MycorWeb Plant-Microbe Interactions
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MycorWeb Plant-Microbe Interactions
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A multi-omic future for microbiome studies

A multi-omic future for microbiome studies | MycorWeb Plant-Microbe Interactions | Scoop.it
Integration of multiple ‘omics’ technologies will allow researchers to gain a more complete picture of the constituents and functions of microbial communities and provide far richer information for predictive modelling of community phenotypes.
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New mutualistic fungal endophytes isolated from poplar roots display high metal tolerance

New mutualistic fungal endophytes isolated from poplar roots display high metal tolerance | MycorWeb Plant-Microbe Interactions | Scoop.it
This study aimed to isolate, identify, and characterise metal-tolerant fungi colonising poplar roots at a metal-contaminated phytoremediation site. Poplar roots were colonised by arbuscular mycorrhizal, ectomycorrhizal, and endophytic fungi, and the species were determined by ITS molecular analyses. Eight different isolates were successfully isolated into pure culture. Three isolates belonging to the Helotiales (P02, P06) and the Serendipita vermifera species (P04) were highly tolerant to metals (Cd, Zn, Pb, and Cu) compared to the mycorrhizal Hebeloma isolates. The three isolates degraded complex carbohydrates, such as xylan and cellulose, indicating that they could partially degrade root cell walls and penetrate into cells. This hypothesis was confirmed by further in vitro re-synthesis experiments, which showed that the three isolates colonised root tissues of poplar plantlets whereas two of them formed microsclerotia-like structures. Taken together, these results suggest an endophytic lifestyle of these isolates. This is the first evidence of S. vermifera as a root endophyte of poplar. A new endophytic putative species belonging to the Helotiales and closely related to Leohumicola is also reported. Interestingly, and when compared to mock-inoculated plants, both P06 and P04 isolates increased the number of root tips of inoculated poplar plantlets in vitro. Moreover, the S. vermifera P04 isolate also increased the shoot biomass. The results are discussed in relation to the potential use of endophytic strains for tree-based phytoremediation of metal-contaminated sites.

Via Jean-Michel Ané
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Rapid cloning of disease-resistance genes in plants using mutagenesis and sequence capture

Rapid cloning of disease-resistance genes in plants using mutagenesis and sequence capture | MycorWeb Plant-Microbe Interactions | Scoop.it
Wild relatives of domesticated crop species harbor multiple, diverse, disease resistance (R) genes that could be used to engineer sustainable disease control. However, breeding R genes into crop lines often requires long breeding timelines of 5–15 years to break linkage between R genes and deleterious alleles (linkage drag). Further, when R genes are bred one at a time into crop lines, the protection that they confer is often overcome within a few seasons by pathogen evolution1. If several cloned R genes were available, it would be possible to pyramid R genes2 in a crop, which might provide more durable resistance1. We describe a three-step method (MutRenSeq)-that combines chemical mutagenesis with exome capture and sequencing for rapid R gene cloning. We applied MutRenSeq to clone stem rust resistance genes Sr22 and Sr45 from hexaploid bread wheat. MutRenSeq can be applied to other commercially relevant crops and their relatives, including, for example, pea, bean, barley, oat, rye, rice and maize.
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Effector-Mining in the Poplar Rust Fungus Melampsora larici-populina Secretome

Effector-Mining in the Poplar Rust Fungus Melampsora larici-populina Secretome | MycorWeb Plant-Microbe Interactions | Scoop.it
The poplar leaf rust fungus, Melampsora larici-populina has been established as a tree-microbe interaction model. Understanding the molecular mechanisms controlling infection by pathogens appears essential for durable management of tree plantations. In biotrophic plant-parasites, effectors are known to condition host cell colonization. Thus, investigation of candidate secreted effector proteins (CSEPs) is a major goal in the poplar–poplar rust interaction. Unlike oomycetes, fungal effectors do not share conserved motifs and candidate prediction relies on a set of a priori criteria established from reported bona fide effectors. Secretome prediction, genome-wide analysis of gene families and transcriptomics of M. larici-populina have led to catalogs of more than a thousand secreted proteins. Automatized effector-mining pipelines hold great promise for rapid and systematic identification and prioritization of CSEPs for functional characterization. In this review, we report on and discuss the current status of the poplar rust fungus secretome and prediction of candidate effectors from this species.
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Transcriptome analysis of poplar rust telia reveals overwintering adaptation and tightly coordinated karyogamy and meiosis processes

