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A Distinct Role of Pectate Lyases in the Formation of Feeding Structures Induced by Cyst and Root-Knot Nematodes

A Distinct Role of Pectate Lyases in the Formation of Feeding Structures Induced by Cyst and Root-Knot Nematodes | MycorWeb Plant-Microbe Interactions | Scoop.it

Pectin in the primary plant cell wall is thought to be responsible for its porosity, charge density, and microfibril spacing and is the main component of the middle lamella. Plant-parasitic nematodes secrete cell wall–degrading enzymes that macerate the plant tissue, facilitating the penetration and migration within the roots. In sedentary endoparasitic nematodes, these enzymes are released only during the migration of infective juveniles through the root. Later, nematodes manipulate the expression of host plant genes, including various cell wall enzymes, in order to induce specific feeding sites. In this study, we investigated expression of two Arabidopsis pectate lyase-like genes (PLL), PLL18(At3g27400) and PLL19 (At4g24780), together with pectic epitopes with different degrees of methylesterification in both syncytia induced by the cyst nematode Heterodera schachtii and giant cells induced by the root-knot nematode Meloidogyne incognita. We confirmed upregulation ofPLL18 and PLL19 in both types of feeding sites with quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) and in situ RT-PCR. Furthermore, the functional analysis of mutants demonstrated the important role of both PLL genes in the development and maintenance of syncytia but not giant cells. Our results show that both enzymes play distinct roles in different infected root tissues as well as during parasitism of different nematodes.

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Novel findings on the role of signal exchange in arbuscular and ectomycorrhizal symbioses

Novel findings on the role of signal exchange in arbuscular and ectomycorrhizal symbioses | MycorWeb Plant-Microbe Interactions | Scoop.it

The availability of genome sequences from both arbuscular and ectomycorrhizal fungi and their hosts has, together with elegant biochemical and molecular biological analyses, provided new information on signal exchange between the partners in mycorrhizal associations. The progress in understanding cellular processes has been more rapid in arbuscular than ectomycorrhizal symbiosis due to its similarities of early processes with Rhizobium-legume symbiosis. In ectomycorrhiza, the role of auxin and ethylene produced by both fungus and host plant is becoming understood at the molecular level, although the actual ligands and receptors leading to ectomycorrhizal symbiosis have not yet been discovered. For both systems, the functions of small effector proteins secreted from the respective fungus and taken up into the plant cell may be pivotal in understanding the attenuation of host defense. We review the subject by comparing cross-talk between fungal and plant partners during formation and establishment of arbuscular and ectomycorrhizal symbioses.

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Amazed by the number of review papers released recently on signals, effectors and signaling pathways in mycorrhiza while the number of research papers remains very scarce.

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Molecular cartography of the human skin surface in 3D

Molecular cartography of the human skin surface in 3D | MycorWeb Plant-Microbe Interactions | Scoop.it

The human skin is an organ with a surface area of 1.5–2 m2 that provides our interface with the environment. The molecular composition of this organ is derived from host cells, microbiota, and external molecules. The chemical makeup of the skin surface is largely undefined. Here we advance the technologies needed to explore the topographical distribution of skin molecules, using 3D mapping of mass spectrometry data and microbial 16S rRNA amplicon sequences. Our 3D maps reveal that the molecular composition of skin has diverse distributions and that the composition is defined not only by skin cells and microbes but also by our daily routines, including the application of hygiene products. The technological development of these maps lays a foundation for studying the spatial relationships of human skin with hygiene, the microbiota, and environment, with potential for developing predictive models of skin phenotypes tailored to individual health

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GATA-Dependent Glutaminolysis Drives Appressorium Formation in Magnaporthe oryzae by Suppressing TOR Inhibition of cAMP/PKA Signaling

GATA-Dependent Glutaminolysis Drives Appressorium Formation in  Magnaporthe oryzae  by Suppressing TOR Inhibition of cAMP/PKA Signaling | MycorWeb Plant-Microbe Interactions | Scoop.it
Author Summary Many fungal pathogens destroy important crops by first gaining entrance to the host using specialized appressorial cells. Understanding the molecular mechanisms that control appressorium formation could provide new routes for managing severe plant diseases. Here, we describe a previously unknown regulatory pathway that suppresses appressorium formation by the rice pathogen Magnaporthe oryzae . We provide evidence that a mutant M . oryzae strain, unable to form appressoria,
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Phytophthora effector targets a novel component of small RNA pathway in plants to promote infection

