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Rescooped by Francis Martin from Plant & Evolution
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Evidence for land plant cell wall biosynthetic mechanisms in charophyte green algae

Evidence for land plant cell wall biosynthetic mechanisms in charophyte green algae | MycorWeb Plant-Microbe Interactions | Scoop.it

 

Abstract

Background and Aims The charophyte green algae (CGA) are thought to be the closest living relatives to the land plants, and ancestral CGA were unique in giving rise to the land plant lineage. The cell wall has been suggested to be a defining structure that enabled the green algal ancestor to colonize land. These cell walls provide support and protection, are a source of signalling molecules, and provide developmental cues for cell differentiation and elongation. The cell wall of land plants is a highly complex fibre composite, characterized by cellulose cross-linked by non-cellulosic polysaccharides, such as xyloglucan, embedded in a matrix of pectic polysaccharides. How the land plant cell wall evolved is currently unknown: early-divergent chlorophyte and prasinophyte algae genomes contain a low number of glycosyl transferases (GTs), while land plants contain hundreds. The number of GTs in CGA is currently unknown, as no genomes are available, so this study sought to give insight into the evolution of the biosynthetic machinery of CGA through an analysis of available transcriptomes.

Methods Available CGA transcriptomes were mined for cell wall biosynthesis GTs and compared with GTs characterized in land plants. In addition, gene cloning was employed in two cases to answer important evolutionary questions.

Key Results Genetic evidence was obtained indicating that many of the most important core cell wall polysaccharides have their evolutionary origins in the CGA, including cellulose, mannan, xyloglucan, xylan and pectin, as well as arabino-galactan protein. Moreover, two putative cellulose synthase-like D family genes (CSLDs) from the CGA speciesColeochaete orbicularis and a fragment of a putative CSLA/K-like sequence from a CGA Spirogyra species were cloned, providing the first evidence that all the cellulose synthase/-like genes present in early-divergent land plants were already present in CGA.

Conclusions The results provide new insights into the evolution of cell walls and support the notion that the CGA were pre-adapted to life on land by virtue of the their cell wall biosynthetic capacity. These findings are highly significant for understanding plant cell wall evolution as they imply that some features of land plant cell walls evolved prior to the transition to land, rather than having evolved as a result of selection pressures inherent in this transition.


Via Pierre-Marc Delaux
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Deep-biosphere consortium of fungi and prokaryotes in Eocene subseafloor basalts

Deep-biosphere consortium of fungi and prokaryotes in Eocene subseafloor basalts | MycorWeb Plant-Microbe Interactions | Scoop.it

The deep biosphere of the subseafloor crust is believed to contain a significant part of Earth's biomass, but because of the difficulties of directly observing the living organisms, its composition and ecology are poorly known. We report here a consortium of fossilized prokaryotic and eukaryotic micro-organisms, occupying cavities in deep-drilled vesicular basalt from the Emperor Seamounts, Pacific Ocean, 67.5 m below seafloor (mbsf). Fungal hyphae provide the framework on which prokaryote-like organisms are suspended like cobwebs and iron-oxidizing bacteria form microstromatolites (Frutexites). The spatial inter-relationships show that the organisms were living at the same time in an integrated fashion, suggesting symbiotic interdependence. The community is contemporaneous with secondary mineralizations of calcite partly filling the cavities. The fungal hyphae frequently extend into the calcite, indicating that they were able to bore into the substrate through mineral dissolution. A symbiotic relationship with chemoautotrophs, as inferred for the observed consortium, may be a pre-requisite for the eukaryotic colonization of crustal rocks. Fossils thus open a window to the extant as well as the ancient deep biosphere.

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Steve Marek's curator insight, September 17, 2014 2:51 PM

Rock-drilling fungi and bacteria!