Transcriptome analysis of poplar rust telia reveals overwintering adaptation and tightly coordinated karyogamy and meiosis processes | MycorWeb Plant-Microbe Interactions | Scoop.it
Most rust fungi have a complex life cycle involving up to five different spore-producing stages. The telial stage that produces melanized overwintering teliospores is one of these and plays a fundamental role for generating genetic diversity as karyogamy and meiosis occur at that stage. Despite the importance of telia for the rust life cycle, almost nothing is known about the fungal genetic programs that are activated in this overwintering structure. In the present study, the transcriptome of telia produced by the poplar rust fungus Melampsora larici-populina has been investigated using whole genome exon oligoarrays and RT-qPCR. Comparative expression profiling at the telial and uredinial stages identifies genes specifically expressed or up-regulated in telia including osmotins/thaumatin-like proteins (TLPs) and aquaporins that may reflect specific adaptation to overwintering as well numerous lytic enzymes acting on plant cell wall, reflecting extensive cell wall remodeling at that stage. The temporal dynamics of karyogamy was followed using combined RT-qPCR and DAPI-staining approaches. This reveals that fusion of nuclei and induction of karyogamy-related genes occur simultaneously between the 25 and 39 days post inoculation time frame. Transcript profiling of conserved meiosis genes indicates a preferential induction right after karyogamy and corroborates that meiosis begins prior to overwintering and is interrupted in Meiosis I (prophase I, diplonema stage) until teliospore germination in early spring.
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Genomics Research on Non-model Plant Pathogens: Delivering Novel Insights into Rust Fungus Biology

The diversity among rust fungi is simply astounding: over 7000 species that evolved to colonize niches all over the plant kingdom. This diversification likely involved major host jumps, especially considering that the life cycles of heteroecious rusts, such as the cereal rusts, involve sexual and asexual stages that take place on completely unrelated host plants (Savile, 1976; McTaggart et al., 2015), but also co-evolution in diverse natural settings, establishing equilibrium (e.g., Thrall et al., 2012). These interactions resulted in complex life styles including for many rusts, the production of up to five different spore types, each requiring very different developmental programs and hence gene expression.

Unfortunately, despite the intriguing biology of these fascinating pathogens, many rust fungi have gained notoriety because of the fact that some of their hosts were selected as food sources by humans leading to their extensive cultivation, and more recently their monocultures over large areas. Upsetting the balance, the rust fungi took the occasion, having a ball.

Because of their importance, plenty of research has been done on rust fungi describing life cycles, host range, and infection processes. Driven by the need for resistant crop cultivars, the genetics of race-cultivar interactions and fungal race identification pioneered in the 1940's, became the staple for breeding programs worldwide. However, because of their strict biotrophic life styles and recalcitrance to genetic transformation, molecular genetic research on rust fungi remains difficult. The advance of genomics has really impacted research on rust fungi, demonstrated by the expansion of labs embarking on and receiving funding for molecular work over the last 5 years. With this in mind, we invited submissions for this Frontiers in Plant Science Research Topic and present here 14 papers.
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Biological control of tree and woody plant diseases: an impossible task?