Phytophthora effector targets a novel component of small RNA pathway in plants to promote infection | MycorWeb Plant-Microbe Interactions | Scoop.it
A broad range of parasites rely on the functions of effector proteins to subvert host immune response and facilitate disease development. The notorious Phytophthora pathogens evolved effectors with RNA silencing suppression activity to promote infection in plant hosts. Here we report that the Phytophthora Suppressor of RNA Silencing 1 (PSR1) can bind to an evolutionarily conserved nuclear protein containing the aspartate–glutamate–alanine–histidine-box RNA helicase domain in plants. This protein, designated PSR1-Interacting Protein 1 (PINP1), regulates the accumulation of both microRNAs and endogenous small interfering RNAs in Arabidopsis. A null mutation of PINP1 causes embryonic lethality, and silencing of PINP1 leads to developmental defects and hypersusceptibility to Phytophthora infection. These phenotypes are reminiscent of transgenic plants expressing PSR1, supporting PINP1 as a direct virulence target of PSR1. We further demonstrate that the localization of the Dicer-like 1 protein complex is impaired in the nucleus of PINP1-silenced or PSR1-expressing cells, indicating that PINP1 may facilitate small RNA processing by affecting the assembly of dicing complexes. A similar function of PINP1 homologous genes in development and immunity was also observed in Nicotiana benthamiana. These findings highlight PINP1 as a previously unidentified component of RNA silencing that regulates distinct classes of small RNAs in plants. Importantly, Phytophthora has evolved effectors to target PINP1 in order to promote infection.
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Molecular signals required for the establishment and maintenance of ectomycorrhizal symbioses - Garcia - 2015 - New Phytologist - Wiley Online Library

Molecular signals required for the establishment and maintenance of ectomycorrhizal symbioses - Garcia - 2015 - New Phytologist - Wiley Online Library | MycorWeb Plant-Microbe Interactions | Scoop.it

Ectomycorrhizal (ECM) symbioses are among the most widespread associations between roots of woody plants and soil fungi in forest ecosystems. These associations contribute significantly to the sustainability and sustainagility of these ecosystems through nutrient cycling and carbon sequestration. Unfortunately, the molecular mechanisms controlling the mutual recognition between both partners are still poorly understood. Elegant work has demonstrated that effector proteins from ECM and arbuscular mycorrhizal (AM) fungi regulate host defenses by manipulating plant hormonal pathways. In parallel, genetic and evolutionary studies in legumes showed that a ‘common symbiosis pathway’ is required for the establishment of the ancient AM symbiosis and has been recruited for the rhizobia–legume association. Given that genes of this pathway are present in many angiosperm trees that develop ectomycorrhizas, we propose their potential involvement in some but not all ECM associations. The maintenance of a successful long-term relationship seems strongly regulated by resource allocation between symbiotic partners, suggesting that nutrients themselves may serve as signals. This review summarizes our current knowledge on the early and late signal exchanges between woody plants and ECM fungi, and we suggest future directions for decoding the molecular basis of the underground dance between trees and their favorite fungal partners.


Via Kevin Garcia
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The role of community and population ecology in applying mycorrhizal fungi for improved food security

The role of community and population ecology in applying mycorrhizal fungi for improved food security | MycorWeb Plant-Microbe Interactions | Scoop.it
The global human population is expected to reach ~9 billion by 2050. Feeding this many people represents a major challenge requiring global crop yield increases of up to 100%. Microbial symbionts of plants such as arbuscular mycorrhizal fungi (AMF) represent a huge, but unrealized resource for improving yields of globally important crops, especially in the tropics. We argue that the application of AMF in agriculture is too simplistic and ignores basic ecological principals. To achieve this challenge, a community and population ecology approach can contribute greatly. First, ecologists could significantly improve our understanding of the determinants of the survival of introduced AMF, the role of adaptability and intraspecific diversity of AMF and whether inoculation has a direct or indirect effect on plant production. Second, we call for extensive metagenomics as well as population genomics studies that are crucial to assess the environmental impact that introduction of non-local AMF may have on native AMF communities and populations. Finally, we plead for an ecologically sound use of AMF in efforts to increase food security at a global scale in a sustainable manner.