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Frontiers | Control of arbuscular mycorrhiza development by nutrient signals | Plant Physiology

Inorganic phosphate (Pi), the main form of phosphorus used by plants, is one of the most important limiting factors for plant growth. In the soil soluble Pi that is readily available for uptake, occurs at very low concentrations (Schachtman et al., 1998). One adaptation of plants to low Pi availability is the symbiosis with arbuscular mycorrhiza fungi (AMF) of the phylum Glomeromycota. The fungi efficiently take up phosphate and other mineral nutrients and deliver them to the host, in exchange for carbohydrates. Thereby, arbuscular-mycorrhiza compatible plants have two Pi uptake pathways, which are defined by different sets of phosphate transporters: a direct uptake pathway through the epidermis and root hairs, and a symbiotic uptake pathway for the Pi provided by the fungus (Smith and Smith, 2011).

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Rescooped by Francis Martin from Plant & Evolution
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Storify: #NPW10 Origin and evolution of plants and their interactions with fungi. 9–10 September 2014


Via Kamoun Lab @ TSL, Pierre-Marc Delaux
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Rescooped by Francis Martin from Plants and Microbes
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10th New Phytologist Workshop: Origin and evolution of plants and their interactions with fungi, 9–10 September 2014, Natural History Museum, London, UK

10th New Phytologist Workshop: Origin and evolution of plants and their interactions with fungi, 9–10 September 2014, Natural History Museum, London, UK | MycorWeb Plant-Microbe Interactions | Scoop.it

Our overall goal is to understand how plants and their eukaryotic symbionts (fungi and fungi-like microorganisms, especially oomycetes) co-evolved during the early development of terrestrial ecosystems. Several diverse and rapidly developing disciplines are relevant to addressing this goal. Our workshop is designed to bringing together experts from across these disciplines to learn about recent developments, understand the range of approaches and to explore potential cross disciplinary collaborations.

 

1. We will bring together a multidisciplinary group of specialists in the biology and phylogenetics of living bryophytes and of fungi, experts on the evolution of plant-­‐fungal interactions (biochemical/physiological/ecological) and specialists on the early fossil record. Our focus will be to determine how expertise in these diverse disciplines could be harnessed to investigate the early evolution of key events, metabolic pathways, and symbiotic associations.

 

2. We will identify themes which cut across the different disciplines and how best to harness collaboration. For example, recent genomic and molecular clock analyses indicate that the origin of lignin decomposition coincided with the end of the Carboniferous Period. A carefully constructed investigation of Palaeozoic Era fossil plants (e.g. evidence of white rots) and analyses of sediment geochemistry documenting could test these hypotheses. A second area of interest is arbuscular mycorrhizal symbioses, where much remains to be learned about the early evolution of the trait. This would benefit from focused discussion by experts on living bryophyte/fungal systems, developmental biologists and palaeontologists. A third area of interest is the early evolution and development of soil ecosystems, in which the identification and characterisation of modern analogues could greatly assist interpretation of sediments in the early fossil record.

 

3. The proposed workshop is a first step in community collaboration. We will look for ways to develop and strengthen collaboration at an international level. We envisage building a scheme of communication and knowledge sharing through laboratory exchange visits, and to take the field forward we intend to explore the possibility of developing multidisciplinary research networks/consortia.

 
Via Kamoun Lab @ TSL
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Rescooped by Francis Martin from The Plant Microbiome
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eLIFE: Active invasion of bacteria into living fungal cells

eLIFE: Active invasion of bacteria into living fungal cells | MycorWeb Plant-Microbe Interactions | Scoop.it

The rice seedling blight fungus Rhizopus microsporus and its endosymbiont Burkholderia rhizoxinica form an unusual, highly specific alliance to produce the highly potent antimitotic phytotoxin rhizoxin. Yet, it has remained a riddle how bacteria invade into the fungal cells. Genome mining for potential symbiosis factors and functional analyses revealed that a type 2 secretion system (T2SS) of the bacterial endosymbiont is required for the formation of the endosymbiosis. Comparative proteome analyses show that the T2SS releases chitinolytic enzymes (chitinase, chitosanase) and chitin-binding proteins. The genes responsible for chitinolytic proteins and T2SS components are highly expressed during infection. Through targeted gene knock-outs, sporulation assays and microscopic investigations we found that chitinase is essential for bacteria to enter hyphae. Unprecedented snapshots of the traceless bacterial intrusion were obtained using cryo-electron microscopy. Beyond unveiling the pivotal role of chitinolytic enzymes in the active invasion of a fungus by bacteria, these findings grant unprecedented insight into the fungal cell wall penetration and symbiosis formation.


