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Rescooped by Ryohei Thomas Nakano from Crosstalks in Plant-microbes interactions
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Arabidopsis thaliana root colonization by the nematophagous fungus Pochonia chlamydosporia is modulated by jasmonate signaling and leads to accelerated flowering and improved yield

Arabidopsis thaliana root colonization by the nematophagous fungus Pochonia chlamydosporia is modulated by jasmonate signaling and leads to accelerated flowering and improved yield | Interaction, and more... | Scoop.it
“ Pochonia chlamydosporia has been intensively studied in nematode control of different crops. We have investigated the interaction between P. chlamydosporia and the model system Arabidopsis thaliana under laboratory conditions in the absence of nematodes. This study demonstrates that P. chlamydosporia colonizes A. thaliana. Root colonization monitored with green fluorescent protein-tagged P. chlamydosporia and quantitative PCR (qPCR) quantitation methods revealed root cell invasion. Fungal inoculation reduced flowering time and stimulated plant growth, as determined by total FW increase, faster development of inflorescences and siliques, and a higher yield in terms of seed production per plant. Precocious flowering was associated with significant expression changes in key flowering-time genes. In addition, we also provided molecular and genetic evidence that point towards jasmonate signaling as an important factor to modulate progression of plant colonization by the fungus. Our results indicate that P. chlamydosporia provides benefits to the plant in addition to its nematophagous activity. This report highlights the potential of P. chlamydosporia to improve yield in economically important crops.”
Via Christophe Jacquet, Stéphane Hacquard, Francis Martin, Rey Thomas
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The pattern-recognition receptor CORE of Solanaceae detects bacterial cold-shock protein

The pattern-recognition receptor CORE of Solanaceae detects bacterial cold-shock protein | Interaction, and more... | Scoop.it
Plants and animals recognize microbial invaders by detecting microbe-associated molecular patterns (MAMPs) by cell surface receptors. Many plant species of the Solanaceae family detect the highly conserved nucleic acid binding motif RNP-1 of bacterial cold-shock proteins (CSPs), represented by the peptide csp22, as a MAMP. Here, we exploited the natural variation in csp22 perception observed between cultivated tomato (Solanum lycopersicum) and Solanum pennellii to map and identify the leucine-rich repeat (LRR) receptor kinase CORE (cold shock protein receptor) of tomato as the specific, high-affinity receptor site for csp22. Corroborating its function as a genuine receptor, heterologous expression of CORE in Arabidopsis thaliana conferred full sensitivity to csp22 and, importantly, it also rendered these plants more resistant to infection by the bacterial pathogen Pseudomonas syringae pv. tomato DC3000. Our study also confirms the biotechnological potential of enhancing plant immunity by interspecies transfer of highly effective pattern-recognition receptors such as CORE to different plant families.
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Indole-3-acetic acid production via the indole-3-pyruvate pathway by plant growth promoter Rhizobium tropici CIAT 899 is strongly inhibited by ammonium

Indole-3-acetic acid production via the indole-3-pyruvate pathway by plant growth promoter Rhizobium tropici CIAT 899 is strongly inhibited by ammonium | Interaction, and more... | Scoop.it
Like many rhizobia, Rhizobium tropici produces indole-3-acetic acid (IAA), an important signal molecule required for root hair infection in rhizobia-legume symbioses. However, the IAA biosynthesis pathway and its regulation by R. tropici are still poorly understood. In this study, IAA synthesis and the effects of mineral N in IAA production by R. tropici   CIAT 899 were verified by ultraperformance liquid chromatography-mass spectrometry (UPLC-MS). Furthermore, expression of genes related to IAA biosynthesis and metabolism were evaluated by RT-qPCR. Results indicated that IAA production by CIAT 899 was 12 times lower in the presence of NH4+
. Moreover, it was found that indole-3-pyruvate (IPyA) is the major IAA biosynthesis intermediate. Genes y4wE, lao and iorA were identified by analysis of R. tropici   genome in silico and were upregulated by tryptophan, indicating a possible role of these genes in IAA biosynthesis by CIAT 899. In conclusion, we show that IPyA is the major pathway for IAA biosynthesis in CIAT 899 and that its production is strongly inhibited by NH4+
. Although present results arose from in vitro experiments, they provide new insight into the role of nitrogen in early events related to legume nodulation.
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Characterization of a dynamic metabolon producing the defense compound dhurrin in sorghum