Biological control of tree and woody plant diseases: an impossible task? | MycorWeb Plant-Microbe Interactions | Scoop.it
The social demand for novel, sustainable and environment friendly approaches, while ensuring the health and productivity of our crops, is increasingly growing. Research on biological control of tree/woody crop diseases is scarce compared to that conducted on herbaceous, annual plants. In addition to their large biomass, complicated anatomy, longevity and perennial nature, peculiarities in the management of tree crops and forestry also contribute to the complexity of the processes of developing effective biological control measures in these agro-ecosystems. Although biological control in woody species poses challenges, difficulties and limitations, its implementation either alone or in combination with other disease management strategies is feasible. As a result, examples of successful application of biocontrol measures based on the use of bacteria, fungi or hypovirulent mycoviruses against tree/woody plant diseases are available. The aim of this special issue is to provide interested readers with an overview and updates on the active research field of biological control of tree and woody plant diseases. Such effort includes updates ranging from the generation of fundamental knowledge to examples of successful application of biological control strategies.

Via Jean-Michel Ané
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First evidence for truffle production from plants inoculated with mycelial pure cultures

First evidence for truffle production from plants inoculated with mycelial pure cultures | MycorWeb Plant-Microbe Interactions | Scoop.it
Truffle (Tuber spp.) cultivation is based on raising mycorrhizal trees in greenhouses that have been inoculated with suspensions of ascospores. The problem with this is that pests, pathogens, and other mycorrhizal fungi can contaminate the trees. Furthermore, because ascospores are produced sexually, each plant potentially has a different genetic mycorrhizal makeup from each other so tailoring the mycorrhizal component of plants to suit a particular set of soil and climatic conditions is out of the question. Here, we report on the production of Tuber borchii-mycorrhized plants using pure cultures, establishing a truffière with these and subsequent production of its fruiting bodies. This study opens up the possibility of producing commercial numbers of Tuber-mycorrhized trees for truffle cultivation using mycelial inoculation techniques. It also poses questions about the mechanism of fertilization between the different strains which were located in different parts of the experimental truffière.

Via Jean-Michel Ané
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Nuclear dynamics and genetic rearrangement in heterokaryotic colonies of Fusarium oxysporum

Nuclear dynamics and genetic rearrangement in heterokaryotic colonies of Fusarium oxysporum | MycorWeb Plant-Microbe Interactions | Scoop.it
Recent studies have shown horizontal transfer of chromosomes to be a potential key contributor to genome plasticity in asexual fungal pathogens. However, the mechanisms behind horizontal chromosome transfer in eukaryotes are not well understood. Here we investigated the role of conidial anastomosis in heterokaryon formation between incompatible strains of Fusarium oxysporum and determined the importance of heterokaryons for horizontal chromosome transfer. Using live-cell imaging we demonstrate that conidial pairing of incompatible strains under carbon starvation can result in the formation of viable heterokaryotic hyphae in F. oxysporum. Nuclei of the parental lines presumably fuse at some stage as conidia with a single nucleus harboring both marker histones (GFP- and RFP-tagged) are produced. Upon colony formation, this hybrid offspring is subject to progressive and gradual genome rearrangement. The parental genomes appear to become spatially separated and RFP-tagged histones, deriving from one of the strains, Fol4287, are eventually lost. With a PCR-based method we showed that markers for most of the chromosomes of this strain are lost, indicating a lack of Fol4287 chromosomes. This leaves offspring with the genomic background of the other strain (Fo47), but in some cases together with one or two chromosomes from Fol4287, including the chromosome that confers pathogenicity towards tomato.

Via Alejandro Rojas
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Community assembly and coexistence in communities of arbuscular mycorrhizal fungi

Community assembly and coexistence in communities of arbuscular mycorrhizal fungi | MycorWeb Plant-Microbe Interactions | Scoop.it
Arbuscular mycorrhizal fungi are asexual, obligately symbiotic fungi with unique morphology and genomic structure, which occupy a dual niche, that is, the soil and the host root. Consequently, the direct adoption of models for community assembly developed for other organism groups is not evident. In this paper we adapted modern coexistence and assembly theory to arbuscular mycorrhizal fungi. We review research on the elements of community assembly and coexistence of arbuscular mycorrhizal fungi, highlighting recent studies using molecular methods. By addressing several points from the individual to the community level where the application of modern community ecology terms runs into problems when arbuscular mycorrhizal fungi are concerned, we aim to account for these special circumstances from a mycocentric point of view. We suggest that hierarchical spatial structure of arbuscular mycorrhizal fungal communities should be explicitly taken into account in future studies. The conceptual framework we develop here for arbuscular mycorrhizal fungi is also adaptable for other host-associated microbial communities.
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Sequence variation in nuclear ribosomal SSU, ITS and LSU regions of Rhizophagus irregularis and Gigaspora margarita is high and isolate-dependent