Via Jean-Michel Ané, Pedobiologia: Journal of Soil Ecology
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Jean-Michel Ané's curator insight, April 21, 3:38 PM

Excellent review

Pedobiologia: Journal of Soil Ecology's curator insight, April 21, 6:33 PM

All are important questions to answer, but what about the question: what are the characteristics that make an AM fungus beneficial in an agricultural context? A trait-based approach would address this and some of the questions posed in the review.

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Contrasting Diversity and Host Association of Ectomycorrhizal Basidiomycetes versus Root-Associated Ascomycetes in a Dipterocarp Rainforest

Contrasting Diversity and Host Association of Ectomycorrhizal Basidiomycetes versus Root-Associated Ascomycetes in a Dipterocarp Rainforest | MycorWeb Plant-Microbe Interactions | Scoop.it
Root-associated fungi, including ectomycorrhizal and root-endophytic fungi, are among the most diverse and important belowground plant symbionts in dipterocarp rainforests. Our study aimed to reveal the biodiversity, host association, and community structure of ectomycorrhizal Basidiomycota and root-associated Ascomycota (including root-endophytic Ascomycota) in a lowland dipterocarp rainforest in Southeast Asia. The host plant chloroplast ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL) region and fungal internal transcribed spacer 2 (ITS2) region were sequenced using tag-encoded, massively parallel 454 pyrosequencing to identify host plant and root-associated fungal taxa in root samples. In total, 1245 ascomycetous and 127 putative ectomycorrhizal basidiomycetous taxa were detected from 442 root samples. The putative ectomycorrhizal Basidiomycota were likely to be associated with closely related dipterocarp taxa to greater or lesser extents, whereas host association patterns of the root-associated Ascomycota were much less distinct. The community structure of the putative ectomycorrhizal Basidiomycota was possibly more influenced by host genetic distances than was that of the root-associated Ascomycota. This study also indicated that in dipterocarp rainforests, root-associated Ascomycota were characterized by high biodiversity and indistinct host association patterns, whereas ectomycorrhizal Basidiomycota showed less biodiversity and a strong host phylogenetic preference for dipterocarp trees. Our findings lead to the working hypothesis that root-associated Ascomycota, which might be mainly represented by root-endophytic fungi, have biodiversity hotspots in the tropics, whereas biodiversity of ectomycorrhizal Basidiomycota increases with host genetic diversity.
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Evolution of mycoheterotrophy in Polygalaceae: The case of Epirixanthes

• Premise of the study: The mycoheterotrophic lifestyle has enabled some plant lineages to obtain carbon from their mycorrhizal symbionts. The mycoheterotrophic genus Epirixanthes (Polygalaceae) consists of six species from tropical Asia. Although it is probably closely related to the chlorophyllous genus Salomonia and linked to arbuscular mycorrhizal fungi, lack of DNA sequence data has thus far prevented these hypotheses from being tested. Therefore, the evolutionary history of Epirixanthes remains largely unknown.

• Methods: We reconstructed the phylogenetic relationships of Epirixanthesbased on nuclear ITS and plastid matK data. Divergence times were inferred using a Bayesian relaxed clock approach, and we phylogenetically analyzed its mycorrhizal symbionts. We furthermore assigned these symbionts to operational taxonomic units, compared them with symbionts of other Polygalaceae, and measured their phylogenetic diversity.

• Key results: We found that Epirixanthes is placed in tribe Polygaleae as sister to Salomonia. Epirixanthes has a Miocene-Oligocene stem age and grows exclusively in symbiosis with fungi of Glomeraceae. Salomonia and somePolygala species are linked to both Glomeraceae and Acaulosporaceae, resulting in higher phylogenetic diversity values. The majority of the symbionts of Epirixanthes are not found in Salomonia or Polygala, although a few shared fungal taxa are found.

• Conclusions: Epirixanthes forms a relatively young mycoheterotrophic lineage. The Oligocene-Miocene origin suggests its evolution was influenced by the environmental dynamics in Southeast Asia during this time. Although comparison of fungi from Epirixanthes with those from Salomonia and Polygalasuggests some specialization, many other mycoheterotrophic plants are linked to a more narrow set of Glomeraceae.