Characterization of a dynamic metabolon producing the defense compound dhurrin in sorghum | Interaction, and more... | Scoop.it
Metabolic highways may be orchestrated by the assembly of sequential enzymes into protein complexes, or metabolons, to facilitate efficient channeling of intermediates and to prevent undesired metabolic cross-talk while maintaining metabolic flexibility. Here we report the isolation of the dynamic metabolon that catalyzes the formation of the cyanogenic glucoside dhurrin, a defense compound produced in sorghum plants. The metabolon was reconstituted in liposomes, which demonstrated the importance of membrane surface charge and the presence of the glucosyltransferase for metabolic channeling. We used in planta fluorescence lifetime imaging microscopy and fluorescence correlation spectroscopy to study functional and structural characteristics of the metabolon. Understanding the regulation of biosynthetic metabolons offers opportunities to optimize synthetic biology approaches for efficient production of high-value products in heterologous hosts.
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pKAMA-ITACHI vectors for highly efficient CRISPR/Cas9-mediated gene knockout in Arabidopsis thaliana

pKAMA-ITACHI vectors for highly efficient CRISPR/Cas9-mediated gene knockout in Arabidopsis thaliana | Interaction, and more... | Scoop.it
The CRISPR/Cas9 system is widely used as a tool for genome engineering in various organisms. A complex consisting of Cas9 and single guide RNA (sgRNA) induces a DNA double-strand break in a sequence-specific manner, resulting in knockout. Some binary vectors for CRISPR/Cas9 in plants have been reported, but there is a problem with low efficiency. Here, we present a newly developed, highly efficient CRISPR/Cas9 vector for Arabidopsis thaliana, pKAMA-ITACHI Red (pKIR), harboring the RIBOSOMAL PROTEIN S5 A (RPS5A) promoter to drive Cas9. The RPS5A promoter maintains high constitutive expression at all developmental stages starting from the egg cell and including meristematic cells. Even in the T1 generation, pKIR induced null phenotypes in some genes: PHYTOENE DESATURASE 3 (PDS3), AGAMOUS (AG), and DUO POLLEN 1 (DUO1). Mutations induced by pKIR were carried in the germ cell line of the T1 generation. Surprisingly, in some lines, 100% of the T2 plants had the adh1 (ALCOHOL DEHYDROGENASE 1) null phenotype, indicating that pKIR strongly induced heritable mutations. Cas9-free T2 mutant plants were obtained by removing T2 seeds expressing a fluorescent marker in pKIR. Our results suggest that the pKIR system is a powerful molecular tool for genome engineering in Arabidopsis.
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Genome-wide screen identifies host colonization determinants in a bacterial gut symbiont