Via Stéphane Hacquard
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The coffee genome provides insight into the convergent evolution of caffeine biosynthesis

The coffee genome provides insight into the convergent evolution of caffeine biosynthesis | MycorWeb Plant-Microbe Interactions | Scoop.it

Coffee is a valuable beverage crop due to its characteristic flavor, aroma, and the stimulating effects of caffeine. We generated a high-quality draft genome of the species Coffea canephora, which displays a conserved chromosomal gene order among asterid angiosperms. Although it shows no sign of the whole-genome triplication identified in Solanaceae species such as tomato, the genome includes several species-specific gene family expansions, among them N-methyltransferases (NMTs) involved in caffeine production, defense-related genes, and alkaloid and flavonoid enzymes involved in secondary compound synthesis. Comparative analyses of caffeine NMTs demonstrate that these genes expanded through sequential tandem duplications independently of genes from cacao and tea, suggesting that caffeine in eudicots is of polyphyletic origin.

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Rescooped by Francis Martin from Plant & Evolution
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The origin and early evolution of roots

The origin and early evolution of roots | MycorWeb Plant-Microbe Interactions | Scoop.it

Geological sites of exceptional fossil preservation are becoming a focus of research on root evolution because they retain edaphic and ecological context, and in some the remains of plant soft tissues are preserved. New information is emerging on the origins of rooting systems, their interactions with fungi, and on their nature and diversity in the earliest forest ecosystems. Remarkably well-preserved fossils prove that mycorrhizal symbionts were diverse in simple rhizoid-based systems. Roots evolved in a piecemeal fashion and independently in several major clades through the Devonian Period (416-360 Myr), rapidly extending functionality and complexity. Evidence from extinct arborescent clades indicates that polar auxin transport was recruited independently in several to regulate wood and root development. The broader impact of root evolution on the geochemical carbon cycle is a developing area and one in which the interests of the plant physiologist intersect with those of the geochemist.


Via Pierre-Marc Delaux
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The genomic substrate for adaptive radiation in African cichlid fish : Nature

The genomic substrate for adaptive radiation in African cichlid fish : Nature | MycorWeb Plant-Microbe Interactions | Scoop.it

Cichlid fishes are famous for large, diverse and replicated adaptive radiations in the Great Lakes of East Africa. To understand the molecular mechanisms underlying cichlid phenotypic diversity, we sequenced the genomes and transcriptomes of five lineages of African cichlids: the Nile tilapia (Oreochromis niloticus), an ancestral lineage with low diversity; and four members of the East African lineage: Neolamprologus brichardi/pulcher (older radiation, Lake Tanganyika), Metriaclima zebra(recent radiation, Lake Malawi), Pundamilia nyererei (very recent radiation, Lake Victoria), andAstatotilapia burtoni (riverine species around Lake Tanganyika). We found an excess of gene duplications in the East African lineage compared to tilapia and other teleosts, an abundance of non-coding element divergence, accelerated coding sequence evolution, expression divergence associated with transposable element insertions, and regulation by novel microRNAs. In addition, we analysed sequence data from sixty individuals representing six closely related species from Lake Victoria, and show genome-wide diversifying selection on coding and regulatory variants, some of which were recruited from ancient polymorphisms. We conclude that a number of molecular mechanisms shaped East African cichlid genomes, and that amassing of standing variation during periods of relaxed purifying selection may have been important in facilitating subsequent evolutionary diversification.