Sequence variation in nuclear ribosomal SSU, ITS and LSU regions of Rhizophagus irregularis and Gigaspora margarita is high and isolate-dependent | MycorWeb Plant-Microbe Interactions | Scoop.it
Arbuscular mycorrhizal fungi are known to exhibit high intra-organism genetic variation. However, information about intra- vs interspecific variation among the genes commonly used in diversity surveys is limited.

Here, the nuclear small subunit (SSU) rRNA gene, Internal Transcribed Spacer (ITS) region, and large subunit (LSU) rRNA gene portions were sequenced from three to five individual spores from each of two isolates of Rhizophagus irregularis and Gigaspora margarita. A total of 1482 Sanger sequences (0.5Mb) from 239 clones were obtained, spanning c. 4370 bp of the ribosomal operon when concatenated.

Intra-sporal and intra-isolate sequence variation was high for all three regions even though variant numbers were not exhausted by sequencing 12 to 40 clones per isolate. Intra-isolate nucleotide variation levels followed the expected order of ITS>LSU>SSU, but the values were strongly dependent on isolate identity. SNP densities over 4 SNP/kb in the ribosomal operon were detected in all four isolates. Automated OTU-picking within the sequence set of known identity overestimated species richness with almost all cutoff levels, markers and isolates. Average intraspecific sequence similarity values were 99%, 96% and 94% for amplicons in SSU, LSU and ITS respectively.

The suitability of the central part of the SSU as a marker for arbuscular mycorrhizal fungal community surveys was further supported by its level of nucleotide variation, which is similar to that of the ITS region; its alignability across the entire phylum; its appropriate length for next generation sequencing; and its ease of amplification in single-step PCR.
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In situ imaging reveals the biomass of giant protists in the global ocean : Nature

In situ imaging reveals the biomass of giant protists in the global ocean : Nature | MycorWeb Plant-Microbe Interactions | Scoop.it
Planktonic organisms play crucial roles in oceanic food webs and global biogeochemical cycles1, 2. Most of our knowledge about the ecological impact of large zooplankton stems from research on abundant and robust crustaceans, and in particular copepods3, 4. A number of the other organisms that comprise planktonic communities are fragile, and therefore hard to sample and quantify, meaning that their abundances and effects on oceanic ecosystems are poorly understood. Here, using data from a worldwide in situ imaging survey of plankton larger than 600 μm, we show that a substantial part of the biomass of this size fraction consists of giant protists belonging to the Rhizaria, a super-group of mostly fragile unicellular marine organisms that includes the taxa Phaeodaria and Radiolaria (for example, orders Collodaria and Acantharia). Globally, we estimate that rhizarians in the top 200 m of world oceans represent a standing stock of 0.089 Pg carbon, equivalent to 5.2% of the total oceanic biota carbon reservoir5. In the vast oligotrophic intertropical open oceans, rhizarian biomass is estimated to be equivalent to that of all other mesozooplankton (plankton in the size range 0.2–20 mm). The photosymbiotic association of many rhizarians with microalgae may be an important factor in explaining their distribution. The previously overlooked importance of these giant protists across the widest ecosystem on the planet6 changes our understanding of marine planktonic ecosystems.
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Understanding plant cell-wall remodelling during the symbiotic interaction between Tuber melanosporum and Corylus avellana using a carbohydrate microarray - Online First - Springer

Understanding plant cell-wall remodelling during the symbiotic interaction between Tuber melanosporum and Corylus avellana using a carbohydrate microarray - Online First - Springer | MycorWeb Plant-Microbe Interactions | Scoop.it
Main conclusion

A combined approach, using a carbohydrate microarray as a support for genomic data, has revealed subtle plant cell-wall remodelling during Tuber melanosporum and Corylus avellana interaction.