Genome-wide screen identifies host colonization determinants in a bacterial gut symbiont | Interaction, and more... | Scoop.it
Animal guts are often colonized by host-specialized bacterial species to the exclusion of other transient microorganisms, but the genetic basis of colonization ability is largely unknown. The bacterium Snodgrassella alvi is a dominant gut symbiont in honey bees, specialized in colonizing the hindgut epithelium. We developed methods for transposon-based mutagenesis in S. alvi and, using high-throughput DNA sequencing, screened genome-wide transposon insertion (Tn-seq) and transcriptome (RNA-seq) libraries to characterize both the essential genome and the genes facilitating host colonization. Comparison of Tn-seq results from laboratory cultures and from monoinoculated worker bees reveal that 519 of 2,226 protein-coding genes in S. alvi are essential in culture, whereas 399 are not essential but are beneficial for gut colonization. Genes facilitating colonization fall into three broad functional categories: extracellular interactions, metabolism, and stress responses. Extracellular components with strong fitness benefits in vivo include trimeric autotransporter adhesins, O antigens, and type IV pili (T4P). Experiments with T4P mutants establish that T4P in S. alvi likely function in attachment and biofilm formation, with knockouts experiencing a competitive disadvantage in vivo. Metabolic processes promoting colonization include essential amino acid biosynthesis and iron acquisition pathways, implying nutrient scarcity within the hindgut environment. Mechanisms to deal with various stressors, such as for the repair of double-stranded DNA breaks and protein quality control, are also critical in vivo. This genome-wide study identifies numerous genetic networks underlying colonization by a gut commensal in its native host environment, including some known from more targeted studies in other host–microbe symbioses.
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The pangenome of an agronomically important crop plant Brassica oleracea

The pangenome of an agronomically important crop plant Brassica oleracea | Interaction, and more... | Scoop.it
There is an increasing awareness that as a result of structural variation, a reference sequence representing a genome of a single individual is unable to capture all of the gene repertoire found in the species. A large number of genes affected by presence/absence and copy number variation suggest that it may contribute to phenotypic and agronomic trait diversity. Here we show by analysis of the Brassica oleracea pangenome that nearly 20% of genes are affected by presence/absence variation. Several genes displaying presence/absence variation are annotated with functions related to major agronomic traits, including disease resistance, flowering time, glucosinolate metabolism and vitamin biosynthesis.
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Transient RNA-DNA Hybrids Are Required for Efficient Double-Strand Break Repair

Transient RNA-DNA Hybrids Are Required for Efficient Double-Strand Break Repair | Interaction, and more... | Scoop.it
Highlights
•Deletion or overexpression of RNase H inhibits HR-mediated DSB repair in S. pombe
•RNA polymerase II and RNA-DNA hybrids are enriched around DSB sites
•Stabilization of RNA-DNA hybrids impairs RPA recruitment to ssDNA overhangs
•RNA-DNA hybrids are essential for maintaining repetitive DNA regions around DSBs
Summary
RNA-DNA hybrids are a major internal cause of DNA damage within cells, and their degradation by RNase H enzymes is important for maintaining genomic stability. Here, we identified an unexpected role for RNA-DNA hybrids and RNase H enzymes in DNA repair. Using a site-specific DNA double-strand break (DSB) system in Schizosaccharomyces pombe, we showed that RNA-DNA hybrids form as part of the homologous-recombination (HR)-mediated DSB repair process and that RNase H enzymes are essential for their degradation and efficient completion of DNA repair. Deleting RNase H stabilizes RNA-DNA hybrids around DSB sites and strongly impairs recruitment of the ssDNA-binding RPA complex. In contrast, overexpressing RNase H1 destabilizes these hybrids, leading to excessive strand resection and RPA recruitment and to severe loss of repeat regions around DSBs. Our study challenges the existing model of HR-mediated DSB repair and reveals a surprising role for RNA-DNA hybrids in maintaining genomic stability.
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Allelic barley MLA immune receptors recognize sequence-unrelated avirulence effectors of the powdery mildew pathogen

