengthening P limitation and an increasing proportion of total soil P in organic forms in older soils. This might occur because ECM fungi can access organic P via extracellular phosphatases, while AM fungi do not use organic P. Our results show that plants can shift their resource allocation to different root symbionts depending on nutrient availability during ecosystem development.

Via Jean-Michel Ané
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Pedobiologia: Journal of Soil Ecology's curator insight, March 14, 2016 4:16 PM

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Brian Murphy's curator insight, March 15, 2016 5:50 AM

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Network modules and hubs in plant-root fungal biomes

Terrestrial plants host phylogenetically and functionally diverse groups of below-ground microbes, whose community structure controls plant growth/survival in both natural and agricultural ecosystems. Therefore, understanding the processes by which whole root-associated microbiomes are organized is one of the major challenges in ecology and plant science. We here report that diverse root-associated fungi can form highly compartmentalized networks of coexistence within host roots and that the structure of the fungal symbiont communities can be partitioned into semi-discrete types even within a single host plant population. Illumina sequencing of root-associated fungi in a monodominant south beech forest revealed that the network representing symbiont–symbiont co-occurrence patterns was compartmentalized into clear modules, which consisted of diverse functional groups of mycorrhizal and endophytic fungi. Consequently, terminal roots of the plant were colonized by either of the two largest fungal species sets (represented by Oidiodendron or Cenococcum). Thus, species-rich root microbiomes can have alternative community structures, as recently shown in the relationships between human gut microbiome type (i.e. ‘enterotype’) and host individual health. This study also shows an analytical framework for pinpointing network hubs in symbiont–symbiont networks, leading to the working hypothesis that a small number of microbial species organize the overall root–microbiome dynamics.
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Forest resilience; can microbes help combat climate change issues faster than genetic adaptations? - BMC Series blog

Forest resilience; can microbes help combat climate change issues faster than genetic adaptations? - BMC Series blog | MycorWeb Plant-Microbe Interactions | Scoop.it

Today marks the International Day of Forests and so in this guest blog by Armand Séguin, board member for BMC Pant Biology, we focus on one of the major issues facing our forests today: climate change. Can the trees adapt as quickly as the environment is changing? Or is there an alternative that might be able to help…


Could the soil microbiome help combat climate change issues for forests?
Could the soil microbiome help combat climate change issues for forests?
How does climate change affect our forests?

Forests worldwide have played crucial roles in human population developments, traditionally providing wood for construction, heating and natural habitats for fishing and hunting. Forests also have major impacts in economic development in some countries but are now also recognized for their crucial role in ecological services.

Human activities combined with climate change threaten the health of the world’s forests which could impair their associated ecological services. The loss of such services provided by forests has more economical impact than their traditional industrial roles. (Science special issue August 2015).

More than a decade ago the scientific community was asked to provide evidences to clarify two important issues about climate change and the role that forest plays.

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Rescooped by Francis Martin from Plants & Evolution
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Molecular Basis of Lipo-chitooligosaccharide Recognition by the Lysin Motif Receptor-like Kinase LYR3 in Legumes

LYR3 (Lysin Motif (LysM) Receptor-Like Kinase 3) of Medicago truncatula is a high affinity binding protein for symbiotic lipo-chitooligosaccharidic (LCO) signals, produced by Rhizobia bacteria and arbuscular mycorrhizal fungi. This work shows that LYR3 from several other legumes, but not from two Lupinus species which are incapable of forming the mycorrhizal symbiosis, bind LCOs with high affinity and discriminate them from chitooligosaccharides (COs). The biodiversity of these proteins and the lack of binding to the Lupinus proteins were used to identify features required for high affinity LCO binding. Swapping experiments between each of the three LysMs of the extracellular domain of the M. truncatula and Lupinus angustifolius LYR3 proteins revealed the crucial role of the third LysM in LCO binding. Site directed mutagenesis identified a Tyr residue, highly conserved in all the LYR3 LCO-binding proteins, which is essential for high-affinity binding. Molecular modeling suggests that it may be part of a hydrophobic tunnel able to accommodate the LCO acyl chain. The lack of conservation of these features in the binding site of plant LysM proteins binding COs, provides a mechanistic explanation of how LCO recognition might differ from CO perception by structurally-related LysM receptors.

Via Pierre-Marc Delaux
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Fungi are at the root of tropical forest diversity -- or lack thereof, study finds

Fungi are at the root of tropical forest diversity -- or lack thereof, study finds | MycorWeb Plant-Microbe Interactions | Scoop.it
The types of beneficial fungi that associate with tree roots can alter the fate of a patch of tropical forest, boosting plant diversity or, conversely, giving one tree species a distinct advantage over many others, researchers report.