Cell walls are involved, to a great extent, in mediating plant–microbe interactions. An important feature of these interactions concerns changes in the cell-wall composition during interaction with other organisms. In ectomycorrhizae, plant and fungal cell walls come into direct contact, and represent the interface between the two partners. However, very little information is available on the re-arrangement that could occur within the plant and fungal cell walls during ectomycorrhizal symbiosis. Taking advantage of the Comprehensive Microarray Polymer Profiling (CoMPP) technology, the current study has had the aim of monitoring the changes that take place in the plant cell wall in Corylus avellana roots during colonization by the ascomycetous ectomycorrhizal fungus T. melanosporum. Additionally, genes encoding putative plant cell-wall degrading enzymes (PCWDEs) have been identified in the T. melanosporum genome, and RT-qPCRs have been performed to verify the expression of selected genes in fully developed C. avellana/T. melanosporum ectomycorrhizae. A localized degradation of pectin seems to occur during fungal colonization, in agreement with the growth of the ectomycorrhizal fungus through the middle lamella and with the fungal gene expression of genes acting on these polysaccharides.

Via Christophe Jacquet
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Plant protein behaves like a prion

Plant protein behaves like a prion | MycorWeb Plant-Microbe Interactions | Scoop.it
Prions, the misfolded proteins that are known for causing degenerative illnesses in animals and humans, may have been spotted for the first time in plants.

Researchers led by Susan Lindquist, a biologist at the Whitehead Institute for Biomedical Research in Cambridge, Massachusetts, report that they have found a section of protein in thale cress (Arabidopsis) that behaves like a prion when it is inserted into yeast.
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Accelerated cloning of a potato late blight-resistance gene using RenSeq and SMRT sequencing

Accelerated cloning of a potato late blight-resistance gene using RenSeq and SMRT sequencing | MycorWeb Plant-Microbe Interactions | Scoop.it
Global yields of potato and tomato crops have fallen owing to potato late blight disease, which is caused by Phytophthora infestans. Although most commercial potato varieties are susceptible to blight, many wild potato relatives show variation for resistance and are therefore a potential source of Resistance to P. infestans (Rpi) genes. Resistance breeding has exploited Rpi genes from closely related tuber-bearing potato relatives, but is laborious and slow1, 2, 3. Here we report that the wild, diploid non-tuber-bearing Solanum americanum harbors multiple Rpi genes. We combine resistance (R) gene sequence capture (RenSeq)4 with single-molecule real-time (SMRT) sequencing (SMRT RenSeq) to clone Rpi-amr3i. This technology should enable de novo assembly of complete nucleotide-binding, leucine-rich repeat receptor (NLR) genes, their regulatory elements and complex multi-NLR loci from uncharacterized germplasm. SMRT RenSeq can be applied to rapidly clone multiple R genes for engineering pathogen-resistant crops
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A symbiosis-dedicated SYNTAXIN OF PLANTS 13II isoform controls the formation of a stable host–microbe interface in symbiosis

Arbuscular mycorrhizal (AM) fungi and rhizobium bacteria are accommodated in specialized membrane compartments that form a host–microbe interface. To better understand how these interfaces are made, we studied the regulation of exocytosis during interface formation. We used a phylogenetic approach to identify target soluble N-ethylmaleimide-sensitive factor-attachment protein receptors (t-SNAREs) that are dedicated to symbiosis and used cell-specific expression analysis together with protein localization to identify t-SNAREs that are present on the host–microbe interface in Medicago truncatula. We investigated the role of these t-SNAREs during the formation of a host–microbe interface. We showed that multiple syntaxins are present on the peri-arbuscular membrane. From these, we identified SYNTAXIN OF PLANTS 13II (SYP13II) as a t-SNARE that is essential for the formation of a stable symbiotic interface in both AM and rhizobium symbiosis. In most dicot plants, the SYP13II transcript is alternatively spliced, resulting in two isoforms, SYP13IIα and SYP13IIβ. These splice-forms differentially mark functional and degrading arbuscule branches. Our results show that vesicle traffic to the symbiotic interface is specialized and required for its maintenance. Alternative splicing of SYP13II allows plants to replace a t-SNARE involved in traffic to the plasma membrane with a t-SNARE that is more stringent in its localization to functional arbuscules.