Allelic barley MLA immune receptors recognize sequence-unrelated avirulence effectors of the powdery mildew pathogen | Interaction, and more... | Scoop.it
Disease-resistance genes encoding intracellular nucleotide-binding domain and leucine-rich repeat proteins (NLRs) are key components of the plant innate immune system and typically detect the presence of isolate-specific avirulence (AVR) effectors from pathogens. NLR genes define the fastest-evolving gene family of flowering plants and are often arranged in gene clusters containing multiple paralogs, contributing to copy number and allele-specific NLR variation within a host species. Barley mildew resistance locus a (Mla) has been subject to extensive functional diversification, resulting in allelic resistance specificities each recognizing a cognate, but largely unidentified, AVRa gene of the powdery mildew fungus, Blumeria graminis f. sp. hordei (Bgh). We applied a transcriptome-wide association study among 17 Bgh isolates containing different AVRa genes and identified AVRa1 and AVRa13, encoding candidate-secreted effectors recognized by Mla1 and Mla13 alleles, respectively. Transient expression of the effector genes in barley leaves or protoplasts was sufficient to trigger Mla1 or Mla13 allele-specific cell death, a hallmark of NLR receptor-mediated immunity. AVRa1 and AVRa13 are phylogenetically unrelated, demonstrating that certain allelic MLA receptors evolved to recognize sequence-unrelated effectors. They are ancient effectors because corresponding loci are present in wheat powdery mildew. AVRA1 recognition by barley MLA1 is retained in transgenic Arabidopsis, indicating that AVRA1 directly binds MLA1 or that its recognition involves an evolutionarily conserved host target of AVRA1. Furthermore, analysis of transcriptome-wide sequence variation among the Bgh isolates provides evidence for Bgh population structure that is partially linked to geographic isolation.
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Assembly and transfer of tripartite integrative and conjugative genetic elements

Assembly and transfer of tripartite integrative and conjugative genetic elements | Interaction, and more... | Scoop.it
Integrative and conjugative elements (ICEs) are ubiquitous mobile genetic elements present as “genomic islands” within bacterial chromosomes. Symbiosis islands are ICEs that convert nonsymbiotic mesorhizobia into symbionts of legumes. Here we report the discovery of symbiosis ICEs that exist as three separate chromosomal regions when integrated in their hosts, but through recombination assemble as a single circular ICE for conjugative transfer. Whole-genome comparisons revealed exconjugants derived from nonsymbiotic mesorhizobia received three separate chromosomal regions from the donor Mesorhizobium ciceri WSM1271. The three regions were each bordered by two nonhomologous integrase attachment (att) sites, which together comprised three homologous pairs of attL and attR sites. Sequential recombination between each attL and attR pair produced corresponding attP and attB sites and joined the three fragments to produce a single circular ICE, ICEMcSym1271. A plasmid carrying the three attP sites was used to recreate the process of tripartite ICE integration and to confirm the role of integrase genes intS, intM, and intG in this process. Nine additional tripartite ICEs were identified in diverse mesorhizobia and transfer was demonstrated for three of them. The transfer of tripartite ICEs to nonsymbiotic mesorhizobia explains the evolution of competitive but suboptimal N2-fixing strains found in Western Australian soils. The unheralded existence of tripartite ICEs raises the possibility that multipartite elements reside in other organisms, but have been overlooked because of their unusual biology. These discoveries reveal mechanisms by which integrases dramatically manipulate bacterial genomes to allow cotransfer of disparate chromosomal regions.
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Using a Control to Better Understand Phyllosphere Microbiota

Using a Control to Better Understand Phyllosphere Microbiota | Interaction, and more... | Scoop.it
An important data gap in our understanding of the phyllosphere surrounds the origin of the many microbes described as phyllosphere communities. Most sampling in phyllosphere research has focused on the collection of microbiota without the use of a control, so the opportunity to determine which taxa are actually driven by the biology and physiology of plants as opposed to introduced by environmental forces has yet to be fully realized. To address this data gap, we used plastic plants as inanimate controls adjacent to live tomato plants (phyllosphere) in the field with the hope of distinguishing between bacterial microbiota that may be endemic to plants as opposed to introduced by environmental forces. Using 16S rRNA gene amplicons to study bacterial membership at four time points, we found that the vast majority of all species-level operational taxonomic units were shared at all time-points. Very few taxa were unique to phyllosphere samples. A higher taxonomic diversity was consistently observed in the control samples. The high level of shared taxonomy suggests that environmental forces likely play a very important role in the introduction of microbes to plant surfaces. The observation that very few taxa were unique to the plants compared to the number that were unique to controls was surprising and further suggests that a subset of environmentally introduced taxa thrive on plants. This finding has important implications for improving our approach to the description of core phytobiomes as well as potentially helping us better understand how foodborne pathogens may become associated with plant surfaces.