  
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Ectomycorrhizal fungi have larger fruit bodies than saprotrophic fungi

Ectomycorrhizal fungi have larger fruit bodies than saprotrophic fungi | MycorWeb Plant-Microbe Interactions | Scoop.it

Currently we have only a limited understanding of the evolutionary and ecological significance of reproductive traits of fungi. We compared data on fruit body size, spore size and shape between saprotrophic and mutualistic (ectomycorrhizal) fungi in Northern and Central Europe. Lifestyle and reproductive traits showed strong phylogenetic signals. A phylogenetically informed analysis demonstrated that saprotrophs produce on average smaller fruit bodies than mutualistic species. The two guilds, however, do not differ in spore size. Overall this suggests that fruit bodies of ectomycorrhizal fungi produce on average more spores than saprotrophic fungi. We argue that this difference is related to resource availability: ectomycorrhizal fungi receive carbon from their hosts and, therefore, evolution favours large fruit bodies, whereas the fruit body size of saprotrophic fungi might have responded to resource availability and the distribution and size of resource patches.

  
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Multiscale digital Arabidopsis predicts individual organ and whole-organism growth

Multiscale digital Arabidopsis predicts individual organ and whole-organism growth | MycorWeb Plant-Microbe Interactions | Scoop.it

Understanding how dynamic molecular networks affect whole-organism physiology, analogous to mapping genotype to phenotype, remains a key challenge in biology. Quantitative models that represent processes at multiple scales and link understanding from several research domains can help to tackle this problem. Such integrated models are more common in crop science and ecophysiology than in the research communities that elucidate molecular networks. Several laboratories have modeled particular aspects of growth inArabidopsis thaliana, but it was unclear whether these existing models could productively be combined. We test this approach by constructing a multiscale model of Arabidopsis rosette growth. Four existing models were integrated with minimal parameter modification (leaf water content and one flowering parameter used measured data). The resulting framework model links genetic regulation and biochemical dynamics to events at the organ and whole-plant levels, helping to understand the combined effects of endogenous and environmental regulators on Arabidopsis growth. The framework model was validated and tested with metabolic, physiological, and biomass data from two laboratories, for five photoperiods, three accessions, and a transgenic line, highlighting the plasticity of plant growth strategies. The model was extended to include stochastic development. Model simulations gave insight into the developmental control of leaf production and provided a quantitative explanation for the pleiotropic developmental phenotype caused by overexpression of miR156, which was an open question. Modular, multiscale models, assembling knowledge from systems biology to ecophysiology, will help to understand and to engineer plant behavior from the genome to the field.

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Rescooped by Francis Martin from Plant-Microbe Symbioses
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Genomic and transcriptomic analysis of Laccaria bicolor CAZome reveals insights into polysaccharides remodelling during symbiosis establishment

Genomic and transcriptomic analysis of Laccaria bicolor CAZome reveals insights into polysaccharides remodelling during symbiosis establishment | MycorWeb Plant-Microbe Interactions | Scoop.it

Ectomycorrhizal fungi, living in soil forests, are required microorganisms to sustain tree growth and productivity. The establishment of mutualistic interaction with roots to form ectomycorrhiza (ECM) is not well known at the molecular level. In particular, how fungal and plant cell walls are rearranged to establish a fully functional ectomycorrhiza is poorly understood. Nevertheless, it is likely that Carbohydrate Active enZymes (CAZyme) produced by the fungus participate in this process.

Genome-wide transcriptome profiling during ECM development was used to examine how the CAZome of L. bicolor is regulated during symbiosis establishment.

CAZymes active on fungal cell wall were upregulated during ECM development in particular after 4 weeks of contact when the hyphae are surrounding the root cells and start to colonize the apoplast. We demonstrated that one expansin-like protein, whose expression is specific to symbiotic tissues, localizes within fungal cell wall.

Whereas L. bicolor genome contained a constricted repertoire of CAZymes active on cellulose and hemicellulose, these CAZymes were expressed during the first steps of root cells colonization. L. bicolor retained the ability to use homogalacturonan, a pectin-derived substrate, as carbon source. CAZymes likely involved in pectin hydrolysis were mainly expressed at the stage of a fully mature ECM.

All together, our data suggest an active remodelling of fungal cell wall with a possible involvement of expansin during ECM development. By contrast, a soft remodelling of the plant cell wall likely occurs through the loosening of the cellulose microfbrils by AA9 or GH12 CAZymes and middle lamella smooth remodelling through pectin (homogalacturonan) hydrolysis likely by GH28, GH12 CAZymes.