Via Pierre-Marc Delaux
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On the current status of Phakopsora pachyrhizi genome sequencing

On the current status of Phakopsora pachyrhizi genome sequencing | MycorWeb Plant-Microbe Interactions | Scoop.it
Recent advances in the field of sequencing technologies and bioinformatics allow a more rapid access to genomes of non-model organisms at sinking costs. Accordingly, draft genomes of several economically important cereal rust fungi have been released in the last 3 years. Aside from the very recent flax rust and poplar rust draft assemblies there are no genomic data available for other dicot-infecting rust fungi. In this article we outline rust fungus sequencing efforts and comment on the current status of Phakopsora pachyrhizi (Asian soybean rust) genome sequencing.
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Genome-wide patterns of segregation and linkage disequilibrium: the construction of a linkage genetic map of the poplar rust fungus Melampsora larici-populina

Genome-wide patterns of segregation and linkage disequilibrium: the construction of a linkage genetic map of the poplar rust fungus Melampsora larici-populina | MycorWeb Plant-Microbe Interactions | Scoop.it
The poplar rust fungus Melampsora larici-populina causes significant yield reduction and severe economic losses in commercial poplar plantations. After several decades of breeding for qualitative resistance and subsequent breakdown of the released resistance genes, breeders now focus on quantitative resistance, perceived to be more durable. But quantitative resistance also can be challenged by an increase of aggressiveness in the pathogen. Thus, it is of primary importance to better understand the genetic architecture of aggressiveness traits. To this aim, our goal is to build a genetic linkage map for M. larici-populina in order to map quantitative trait loci related to aggressiveness. First, a large progeny of M. larici-populina was generated through selfing of the reference strain 98AG31 (which genome sequence is available) on larch plants, the alternate host of the poplar rust fungus. The progeny's meiotic origin was validated through a segregation analysis of 115 offspring with 14 polymorphic microsatellite markers, of which 12 segregated in the expected 1:2:1 Mendelian ratio. A microsatellite-based linkage disequilibrium analysis allowed us to identify one potential linkage group comprising two scaffolds. The whole genome of a subset of 47 offspring was resequenced using the Illumina HiSeq 2000 technology at a mean sequencing depth of 6X. The reads were mapped onto the reference genome of the parental strain and 144,566 SNPs were identified across the genome. Analysis of distribution and polymorphism of the SNPs along the genome led to the identification of 2580 recombination blocks. A second linkage disequilibrium analysis, using the recombination blocks as markers, allowed us to group 81 scaffolds into 23 potential linkage groups. These preliminary results showed that a high-density linkage map could be constructed by using high-quality SNPs based on low-coverage resequencing of a larger number of M. larici-populina offspring.
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The Cacti Microbiome: Interplay between Habitat-Filtering and Host-Specificity

The Cacti Microbiome: Interplay between Habitat-Filtering and Host-Specificity | MycorWeb Plant-Microbe Interactions | Scoop.it
Cactaceae represents one of the most species-rich families of succulent plants native to arid and semi-arid ecosystems, yet the associations Cacti establish with microorganisms and the rules governing microbial community assembly remain poorly understood. We analyzed the composition, diversity, and factors influencing above- and below-ground bacterial, archaeal, and fungal communities associated with two native and sympatric Cacti species: Myrtillocactus geometrizans and Opuntia robusta. Phylogenetic profiling showed that the composition and assembly of microbial communities associated with Cacti were primarily influenced by the plant compartment; plant species, site, and season played only a minor role. Remarkably, bacterial, and archaeal diversity was higher in the phyllosphere than in the rhizosphere of Cacti, while the opposite was true for fungi. Semi-arid soils exhibited the highest levels of microbial diversity whereas the stem endosphere the lowest. Despite their taxonomic distance, M. geometrizans and O. robusta shared most microbial taxa in all analyzed compartments. Influence of the plant host did only play a larger role in the fungal communities of the stem endosphere. These results suggest that fungi establish specific interactions with their host plant inside the stem, whereas microbial communities in the other plant compartments may play similar functional roles in these two species. Biochemical and molecular characterization of seed-borne bacteria of Cacti supports the idea that these microbial symbionts may be vertically inherited and could promote plant growth and drought tolerance for the fitness of the Cacti holobiont. We envision this knowledge will help improve and sustain agriculture in arid and semi-arid regions of the world.
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Molecular cloning and functional analysis of two phosphate transporter genes from Rhizopogon luteolus and Leucocortinarius bulbiger , two ectomycorrhizal fungi of Pinus tabulaeformis