Their study, reported in the journal Ecology Letters, sought to explain a baffling phenomenon in some tropical forests: Small patches of "monodominant forest," where one species makes up more than 60 percent of the trees, form islands of low diversity in the otherwise highly diverse tropical forest growing all around them.

The new study focused on mountain forests in Panama that harbor hundreds of tree species, but which include small patches dominated by the tree species Oreomunnea mexicana.

Via Jean-Michel Ané
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The phosphate transporters LjPT4 and MtPT4 mediate early root responses to phosphate status in non mycorrhizal roots

The phosphate transporters LjPT4 and MtPT4 mediate early root responses to phosphate status in non mycorrhizal roots | MycorWeb Plant-Microbe Interactions | Scoop.it
Arbuscular mycorrhizal (AM) symbiosis improves host plant phosphorous (P) status and elicits the expression of AM-inducible phosphate transporters (PTs) in arbuscule-containing cells, where they control arbuscule morphogenesis and P release. We confirmed such functions for LjPT4 in mycorrhizal Lotus japonicus. Promoter-GUS experiments showed LjPT4 transcription not only in arbusculated cells, but also in root tips, in the absence of the fungus: here LjPT4 transcription profile depended on the phosphate level. In addition, quantitative RT-PCR confirmed the expression of Lotus and Medicago truncatula PT4 in the tips of non-mycorrhizal roots. Starting from these observations, we hypothesized that AM-inducible PTs may have a regulatory role in plant development, irrespective of the fungal presence. Firstly, we focused on root development responses to different phosphate treatments in both plants demonstrating that phosphate starvation induced a higher number of lateral roots. By contrast, Lotus PT4i plants and Medicago mtpt4 mutants did not show any differential response to phosphate levels, suggesting that PT4 genes affect early root branching. Phosphate starvation-induced genes and a key auxin receptor, MtTIR1, showed an impaired expression in mtpt4 plants. We suggest PT4 genes as novel components of the P-sensing machinery at the root tip level, independently of AM fungi. This article is protected by copyright. All rights reserved.

Via Christophe Jacquet, Jean-Michel Ané
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Jean-Michel Ané's curator insight, March 18, 2016 8:26 AM

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Root Endophyte Colletotrichum tofieldiae Confers Plant Fitness Benefits that Are Phosphate Status Dependent: Cell

Root Endophyte Colletotrichum tofieldiae Confers Plant Fitness Benefits that Are Phosphate Status Dependent: Cell | MycorWeb Plant-Microbe Interactions | Scoop.it
A staggering diversity of endophytic fungi associate with healthy plants in nature, but it is usually unclear whether these represent stochastic encounters or provide host fitness benefits. Although most characterized species of the fungal genus Colletotrichum are destructive pathogens, we show here that C. tofieldiae (Ct) is an endemic endophyte in natural Arabidopsis thaliana populations in central Spain. Colonization by Ct initiates in roots but can also spread systemically into shoots. Ct transfers the macronutrient phosphorus to shoots, promotes plant growth, and increases fertility only under phosphorus-deficient conditions, a nutrient status that might have facilitated the transition from pathogenic to beneficial lifestyles. The host’s phosphate starvation response (PSR) system controls Ct root colonization and is needed for plant growth promotion (PGP). PGP also requires PEN2-dependent indole glucosinolate metabolism, a component of innate immune responses, indicating a functional link between innate immunity and the PSR system during beneficial interactions with Ct.
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Subcellular Compartmentalization and Trafficking of the Biosynthetic Machinery for Fungal Melanin

Subcellular Compartmentalization and Trafficking of the Biosynthetic Machinery for Fungal Melanin | MycorWeb Plant-Microbe Interactions | Scoop.it
Protection by melanin depends on its subcellular location. Although most filamentous fungi synthesize melanin via a polyketide synthase pathway, where and how melanin biosynthesis occurs and how it is deposited as extracellular granules remain elusive. Using a forward genetic screen in the pathogen Aspergillus fumigatus, we find that mutations in an endosomal sorting nexin abolish melanin cell-wall deposition. We find that all enzymes involved in the early steps of melanin biosynthesis are recruited to endosomes through a non-conventional secretory pathway. In contrast, late melanin enzymes accumulate in the cell wall. Such subcellular compartmentalization of the melanin biosynthetic machinery occurs in both A. fumigatus and A. nidulans. Thus, fungal melanin biosynthesis appears to be initiated in endosomes with exocytosis leading to melanin extracellular deposition, much like the synthesis and trafficking of mammalian melanin in endosomally derived melanosomes.
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De novo transcriptomic assembly and profiling of Rigidoporus during saprotrophic growth on rubber wood

De novo transcriptomic assembly and profiling of Rigidoporus during saprotrophic growth on rubber wood | MycorWeb Plant-Microbe Interactions | Scoop.it

Background. The basidiomycete Rigidoporus microporus is a fungus that causes the white rot disease of the tropical rubber tree, Hevea brasiliensis, the major source of commercial natural rubber. Besides its lifestyle as a pathogen, the fungus is known to switch to saprotrophic growth on wood with the ability to degrade both lignin and cellulose. There is almost no genomic or transcriptomic information on the saprotrophic abilities of this fungus. In this study, we present the fungal transcriptomic profiles during saprotrophic growth on rubber wood.