Via Jean-Michel Ané
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Frontiers | Unraveling plant hormone signaling through the use of small molecules

Plants have acquired the capacity to grow continuously and adjust their morphology in response to endogenous and external signals, leading to a high architectural plasticity. The dynamic and differential distribution of phytohormones is an essential factor in these developmental changes. Phytohormone perception is a fast but complex process modulating specific developmental reprogramming. In recent years, chemical genomics or the use of small molecules to modulate target protein function has emerged as a powerful strategy to study complex biological processes in plants such as hormone signaling. Small molecules can be applied in a conditional, dose-dependent and reversible manner, with the advantage of circumventing the limitations of lethality and functional redundancy inherent to traditional mutant screens. High-throughput screening of diverse chemical libraries has led to the identification of bioactive molecules able to induce plant hormone-related phenotypes. Characterization of the cognate targets and pathways of those molecules has allowed the identification of novel regulatory components, providing new insights into the molecular mechanisms of plant hormone signaling. An extensive structure-activity relationship (SAR) analysis of the natural phytohormones, their designed synthetic analogues and newly identified bioactive molecules has led to the determination of the structural requirements essential for their bioactivity. In this review, we will summarize the so far identified small molecules and their structural variants targeting specific phytohormone signaling pathways. We will highlight how the SAR analyses have enabled better interrogation of the molecular mechanisms of phytohormone responses. Finally, we will discuss how labeled/tagged hormone analogues can be exploited, as compelling tools to better understand hormone signaling and transport mechanisms.
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The Ins and Outs of Rust Haustoria

The Ins and Outs of Rust Haustoria | MycorWeb Plant-Microbe Interactions | Scoop.it

Rust diseases caused by fungi of the order Pucciniales afflict a wide range of plants, including cereals, legumes, ornamentals, and fruit trees, and pose a serious threat to cropping systems and global food security. The obligate parasitic lifestyle of these fungi and their complex life cycles, often involving alternate hosts for the sexual and asexual stages, also make this group of pathogens of great biological interest. One of the most remarkable adaptations of rust fungi is the specialized infection structure that underpins the sustained biotrophic association with hosts; the haustorium (Figure 1A and C). This organ forms after penetration of the wall of a live host cell, expanding on the inner side of the cell wall while invaginating the surrounding host plasma membrane (Figure 1C). Through haustoria, the pathogen derives nutrients from the host and secretes virulence proteins called effectors, which are believed to be the key players that manipulate the physiological and immune responses of host cells [1]–[4]. Analogous terminal feeding structures have independently evolved in other organisms such as the haustorium in powdery mildews (ascomycetes) and downy mildews (oomycetes, not true fungi), and the arbuscules in arbuscular mycorrhizae, suggesting that such architecture represents a successful adaptation of these organisms to interact with their respective host plants [5], [6].

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Convergent Targeting of a Common Host Protein-Network by Pathogen Effectors from Three Kingdoms of Life

Convergent Targeting of a Common Host Protein-Network by Pathogen Effectors from Three Kingdoms of Life | MycorWeb Plant-Microbe Interactions | Scoop.it

While conceptual principles governing plant immunity are becoming clear, its systems-level organization and the evolutionary dynamic of the host-pathogen interface are still obscure. We generated a systematic protein-protein interaction network of virulence effectors from the ascomycete pathogen Golovinomyces orontii andArabidopsis thaliana host proteins. We combined this data set with corresponding data for the eubacterial pathogen Pseudomonas syringae and the oomycete pathogen Hyaloperonospora arabidopsidis. The resulting network identifies host proteins onto which intraspecies and interspecies pathogen effectors converge. Phenotyping of 124 Arabidopsis effector-interactor mutants revealed a correlation between intraspecies and interspecies convergence and several altered immune response phenotypes. Several effectors and the most heavily targeted host protein colocalized in subnuclear foci. Products of adaptively selected Arabidopsis genes are enriched for interactions with effector targets. Our data suggest the existence of a molecular host-pathogen interface that is conserved across Arabidopsis accessions, while evolutionary adaptation occurs in the immediate network neighborhood of effector targets.