Via Pierre-Marc Delaux
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Anthropogenic environmental changes affect ecosystem stability via biodiversity

Anthropogenic environmental changes affect ecosystem stability via biodiversity | MycorWeb Plant-Microbe Interactions | Scoop.it
Human-driven environmental changes may simultaneously affect the biodiversity, productivity, and stability of Earth’s ecosystems, but there is no consensus on the causal relationships linking these variables. Data from 12 multiyear experiments that manipulate important anthropogenic drivers, including plant diversity, nitrogen, carbon dioxide, fire, herbivory, and water, show that each driver influences ecosystem productivity. However, the stability of ecosystem productivity is only changed by those drivers that alter biodiversity, with a given decrease in plant species numbers leading to a quantitatively similar decrease in ecosystem stability regardless of which driver caused the biodiversity loss. These results suggest that changes in biodiversity caused by drivers of environmental change may be a major factor determining how global environmental changes affect ecosystem stability.
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A symbiosis toolkit: Genetic analysis of mycorrhiza evolution

A symbiosis toolkit: Genetic analysis of mycorrhiza evolution | MycorWeb Plant-Microbe Interactions | Scoop.it
I wanted to write a bit more about my PhD and what I have been up to. However, I broke my knee 5 weeks ago playing rugby: rupturing two cruciate ligaments and fracturing my tibia… So I have been away from the lab. During an extended procrastination break I did however get chance to write this brief post, simplified to my level of understanding, about a recent Nature Genetics paper on the phylogenies of mycorrhizal fungi. 

Mycorrhizal fungi form key association with plants. They effectively extend the surface area of their hosts roots - the fungi supply the plant with nutrients such as nitrogen and phosphorus, in return, the plant supplies the fungi with carbon fixed by photosynthesis. This association is ubiquitous in higher plant species, where more than 80% have fungal partners. Thus exploring this relationship is crucial to understanding many ecological and evolutionary questions. 

Kohler et al.’s (2015) large scale study extended our knowledge of this plant-fungal association by delving into the evolution of mycorrhizal fungi. They compared fugal phylogenies of biotrophic (obtain carbon from plant hosts) and saprotrophic (carbon from degrading complex organic substrates) fungal genomes. This included studying 49 genomes of saprotrophs, ectomycorrhizal (ECM), orchid (ORM) and ericoid (ERM) species. Their comparison of these fungal genomes provides deeper understanding on how the plant-fungal association evolved and how this association aids the plant in adapting to its environment.

Via Jean-Michel Ané
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Invasion is sweet

Fungi are able to colonize almost any habitat and are famous for their capacity and efficiency to obtain nutrients from diverse sources. This efficiency also exists in plant pathogenic fungi that specialize in the degradation and uptake of plant-derived nutrients. Biotrophic fungi that parasitize living plants face particular challenges, since they not only need to keep the plant's immune systems in check but also compete with the plant for nutrients. Most biotrophic fungi develop particular feeding structures (so-called haustoria) that are formed within host cells and are thought to be necessary for feeding the parasite at the expense of the plant. Smut fungi do not form haustoria, which implies that they continuously fight their double war of immune evasion and nutrient theft without the support and comfort of a specialized feeding structure. In this issue of New Phytologist, Jörg Kämper and his group have now lifted the veil of how the maize smut fungus Ustilago maydis manages to sense and obtain sugars from its host plant during invasive growth (Schuler et al., pp. 1086–1100).
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Mycorrhizal networks and coexistence in species-rich orchid communities

Multispecies assemblages often consist of a complex network of interactions. Describing the architecture of these networks is a first step in understanding the stability and persistence of these species-rich communities. Whereas a large body of research has been devoted to the description of above-ground interactions, much less attention has been paid to below-ground interactions, probably because of difficulties to adequately assess the nature and diversity of interactions occurring below the ground.
In this study, we used 454 amplicon pyrosequencing to investigate the architecture of the network between mycorrhizal fungi and 20 orchid species co-occurring in a species-rich Mediterranean grasslands.
We found 100 different fungal operational taxonomic units (OTUs) known to be mycorrhizal in orchids, most of which were members related to the genera Ceratobasidium and Tulasnella. The network of interactions was significantly compartmentalized (M = 0.589, P = 0.001), but not significantly nested (N = 0.74, NODF = 10.58; P > 0.05). Relative nestedness was negative (N* = −0.014), also suggesting the existence of isolated groups of interacting species.
Compartmentalization is a typical feature of ecological systems showing high interaction intimacy, and may reflect strong specialization between orchids and fungi resulting from physiological, physical or spatial constraints
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Hxt1, a monosaccharide transporter and sensor required for virulence of the maize pathogen Ustilago maydis