Via Matt Agler, Stéphane Hacquard
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The Arabidopsis CERK1‐associated kinase PBL27 connects chitin perception to MAPK activation

The Arabidopsis CERK1‐associated kinase PBL27 connects chitin perception to MAPK activation | Interaction, and more... | Scoop.it
Perception of microbe‐associated molecular patterns by host cell surface pattern recognition receptors (PRRs) triggers the intracellular activation of mitogen‐activated protein kinase (MAPK) cascades. However, it is not known how PRRs transmit immune signals to MAPK cascades in plants. Here, we identify a complete phospho‐signaling transduction pathway from PRR‐mediated pathogen recognition to MAPK activation in plants. We found that the receptor‐like cytoplasmic kinase PBL27 connects the chitin receptor complex CERK1‐LYK5 and a MAPK cascade. PBL27 interacts with both CERK1 and the MAPK kinase kinase MAPKKK5 at the plasma membrane. Knockout mutants of MAPKKK5 compromise chitin‐induced MAPK activation and disease resistance to Alternaria brassicicola. PBL27 phosphorylates MAPKKK5 in vitro, which is enhanced by phosphorylation of PBL27 by CERK1. The chitin perception induces disassociation between PBL27 and MAPKKK5 in vivo. Furthermore, genetic evidence suggests that phosphorylation of MAPKKK5 by PBL27 is essential for chitin‐induced MAPK activation in plants. These data indicate that PBL27 is the MAPKKK kinase that provides the missing link between the cell surface chitin receptor and the intracellular MAPK cascade in plants.
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The ISME Journal - Ubiquitous marine bacterium inhibits diatom cell division

The ISME Journal - Ubiquitous marine bacterium inhibits diatom cell division | Interaction, and more... | Scoop.it
Intricate relationships between microorganisms structure the exchange of molecules between taxa, driving their physiology and evolution. On a global scale, this molecular trade is an integral component of biogeochemical cycling. As important microorganisms in the world’s oceans, diatoms and bacteria have a large impact on marine biogeochemistry. Here, we describe antagonistic effects of the globally distributed flavobacterium Croceibacter atlanticus on a phylogenetically diverse group of diatoms. We used the model diatom Thalassiosira pseudonana to study the antagonistic impact in more detail. In co-culture, C. atlanticus attaches to T. pseudonana and inhibits cell division, inducing diatom cells to become larger and increase in chlorophyll a fluorescence. These changes could be explained by an absence of cytokinesis that causes individual T. pseudonana cells to elongate, accumulate more plastids and become polyploid. These morphological changes could benefit C. atlanticus by augmenting the colonizable surface area of the diatom, its photosynthetic capabilities and possibly its metabolic secretions.
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Evolution, genomics and epidemiology of Pseudomonas syringae

Evolution, genomics and epidemiology of Pseudomonas syringae | Interaction, and more... | Scoop.it
A remarkable shift in our understanding of plant-pathogenic bacteria is underway. Until recently, nearly all research on phytopathogenic bacteria was focused on a small number of model strains, which provided a deep, but narrow, perspective on plant–microbe interactions. Advances in genome sequencing technologies have changed this by enabling the incorporation of much greater diversity into comparative and functional research. We are now moving beyond a typological understanding of a select collection of strains to a more generalized appreciation of the breadth and scope of plant–microbe interactions. The study of natural populations and evolution has particularly benefited from the expansion of genomic data. We are beginning to have a much deeper understanding of the natural genetic diversity, niche breadth, ecological constraints and defining characteristics of phytopathogenic species. Given this expanding genomic and ecological knowledge, we believe the time is ripe to evaluate what we know about the evolutionary dynamics of plant pathogens.
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Intracellular innate immune surveillance devices in plants and animals