  
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Rescooped by Francis Martin from Plant Pathogenomics
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MPMI: The genome of the saprophytic fungus Verticillium tricorpus reveals a complex effector repertoire resembling that of its pathogenic relatives (2014)

MPMI: The genome of the saprophytic fungus Verticillium tricorpus reveals a complex effector repertoire resembling that of its pathogenic relatives (2014) | MycorWeb Plant-Microbe Interactions | Scoop.it

Vascular wilts caused by Verticillium spp. are destructive plant diseases, affecting hundreds of hosts. Only few Verticillium spp. are causal agents of vascular wilt diseases, of which V. dahliae is the most notorious pathogen, and several V. dahliae genomes are available. In contrast, V. tricorpus is mainly known as saprophyte and causal agent of opportunistic infections. Based on a hybrid approach that combines second and third generation sequencing, a near-gapless V. tricorpus genome assembly was obtained. With comparative genomics, we aimed to identify genomic features in V. dahliae that confer the ability to cause vascular wilt disease. Unexpectedly, both species encode similar effector repertoires and share a genomic structure with genes encoding secreted proteins clustered in genomic islands. Intriguingly, V. tricorpus contains significantly less repetitive elements and an extended spectrum of secreted carbohydrate-active enzymes when compared with V. dahliae. In conclusion, we highlight the technical advances of a hybrid sequencing and assembly approach and reveal that the saprophyte V. tricorpus shares many hallmark features with V. dahliae.


Via Kamoun Lab @ TSL
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Biology Letters: The dawn of symbiosis between plants and fungi (2011)

Biology Letters: The dawn of symbiosis between plants and fungi (2011) | MycorWeb Plant-Microbe Interactions | Scoop.it

The colonization of land by plants relied on fundamental biological innovations, among which was symbiosis with fungi to enhance nutrient uptake. Here we present evidence that several species representing the earliest groups of land plants are symbiotic with fungi of the Mucoromycotina. This finding brings up the possibility that terrestrialization was facilitated by these fungi rather than, as conventionally proposed, by members of the Glomeromycota. Since the 1970s it has been assumed, largely from the observation that vascular plant fossils of the early Devonian (400 Ma) show arbuscule-like structures, that fungi of the Glomeromycota were the earliest to form mycorrhizas, and evolutionary trees have, until now, placed Glomeromycota as the oldest known lineage of endomycorrhizal fungi. Our observation that Endogone-like fungi are widely associated with the earliest branching land plants, and give way to glomeromycotan fungi in later lineages, raises the new hypothesis that members of the Mucoromycotina rather than the Glomeromycota enabled the establishment and growth of early land colonists.


Via Kamoun Lab @ TSL
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Metatranscriptomic analysis of ectomycorrhizal roots reveal genes associated with Piloderma-Pinus symbiosis: Improved methodologies for assessing gene expression in situ

Metatranscriptomic analysis of ectomycorrhizal roots reveal genes associated with Piloderma-Pinus symbiosis: Improved methodologies for assessing gene expression in situ | MycorWeb Plant-Microbe Interactions | Scoop.it

Ectomycorrhizal (EM) fungi form symbiotic associations with plant roots that regulate nutrient exchange between forest plants and soil. Environmental metagenomics approaches that employ next-generation sequencing show great promise for studying EM symbioses, however, metatranscriptomic studies have been constrained by the inherent difficulties associated with isolation and sequencing of RNA from mycorrhizae. Here we apply an optimized method for combined DNA/RNA extraction using field-collected EM fungal-pine root clusters, together with protocols for taxonomic identification of expressed ribosomal RNA, and inference of EM function based on plant and fungal metatranscriptomics. We used transcribed portions of ribosomal RNA genes to identify several transcriptionally dominant fungal taxa associated with loblolly pine including Amphinema, Russula, and Piloderma spp. One taxon, Piloderma croceum, has a publically available genome that allowed us to identify patterns of gene content and transcript abundance. Over 1500 abundantly expressed Piloderma genes were detected from mycorrhizal roots, including genes for protein metabolism, cell signaling, electron transport, terpene synthesis, and other extracellular activities. In contrast, Piloderma gene encoding an ammonia transporter showed highest transcript abundance in soil samples. Our methodology highlights the potential of metatranscriptomics to identify genes associated with symbiosis and ecosystem function using field-collected samples.