The smut Ustilago maydis, a ubiquitous pest of corn, is highly adapted to its host to parasitize on its organic carbon sources. We have identified a hexose transporter, Hxt1, as important for fungal development during both the saprophytic and the pathogenic stage of the fungus.
Hxt1 was characterized as a high-affinity transporter for glucose, fructose, and mannose; ∆hxt1 strains show significantly reduced growth on these substrates, setting Hxt1 as the main hexose transporter during saprophytic growth.
After plant infection, ∆hxt1 strains show decreased symptom development. However, expression of a Hxt1 protein with a mutation leading to constitutively active signaling in the yeast glucose sensors Snf3p and Rgt2p results in completely apathogenic strains. Fungal development is stalled immediately after plant penetration, implying a dual function of Hxt1 as transporter and sensor.
As glucose sensors are only known for yeasts, ‘transceptor’ as Hxt1 may constitute a general mechanism for sensing of glucose in fungi. In U. maydis, Hxt1 links a nutrient-dependent environmental signal to the developmental program during pathogenic development.
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Evolving new organisms via symbiosis

Evolving new organisms via symbiosis | MycorWeb Plant-Microbe Interactions | Scoop.it
Symbiotic partnerships are a major source of evolutionary innovation. They have driven rapid diversification of organisms, allowed hosts to harness new forms of energy, and radically modified Earth's nutrient cycles. The application of next-generation sequencing and advanced microscopic techniques has revealed not only the ubiquity of symbiotic partnerships, but the extent to which partnerships can become physically, genomically, and metabolically integrated (1). When and why does this integration of once free-living organisms happen?
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Plant Cell: A Secreted Effector Protein of Ustilago maydis Guides Maize Leaf Cells to Form Tumors (2015)

Plant Cell: A Secreted Effector Protein of Ustilago maydis Guides Maize Leaf Cells to Form Tumors (2015) | MycorWeb Plant-Microbe Interactions | Scoop.it

The biotrophic smut fungus Ustilago maydis infects all aerial organs of maize (Zea mays) and induces tumors in the plant tissues. U. maydis deploys many effector proteins to manipulate its host. Previously, deletion analysis demonstrated that several effectors have important functions in inducing tumor expansion specifically in maize leaves. Here, we present the functional characterization of the effector See1 (Seedling efficient effector1). See1 is required for the reactivation of plant DNA synthesis, which is crucial for tumor progression in leaf cells. By contrast, See1 does not affect tumor formation in immature tassel floral tissues, where maize cell proliferation occurs independent of fungal infection. See1 interacts with a maize homolog of SGT1 (Suppressor of G2 allele of skp1), a factor acting in cell cycle progression in yeast (Saccharomyces cerevisiae) and an important component of plant and human innate immunity. See1 interferes with the MAPK-triggered phosphorylation of maize SGT1 at a monocot-specific phosphorylation site. We propose that See1 interferes with SGT1 activity, resulting in both modulation of immune responses and reactivation of DNA synthesis in leaf cells. This identifies See1 as a fungal effector that directly and specifically contributes to the formation of leaf tumors in maize.


Via Kamoun Lab @ TSL
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Characterization of the Carbohydrate Binding Module 18 gene family in the amphibian pathogen Batrachochytrium dendrobatidis

Characterization of the Carbohydrate Binding Module 18 gene family in the amphibian pathogen Batrachochytrium dendrobatidis | MycorWeb Plant-Microbe Interactions | Scoop.it
Batrachochytrium dendrobatidis (Bd) is the causative agent of chytridiomycosis responsible for worldwide decline in amphibian populations. Previous analysis of the Bd genome revealed a unique expansion of the carbohydrate-binding module family 18 (CBM18) predicted to be a sub-class of chitin recognition domains. CBM expansions have been linked to the evolution of pathogenicity in a variety of fungal species by protecting the fungus from the host. Based on phylogenetic analysis and presence of additional protein domains, the gene family can be classified into 3 classes: Tyrosinase-, Deacetylase-, and Lectin-like. Examination of the mRNA expression levels from sporangia and zoospores of nine of the cbm18 genes found that the Lectin-like genes had the highest expression while the Tyrosinase-like genes showed little expression, especially in zoospores. Heterologous expression of GFP-tagged copies of four CBM18 genes in Saccharomyces cerevisiae demonstrated that two copies containing secretion signal peptides are trafficked to the cell boundary. The Lectin-like genes cbm18-ll1 and cbm18-ll2 co-localized with the chitinous cell boundaries visualized by staining with calcofluor white. In vitro assays of the full length and single domain copies from CBM18-LL1 demonstrated chitin binding and no binding to cellulose or xylan. Expressed CBM18 domain proteins were demonstrated to protect the fungus, Trichoderma reeseii, in vitro against hydrolysis from exogenously added chitinase, likely by binding and limiting exposure of fungal chitin. These results demonstrate that cbm18 genes can play a role in fungal defense and expansion of their copy number may be an important pathogenicity factor of this emerging infectious disease of amphibians.
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The Top 10 oomycete pathogens in molecular plant pathology