Molecular cloning and functional analysis of two phosphate transporter genes from Rhizopogon luteolus and Leucocortinarius bulbiger , two ectomycorrhizal fungi of Pinus tabulaeformis | MycorWeb Plant-Microbe Interactions | Scoop.it
Inorganic phosphorus (Pi) is essential for plant growth, and phosphate (P) deficiency is a primary limiting factor in Pinus tabulaeformis development in northern China. P acquisition in mycorrhizal plants is highly dependent on the activities of phosphate transporters of their root-associated fungi. In the current study, two phosphate transporter genes, RlPT and LbPT, were isolated from Rhizopogon luteolus and Leucocortinarius bulbiger, respectively, two ectomycorrhizal fungi forming symbiotic interactions with the P. tabulaeformis. Phylogenetic analysis suggested that the sequence of the phosphate transporter of L. bulbiger is most closely related to a phosphate transporter of Hebeloma cylindrosporum, whereas the phosphate transporter of R. luteolus is most closely related to that of Piloderma croceum. The subcellular localization indicated that RlPT and LbPT were expressed in the plasma membrane. The complementation assay in yeast indicated that both RlPT and LbPT partially compensated for the absence of phosphate transporter activity in the MB192 yeast strain, with a K m value of 57.90 μmol/L Pi for RlPT and 35.87 μmol/L Pi for LbPT. qPCR analysis revealed that RlPT and LbPT were significantly up-regulated at lower P availability, which may enhance P uptake and transport under Pi starvation. Our results suggest that RlPT and LbPT presumably play a key role in Pi acquisition by P. tabulaeformis via ectomycorrhizal fungi.

Via Jean-Michel Ané
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Functional characterization of the first filamentous fungal tRNA-isopentenyltransferase and its role in the virulence of Claviceps purpurea - Hinsch - 2016 - New Phytologist - Wiley Online Library

In plants, cytokinins (CKs) are synthesized de novo or by the degradation of modified tRNAs. Recently, the first fungal de novo pathway was identified within the plant pathogen Claviceps purpurea. As the deletion of the de novo pathway did not lead to a complete loss of CKs, this work focuses on the tRNA-modifying protein tRNA-isopentenyltransferase (CptRNA-IPT). The contribution of this enzyme to the CK pool of Claviceps and the role of CKs in the host–pathogen interaction are emphasized.
The effects of the deletion of cptRNA-ipt and the double deletion of cptRNA-ipt and the key gene of de novo biosynthesis cpipt-log on growth, CK biosynthesis and virulence were analyzed. In addition, the sites of action of CptRNA-IPT were visualized using reporter gene fusions.
In addition to CK-independent functions, CptRNA-IPT was essential for the biosynthesis of cis-zeatin (cZ) and contributed to the formation of isopentenyladenine (iP) and trans-zeatin (tZ). Although ΔcptRNA-ipt was reduced in virulence, the ‘CK-free’ double deletion mutant was nearly apathogenic.
The results prove a redundancy of the CK biosynthesis pathway in C. purpurea for iP and tZ formation. Moreover, we show, for the first time, that CKs are required for the successful establishment of a host–fungus interaction.
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A fungal endophyte helps plants to tolerate root herbivory through changes in gibberellin and jasmonate signaling