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A wake-up call with coffee

A wake-up call with coffee | MycorWeb Plant-Microbe Interactions | Scoop.it

The captain of the starship Voyager from one of the latter-dayStar Trek television series expressed the sentiments of many by stating: “Coffee, the finest organic suspension ever devised.” On page 1181, Denoeud et al. present a draft genome of the diploidCoffea canephora (1), one of the two founder species of the tetraploid crop Coffea arabica. Coffee, the plant bearing the irresistible bean that delivers the most widely consumed psychoactive drug in the world—caffeine—joins a long list of crop species that have been sequenced using ever-improving genomic hardware and assembly software (2). High-quality genome assemblies facilitate the resequencing of many cultivated varieties, landraces (local ecotypes), and sometimes wild, crop-related species. The challenge now is to translate these decoded genomes into new and improved tools for plant breeding; there is a need for a better balance of research priorities, with greater emphasis on crop phenotypes.

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Temperature sensitivity of soil respiration rates enhanced by microbial community response : Nature

Temperature sensitivity of soil respiration rates enhanced by microbial community response : Nature | MycorWeb Plant-Microbe Interactions | Scoop.it
Soils store about four times as much carbon as plant biomass, and soil microbial respiration releases about 60 petagrams of carbon per year to the atmosphere as carbon dioxide. Short-term experiments have shown that soil microbial respiration increases exponentially with temperature. This information has been incorporated into soil carbon and Earth-system models, which suggest that warming-induced increases in carbon dioxide release from soils represent an important positive feedback loop that could influence twenty-first-century climate change. The magnitude of this feedback remains uncertain, however, not least because the response of soil microbial communities to changing temperatures has the potential to either decrease or increase warming-induced carbon losses substantially. Here we collect soils from different ecosystems along a climate gradient from the Arctic to the Amazon and investigate how microbial community-level responses control the temperature sensitivity of soil respiration. We find that the microbial community-level response more often enhances than reduces the mid- to long-term (90 days) temperature sensitivity of respiration. Furthermore, the strongest enhancing responses were observed in soils with high carbon-to-nitrogen ratios and in soils from cold climatic regions. After 90 days, microbial community responses increased the temperature sensitivity of respiration in high-latitude soils by a factor of 1.4 compared to the instantaneous temperature response. This suggests that the substantial carbon stores in Arctic and boreal soils could be more vulnerable to climate warming than currently predicted.
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Life outside the lab: The ones who got away

Life outside the lab: The ones who got away | MycorWeb Plant-Microbe Interactions | Scoop.it
Sometimes, the brightest stars in science decide to leave. Nature finds out where they go.
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Evolutionary biology: Radiating genomes : Nature : Nature Publishing Group

Evolutionary biology: Radiating genomes : Nature : Nature Publishing Group | MycorWeb Plant-Microbe Interactions | Scoop.it
Genome sequences and gene-expression data from representatives of five distinct lineages of African cichlid fish reveal signatures of the genomic changes that underlie the astounding cichlid diversity seen today.
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A biological market analysis of the plant-mycorrhizal symbiosis

A biological market analysis of the plant-mycorrhizal symbiosis | MycorWeb Plant-Microbe Interactions | Scoop.it

It has been argued that cooperative behavior in the plant-mycorrhizal mutualism resembles trade in a market economy and can be understood using economic tools. Here, we assess the validity of this “biological market” analogy by investigating whether a market mechanism—that is, competition between partners over the price at which they provide goods—could be the outcome of natural selection. Then, we consider the conditions under which this market mechanism is sufficient to maintain mutualistic trade. We find that: (i) as in a market, individuals are favored to divide resources among trading partners in direct relation to the relative amount of resources received, termed linear proportional discrimination; (ii) mutualistic trade is more likely to be favored when individuals are able to interact with more partners of both species, and when there is a greater relative difference between the species in their ability to directly acquire different resources; (iii) if trade is favored, then either one or both species is favored to give up acquiring one resource directly, and vice versa. We then formulate testable predictions as to how environmental changes and coevolved responses of plants and mycorrhizal fungi will influence plant fitness (crop yields) in agricultural ecosystems.