The Top 10 oomycete pathogens in molecular plant pathology | MycorWeb Plant-Microbe Interactions | Scoop.it
Oomycetes form a deep lineage of eukaryotic organisms that includes a large number of plant pathogens which threaten natural and managed ecosystems. We undertook a survey to query the community for their ranking of plant-pathogenic oomycete species based on scientific and economic importance. In total, we received 263 votes from 62 scientists in 15 countries for a total of 33 species. The Top 10 species and their ranking are: (1) Phytophthora infestans; (2, tied) Hyaloperonospora arabidopsidis; (2, tied) Phytophthora ramorum; (4) Phytophthora sojae; (5) Phytophthora capsici; (6) Plasmopara viticola; (7) Phytophthora cinnamomi; (8, tied) Phytophthora parasitica; (8, tied) Pythium ultimum; and (10) Albugo candida. This article provides an introduction to these 10 taxa and a snapshot of current research. We hope that the list will serve as a benchmark for future trends in oomycete research.
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The role of symbiosis in the transition of some eukaryotes from aquatic to terrestrial environments

The role of symbiosis in the transition of some eukaryotes from aquatic to terrestrial environments | MycorWeb Plant-Microbe Interactions | Scoop.it
Symbiosis may have played a far greater role in biological evolution than was previously thought. The symbiosis that made the colonization of land by plants possible was as a consequence of the development of arbuscular mycorrhizae. However, the present review draws attention to the role of lichens in assisting in this transition and to the phenomenon of lichenization. The recent discovery of lichen fossils in marine phosphorites in China and molecular clock estimates indicate that lichenized fungi were already present in Precambrian seas and, like contemporary species, played a role as pioneers in occupying new habitats. There is evidence that the holistic properties of associations between fungi and cyanobacteria and/or green algae facilitated the transition onto land and the subsequent colonization of terrestrial habitats. A key role in this process was played by poikilohydry. The algal components of delichenized fungi, along with lichens and photosynthetic aquatic organisms all contributed to the increase in atmospheric oxygen. Lichens, fungi and cyanobacteria settling on land were undoubtedly important in the formation of soils and thereafter enhancing their fertility. It is suggested that vascular and other green plants were able grow on these primitive soils that were stabilized by the growth of lichens, algae and cyanobacteria in a similar way to those which play a role in desert crusts at the present time.

Via Jean-Michel Ané, Pedobiologia: Journal of Soil Ecology
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Self-DNA: a blessing in disguise?

Self-DNA: a blessing in disguise? | MycorWeb Plant-Microbe Interactions | Scoop.it
Mazzoleni et al. (2015a,b) in two recent papers provided novel and rigorous evidence for a unique detrimental effect of self-DNA (i.e. DNA originating from conspecifics) on organismal growth. The authors investigated the effect as a means of explaining plant–soil feedbacks via plant litter (Mazzoleni et al., 2015a) and subsequently convincingly generalized their observations to a range of additional organisms including protozoa, algae, fungi and animals. The authors explain the growth suppression on the basis of inhibitory effects of self-DNA. They argue that this inhibition mechanism, through facilitating coexistence, represents a mechanism of maintaining diversity. The ecological, physiological and molecular significance of the observations of Mazzoleni et al. (2015a,b) is thought-provoking. A priority now is to start a discourse on the interpretation of the results of these studies, because this will help design focused experiments to further investigate the role of self-DNA on growth.
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Jean-Michel Ané's curator insight, April 21, 9:45 AM
That's really a provoking idea indeed...
Pedobiologia: Journal of Soil Ecology's curator insight, April 21, 6:15 PM

Can self-DNA act as a signal of conspecific density? An excellent and contextual mechanistic proposal.