Results. A total of 266.6 million RNA-Seq reads were generated from six libraries of the fungus growing either on rubber wood or without wood. De novo assembly produced 34, 518 unigenes with an average length of 2179 bp. Annotation of unigenes using public databases; GenBank, Swiss-Prot, Kyoto Encyclopedia of Genes and Genomes (KEGG), Cluster of Orthologous Groups (COG) and Gene Ontology (GO) produced 25, 880 annotated unigenes. Transcriptomic profiling analysis revealed that the fungus expressed over 300 genes encoding lignocellulolytic enzymes. Among these, 175 genes were up-regulated in rubber wood. These include three members of the glycoside hydrolase family 43, as well as various glycosyl transferases, carbohydrate esterases and polysaccharide lyases. A large number of oxidoreductases which includes nine manganese peroxidases were also significantly up-regulated in rubber wood. Several genes involved in fatty acid metabolism and degradation as well as natural rubber degradation were expressed in the transcriptome. Four genes (acyl-CoA synthetase, enoyl-CoA hydratase, 3-hydroxyacyl-CoA dehydrogenase and acyl-CoA acetyltransferase) potentially involved in rubber latex degradation pathway were also induced. A number of ATP binding cassette (ABC) transporters and hydrophobin genes were significantly expressed in the transcriptome during saprotrophic growth. Some genes related to energy metabolism were also induced.


Conclusions. The analysed data gives an insight into the activation of lignocellulose breakdown machinery of R. microporus. This study also revealed genes with relevance in antibiotic metabolism (e.g. cephalosporin esterase) as well as those with potential applications in fatty acid degradation. This is the first study on the transcriptomic analysis of R. microporus on rubber wood and should serve as a pioneering resource for future studies of the fungus at the genomic or transcriptomic level.

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Peltaster fructicola genome reveals evolution from an invasive phytopathogen to an ectophytic parasite

Peltaster fructicola genome reveals evolution from an invasive phytopathogen to an ectophytic parasite | MycorWeb Plant-Microbe Interactions | Scoop.it
Sooty blotch and flyspeck (SBFS) fungi are unconventional plant pathogens that cause economic losses by blemishing the surface appearance of infected fruit. Here, we introduce the 18.14-Mb genome of Peltaster fructicola, one of the most prevalent SBFS species on apple. This undersized assembly contains only 8,334 predicted protein-coding genes and a very small repertoire of repetitive elements. Phylogenomics and comparative genomics revealed that P. fructicola had undergone a reductive evolution, during which the numbers of orphan genes and genes involved in plant cell wall degradation, secondary metabolism, and secreted peptidases and effectors were drastically reduced. In contrast, the genes controlling 1,8-dihydroxynaphthalene (DHN)-melanin biosynthesis and appressorium-mediated penetration were retained substantially. Additionally, microscopic examination of the surfaces of infected apple indicated for the first time that P. fructicola can not only dissolve epicuticular waxes but also partially penetrate the cuticle proper. Our findings indicate that genome contraction, characterized mainly by the massive loss of pathogenicity-related genes, has played an important role in the evolution of P. fructicola (and by implication other SBFS species) from a plant-penetrating ancestor to a non-invasive ectophyte, displaying a novel form of trophic interaction between plants and fungi.
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Characterization of the reproductive mode and life cycle of the whitish truffle Tuber borchii

Characterization of the reproductive mode and life cycle of the whitish truffle Tuber borchii | MycorWeb Plant-Microbe Interactions | Scoop.it
Truffles are the fruiting structures of ascomycetes in the genus Tuber. Because of their economic importance, truffles have been cultivated for many years using artificially inoculated host plants. Nevertheless, the life cycle and reproductive mode of Tuber spp. are still poorly understood. In filamentous ascomycetes, sexual reproduction is genetically controlled by the mating-type (MAT) locus. Among Tuber spp., the MAT locus has been recently characterized in the black truffles Tuber melanosporum and Tuber indicum. Here, by using sequence information derived from these species and from a Tuber borchii expressed sequence tag (EST) showing similarity to the mat1 gene of Alternaria brassicicola, we embarked on a chromosome-walking procedure to sequence the complete MAT region of T. borchii. This fungus produces highly commercialized whitish truffles and represents a model species for addressing basic questions concerning the life cycle of Tuber spp. We show that T. borchii is heterothallic, as its MAT locus is organized into two idiomorphs, each harbored by different mycelial strains. The alignment of the MAT locus from black truffles and T. borchii reveals that extensive sequence rearrangements and inversions occurred between these species. Moreover, by coupling mating-type analyses to karyological observation, we show that mycelia isolated from ascocarps and mycorrhizae are formed by homokaryotic hyphae.
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Nuclear DNA sequences from the Middle Pleistocene Sima de los Huesos hominins : Nature