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Palaeotropical origins, boreotropical distribution and increased rates of diversification in a clade of edible ectomycorrhizal mushrooms (Amanita section Caesareae)

Palaeotropical origins, boreotropical distribution and increased rates of diversification in a clade of edible ectomycorrhizal mushrooms (Amanita section Caesareae) | MycorWeb Plant-Microbe Interactions | Scoop.it

Aim

The geographical distributions of most fungal species are still poorly known; consequently, their origins and historical distributions remain largely understudied. High levels of cryptic diversity, scarce fossil records and poorly sampled regions can explain some of these shortcomings. We extensively sampled an iconic group of edible ectomycorrhizal (EM) fungi, Amanita caesarea and its allies, in order to infer evolutionary patterns on a global scale.

Location

Worldwide.

Methods

DNA sequences from three nuclear genes were derived for 120 collections. Divergence times were estimated using fossil calibrations within the Agaricomycetes, followed by more inclusive (A. sect. Caesareae + outgroup) root-recalibrated estimations. Ultrametric trees from beast were used in ancestral-area reconstructions and to infer geodispersal models. They were further used in diversification-rate analyses using maximum-likelihood and Bayesian methods.

Results

Molecular dating and ancestral-area reconstruction indicated a Palaeotropical origin of A. sect. Caesareae between the Palaeocene and Eocene. Dispersal events to temperate regions in Mediterranean Europe, eastern Australia and North and Central America, occurred mostly during the late Miocene and Pliocene. A boreotropical model was supported as the most likely mode of geodispersal. Diversification rates were significantly higher in the New World than in the Old World.

Main conclusions

We present evidence that this group of edible EM mushrooms was ancestrally Palaeotropical from around the Eocene to the late Miocene, reaching temperate insular and continental areas during the late Miocene and Pliocene. The mode of dispersal is largely consistent with Wolfe's boreotropical hypothesis. We also found that the overall diversification rate has been rather constant, but has increased relatively recently in the New World, possibly as a result of the well-documented Plio-Pleistocene climatic fluctuations.


Via Jean-Michel Ané
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The toolbox of Trichoderma spp. in biocontrol of Botrytis cinerea disease

The toolbox of Trichoderma spp. in biocontrol of Botrytis cinerea disease | MycorWeb Plant-Microbe Interactions | Scoop.it

Botrytis cinerea is a necrotrophic fungal pathogen causing disease in many plant species leading to economically important crop losses. So far, fungicides are widely used to control this pathogen. However, in addition to their detrimental effects on the environment and potential risks for human health, increasing fungicide resistance has been observed in the B. cinerea population. Biological control, implying the application of microbial organisms to reduce disease, has gained importance as an alternative or complementary approach to fungicides. In this respect, the genus Trichoderma constitutes a promising pool of organisms with potential for B. cinerea control. In the first part we review the specific mechanisms involved in the direct interaction between the two fungi, including mycoparasitism, the production of antimicrobial compounds and enzymes (collectively called antagonism) and competition for nutrients and space. In addition, biocontrol has also been observed when Trichoderma was physically separated from the pathogen, thus implying an indirect systemic plant defence response. Therefore, in the second part we describe the consecutive steps leading to induced systemic resistance (ISR), starting with the initial Trichoderma-plant interaction followed by the activation of downstream signal transduction pathways and ultimately the defence response resulting in ISR (ISR-prime phase). Finally, we discuss the ISR-boost phase, representing the effect of the ISR-priming by Trichoderma spp. on plant responses after additional challenge with B. cinerea.


Via Christophe Jacquet
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