A fungal endophyte helps plants to tolerate root herbivory through changes in gibberellin and jasmonate signaling | MycorWeb Plant-Microbe Interactions | Scoop.it
Plant–microbe mutualisms can improve plant defense, but the impact of root endophytes on below-ground herbivore interactions remains unknown. We investigated the effects of the root endophyte Piriformospora indica on interactions between rice (Oryza sativa) plants and its root herbivore rice water weevil (RWW; Lissorhoptrus oryzophilus), and how plant jasmonic acid (JA) and GA regulate this tripartite interaction. Glasshouse experiments with wild-type rice and coi1-18 and Eui1-OX mutants combined with nutrient, jasmonate and gene expression analyses were used to test: whether RWW adult herbivory above ground influences subsequent damage caused by larval herbivory below ground; whether P. indica protects plants against RWW; and whether GA and JA signaling mediate these interactions. The endophyte induced plant tolerance to root herbivory. RWW adults and larvae acted synergistically via JA signaling to reduce root growth, while endophyte-elicited GA biosynthesis suppressed the herbivore-induced JA in roots and recovered plant growth. Our study shows for the first time the impact of a root endophyte on plant defense against below-ground herbivores, adds to growing evidence that induced tolerance may be an important root defense, and implicates GA as a signal component of inducible plant tolerance against biotic stress.

Via Stéphane Hacquard
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Cette forêt urbaine dont rêvent les Français

Cette forêt urbaine dont rêvent les Français | MycorWeb Plant-Microbe Interactions | Scoop.it
La ville idéale des Français ressemble à une forêt urbaine, selon un sondage mené par l’Ifop pour l’Union nationale des entreprises du paysage (Unep). L’Unep y voit un révélateur des attentes de l’opinion, plus ou moins satisfaites selon les villes.

Imaginez une ville-forêt où les constructions se fondent dans la luxuriance du végétal ! Telle est la ville idéale du futur, selon un sondage réalisé par l’Ifop pour l’Union nationale des entreprises du paysage (Unep). Rendue publique le 21 mars 2016, l’enquête a sondé un panel de 1 013 personnes, représentatif de la population française adulte. L’Unep y voit un révélateur des attentes de l’opinion, plus ou moins bien satisfaites sur le terrain.
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Ocean science: The rise of Rhizaria : Nature

Ocean science: The rise of Rhizaria : Nature | MycorWeb Plant-Microbe Interactions | Scoop.it
Large amoeba-like organisms known as Rhizaria have often been overlooked in studies of ocean biology and biogeochemistry. Underwater imaging and ecological network analyses are revealing their roles.

Do you know the name and evolutionary affiliation of any of the most conspicuous groups of single-celled organisms in the world's oceans? Did you guess the Rhizaria, or one of the more familiar groups of plankton that make up this supergroup, such as the Radiolaria, Acantharia or Foraminifera? If you didn't, you're not alone — until recently, neither did the vast majority of biological oceanographers. Biard et al.1 report online in Nature that the abundance and biomass of these enigmatic species in the ocean are much greater than previously recognized. In addition, Guidi et al.2 reveal the extent of the Rhizaria's involvement in the export of carbon from the atmosphere to the ocean depths.
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The Myth of Ethidium Bromide | In the Pipeline

The Myth of Ethidium Bromide | In the Pipeline | MycorWeb Plant-Microbe Interactions | Scoop.it
Ethidium bromide is found in pretty much every molecular biology lab around. Ask most biologists about handling it, and you’re get a fearful expression and advice to use gloves, etc. That’s because the compound is used to make DNA fluoresce when running gels, and it does that by slipping neatly between the base pairs (intercalation), like sliding a card into a deck. That is not something you want to have happen to your own DNA, naturally, so EthBr is widely believed to be a human mutagen that should be dealt with cautiously. Laboratory suppliers certainly think so: a search for “ethidium bromide alternative” will bring up a whole list of “non-toxic, non-mutagenic” substitutes on offer.
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