Nuclear DNA sequences from the Middle Pleistocene Sima de los Huesos hominins : Nature | MycorWeb Plant-Microbe Interactions | Scoop.it
A unique assemblage of 28 hominin individuals, found in Sima de los Huesos in the Sierra de Atapuerca in Spain, has recently been dated to approximately 430,000 years ago1. An interesting question is how these Middle Pleistocene hominins were related to those who lived in the Late Pleistocene epoch, in particular to Neanderthals in western Eurasia and to Denisovans, a sister group of Neanderthals so far known only from southern Siberia. While the Sima de los Huesos hominins share some derived morphological features with Neanderthals, the mitochondrial genome retrieved from one individual from Sima de los Huesos is more closely related to the mitochondrial DNA of Denisovans than to that of Neanderthals2. However, since the mitochondrial DNA does not reveal the full picture of relationships among populations, we have investigated DNA preservation in several individuals found at Sima de los Huesos. Here we recover nuclear DNA sequences from two specimens, which show that the Sima de los Huesos hominins were related to Neanderthals rather than to Denisovans, indicating that the population divergence between Neanderthals and Denisovans predates 430,000 years ago. A mitochondrial DNA recovered from one of the specimens shares the previously described relationship to Denisovan mitochondrial DNAs, suggesting, among other possibilities, that the mitochondrial DNA gene pool of Neanderthals turned over later in their history.
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Does a Common Pathway Transduce Symbiotic Signals in Plant–Microbe Interactions?

Does a Common Pathway Transduce Symbiotic Signals in Plant–Microbe Interactions? | MycorWeb Plant-Microbe Interactions | Scoop.it
Recent years have witnessed major advances in our knowledge of plant mutualistic symbioses such as the rhizobium-legume symbiosis (RLS) and arbuscular mycorrhizas (AM). Some of these findings caused the revision of longstanding hypotheses, but one of the most solid theories is that a conserved set of plant proteins rules the transduction of symbiotic signals from beneficial glomeromycetes and rhizobia in a so-called common symbiotic pathway (CSP). Nevertheless, the picture still misses several elements, and a few crucial points remain unclear. How does one common pathway discriminate between – at least – two symbionts? Can we exclude that microbes other than AM fungi and rhizobia also use this pathway to communicate with their host plants? We here discuss the possibility that our current view is biased by a long-lasting focus on legumes, whose ability to develop both AM and RLS is an exception among plants and a recent innovation in their evolution; investigations in non-legumes are starting to place legume symbiotic signaling in a broader perspective. Furthermore, recent studies suggest that CSP proteins act in a wider scenario of symbiotic and non-symbiotic signaling. Overall, evidence is accumulating in favor of distinct activities for CSP proteins in AM and RLS, depending on the molecular and cellular context where they act.
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Rescooped by Francis Martin from Plants & Evolution
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The Genomes of Charophyte Green Algae

The charophyte green algae (sometimes called basal streptophytes) belong to the lineage that gave rise to land plants (embryophytes), but are distinguished by lacking a number of features and characteristics of land plants, most notably the land plant life cycle. Individually, many charophyte algae have been used as systems to study plant biology, but the realization that these organisms belong together as an evolutionary lineage dates only to ultrastructural studies in the 1970s, and a more detailed understanding of their relationships to each other and to land plants is still emerging. Currently recognized members of the group include Mesostigma, Chlorokybus, Klebsormidiophyceae, Charophyceae sensu stricto, Coleochaetophyceae and Zygnematophyceae (Conjugatophyceae). Contrary to earlier molecular systematic studies, Zygnematophyceae appear as the sister to land plants in current multigene phylogenetic analyses. Early studies reported chromosome numbers and morphologies, and identified polyploid series in the Zygnematophyceae and Charophyceae s. str., with less detailed chromosome counts in the other groups. Molecular studies using PCR and related methods to study individual genes and processes have been accelerated by high-throughput sequencing, particularly of transcriptomes. Both chloroplast and mitochondrial organellar genomes are available for representatives of each major subgroup, but the only near-complete nuclear genome currently available is that of Klebsormidium. There are several genome sequencing projects underway, and expansion of genomic data available should occur soon.

Via Pierre-Marc Delaux
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