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Global Genome and Transcriptome Analyses of Magnaporthe oryzae Epidemic Isolate 98-06 Uncover Novel Effectors and Pathogenicity-Related Genes, Revealing Gene Gain and Lose Dynamics in Genome Evol...

Global Genome and Transcriptome Analyses of  Magnaporthe oryzae  Epidemic Isolate 98-06 Uncover Novel Effectors and Pathogenicity-Related Genes, Revealing Gene Gain and Lose Dynamics in Genome Evol... | MycorWeb Plant-Microbe Interactions | Scoop.it
Genome dynamics of pathogenic organisms are driven by pathogen and host co-evolution, in which pathogen genomes are shaped to overcome stresses imposed by hosts with various genetic backgrounds through generation of a variety of isolates. This same principle applies to the rice blast pathogen Magnaporthe oryzae and the rice host; however, genetic variations among different isolates of M. oryzae remain largely unknown, particularly at genome and transcriptome levels. Here, we applied genomic and transcriptomic analytical tools to investigate M. oryzae isolate 98-06 that is the most aggressive in infection of susceptible rice cultivars. A unique 1.4 Mb of genomic sequences was found in isolate 98-06 in comparison to reference strain 70-15. Genome-wide expression profiling revealed the presence of two critical expression patterns of M. oryzae based on 64 known pathogenicity-related (PaR) genes. In addition, 134 candidate effectors with various segregation patterns were identified. Five tested proteins could suppress BAX-mediated programmed cell death in Nicotiana benthamiana leaves. Characterization of isolate-specific effector candidates Iug6 and Iug9 and PaR candidate Iug18 revealed that they have a role in fungal propagation and pathogenicity. Moreover, Iug6 and Iug9 are located exclusively in the biotrophic interfacial complex (BIC) and their overexpression leads to suppression of defense-related gene expression in rice, suggesting that they might participate in biotrophy by inhibiting the SA and ET pathways within the host. Thus, our studies identify novel effector and PaR proteins involved in pathogenicity of the highly aggressive M. oryzae field isolate 98-06, and reveal molecular and genomic dynamics in the evolution of M. oryzae and rice host interactions.
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Evolutionary innovation and ecology in marine tetrapods from the Triassic to the Anthropocene

Evolutionary innovation and ecology in marine tetrapods from the Triassic to the Anthropocene | MycorWeb Plant-Microbe Interactions | Scoop.it

Many top consumers in today’s oceans are marine tetrapods, a collection of lineages independently derived from terrestrial ancestors. The fossil record illuminates their transitions from land to sea, yet these initial invasions account for a small proportion of their evolutionary history. We review the history of marine invasions that drove major changes in anatomy, physiology, and ecology over more than 250 million years. Many innovations evolved convergently in multiple clades, whereas others are unique to individual lineages. The evolutionary arcs of these ecologically important clades are framed against the backdrop of mass extinctions and regime shifts in ocean ecosystems. Past and present human disruptions to marine tetrapods, with cascading impacts on marine ecosystems, underscore the need to link macroecology with evolutionary change.

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Full Establishment of Arbuscular Mycorrhizal Symbiosis in Rice Occurs Independently of Enzymatic Jasmonate Biosynthesis

Full Establishment of Arbuscular Mycorrhizal Symbiosis in Rice Occurs Independently of Enzymatic Jasmonate Biosynthesis | MycorWeb Plant-Microbe Interactions | Scoop.it
Development of the mutualistic arbuscular mycorrhiza (AM) symbiosis between most land plants and fungi of the Glomeromycota is regulated by phytohormones. The role of jasmonate (JA) in AM colonization has been investigated in the dicotyledons Medicago truncatula, tomato and Nicotiana attenuata and contradicting results have been obtained with respect to a neutral, promotive or inhibitory effect of JA on AM colonization. Furthermore, it is currently unknown whether JA plays a role in AM colonization of monocotyledonous roots. Therefore we examined whether JA biosynthesis is required for AM colonization of the monocot rice. To this end we employed the rice mutant constitutive photomorphogenesis 2 (cpm2), which is deficient in JA biosynthesis. Through a time course experiment the amount and morphology of fungal colonization did not differ between wild-type and cpm2 roots. Furthermore, no significant difference in the expression of AM marker genes was detected between wild type and cpm2. However, treatment of wild-type roots with 50 μM JA lead to a decrease of AM colonization and this was correlated with induction of the defense gene PR4. These results indicate that JA is not required for AM colonization of rice but high levels of JA in the roots suppress AM development likely through the induction of defense.

Via Jean-Michel Ané
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Jean-Michel Ané's curator insight, April 12, 11:22 AM

I am so glad that PLoS ONE allows to publish such "negative results" because they are very important too. I am not sure that this could have been published in more conventional journals.

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Laccaria bicolor Aquaporin LbAQP1 is required for Hartig Net Development in Trembling Aspen (Populus tremuloides) - NAVARRO-RÓDENAS - Plant, Cell & Environment - Wiley Online Library

Laccaria bicolor Aquaporin LbAQP1 is required for Hartig Net Development in Trembling Aspen (Populus tremuloides) - NAVARRO-RÓDENAS - Plant, Cell & Environment - Wiley Online Library | MycorWeb Plant-Microbe Interactions | Scoop.it

The development of ectomycorrhizal associations is crucial for growth of many forest trees. However, the signals that are exchanged between the fungus and the host plant during the colonization process are still poorly understood. In this study, we have identified the relationship between expression patterns of Laccaria bicolor aquaporin LbAQP1 and the development of ectomycorrhizal structures in trembling aspen (Populus tremuloides) seedlings. The peak expression of LbAQP1 was 700-fold higher in the hyphae within the root than in the free-living mycelium after 24 h of direct interaction with the roots. Moreover, in LbAQP1 knock-down strains, a non-mycorrhizal phenotype was developed without the Hartig net and the expression of the mycorrhizal effector protein MiSSP7 quickly declined after an initial peak on day 5 of interaction of the fungal hyphae with the roots. The increase in the expression of LbAQP1 required a direct contact of the fungus with the root and it modulated the expression of MiSSP7. We have also determined that LbAQP1 facilitated NO, H2O2 and CO2 transport when heterologously expressed in yeast. The report demonstrates that the Laccaria bicolor aquaporin LbAQP1 acts as a molecular signaling channel, which is fundamental for the development of Hartig net in root tips of Populus tremuloides.


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Strong altitudinal partitioning in the distributions of ectomycorrhizal fungi along a short (300 m) elevation gradient

Changes in species richness and distributions of ectomycorrhizal (ECM) fungal communities along altitudinal gradients have been attributed to changes in both host distributions and abiotic variables. However, few studies have considered altitudinal relationships of ECM fungi associated with a single host to identify the role of abiotic drivers. To address this, ECM fungal communities associated with one host were assessed along five altitudinal transects in Scotland.
Roots of Scots pine (Pinus sylvestris) were collected from sites between 300 and 550–600 m altitude, and ECM fungal communities were identified by 454 pyrosequencing of the fungal internal transcribed spacer (ITS) region. Soil moisture, temperature, pH, carbon : nitrogen (C : N) ratio and organic matter content were measured as potential predictors of fungal species richness and community composition.
Altitude did not affect species richness of ECM fungal communities, but strongly influenced fungal community composition. Shifts in community composition along the altitudinal gradient were most clearly related to changes in soil moisture and temperature.
Our results show that a 300 m altitudinal gradient produced distinct shifts in ECM fungal communities associated with a single host, and that this pattern was strongly related to climatic variables. This finding suggests significant climatic niche partitioning among ECM fungal species.
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Jean-Michel Ané's curator insight, April 11, 12:44 PM

Very interesting

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The fungal core effector Pep1 is conserved across smuts of dicots and monocots

The secreted fungal effector Pep1 is essential for penetration of the host epidermis and establishment of biotrophy in the Ustilago maydis–maize pathosystem. Previously, Pep1 was found to be an inhibitor of apoplastic plant peroxidases, which suppresses the oxidative burst, a primary immune response of the host plant and enables fungal colonization.
To investigate the conservation of Pep1 in other pathogens, genomes of related smut species were screened for pep1 orthologues. Pep1 proteins were produced in Escherichia coli for functional assays. The biological function of Pep1 was tested by heterologous expression in U. maydis and Hordeum vulgare.
Pep1 orthologues revealed a remarkable degree of sequence conservation, indicating that this effector might play a fundamental role in virulence of biotrophic smut fungi. Pep1 function and its role in virulence are conserved in different pathogenic fungi, even across the monocot–dicot border of host plants.
The findings described in this study classify Pep1 as a phylogenetically conserved fungal core effector. Furthermore, we documented the influence of Pep1 on the disease caused by Blumeria graminis f. sp. hordei which is a non-smut-related pathosystem.
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