Intracellular innate immune surveillance devices in plants and animals | Interaction, and more... | Scoop.it
Multicellular eukaryotes coevolve with microbial pathogens, which exert strong selective pressure on the immune systems of their hosts. Plants and animals use intracellular proteins of the nucleotide-binding domain, leucine-rich repeat (NLR) superfamily to detect many types of microbial pathogens. The NLR domain architecture likely evolved independently and convergently in each kingdom, and the molecular mechanisms of pathogen detection by plant and animal NLRs have long been considered to be distinct. However, microbial recognition mechanisms overlap, and it is now possible to discern important key trans-kingdom principles of NLR-dependent immune function. Here, we attempt to articulate these principles. We propose that the NLR architecture has evolved for pathogen-sensing in diverse organisms because of its utility as a tightly folded “hair trigger” device into which a virtually limitless number of microbial detection platforms can be integrated. Recent findings suggest means to rationally design novel recognition capabilities to counter disease.
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Root isoflavonoids and hairy root transformation influence key bacterial taxa in the soybean rhizosphere

Root isoflavonoids and hairy root transformation influence key bacterial taxa in the soybean rhizosphere | Interaction, and more... | Scoop.it
Rhizodeposits play a key role in shaping rhizosphere microbial communities. In soybean, isoflavonoids are a key rhizodeposit component that aid in plant defense and enable symbiotic associations with rhizobia. However, it is uncertain if and how they influence rhizosphere microbial communities. Isoflavonoid biosynthesis was silenced via RNA interference of isoflavone synthase in soybean hairy root composite plants. Rhizosphere soil fractions tightly associated with roots were isolated, and PCR amplicons from 16S rRNA gene variable regions V1-V3 and V3-V5 from these fractions were sequenced using 454. The resulting data was resolved using MOTHUR and vegan to identify bacterial taxa and evaluate changes in rhizosphere bacterial communities. The soybean rhizosphere was enriched in Proteobacteria and Bacteroidetes, and had relatively lower levels of Actinobacteria and Acidobacteria compared to bulk soil. Isoflavonoids had a small effect on bacterial community structure, and in particular on the abundance of Xanthomonads and Comamonads. The effect of hairy root transformation on rhizosphere bacterial communities was largely similar to untransformed plant roots with ∼74% of the bacterial families displaying similar colonization underscoring the suitability of this technique to evaluate the influence of plant roots on rhizosphere bacterial communities. However, hairy root transformation had notable influence on Sphingomonads and Acidobacteria. This article is protected by copyright. All rights reserved.
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Volatile compounds emitted by diverse phytopathogenic microorganisms promote plant growth and flowering through cytokinin action

Volatile compounds emitted by diverse phytopathogenic microorganisms promote plant growth and flowering through cytokinin action | Interaction, and more... | Scoop.it
It is known that volatile emissions from some beneficial rhizosphere microorganisms promote plant growth. Here we show that volatile compounds (VCs) emitted by phylogenetically diverse rhizosphere and non-rhizhosphere bacteria and fungi (including plant pathogens and microbes that do not normally interact mutualistically with plants) promote growth and flowering of various plant species, including crops. In Arabidopsis plants exposed to VCs emitted by the phytopathogen Alternaria alternata, changes included enhancement of photosynthesis and accumulation of high levels of cytokinins (CKs) and sugars. Evidence obtained using transgenic Arabidopsis plants with altered CK status show that CKs play essential roles in this phenomenon, because growth and flowering responses to the VCs were reduced in mutants with CK-deficiency (35S:AtCKX1) or low receptor sensitivity (ahk2/3). Further, we demonstrate that the plant responses to fungal VCs are light-dependent. Transcriptomic analyses of Arabidopsis leaves exposed to A. alternata VCs revealed changes in the expression of light- and CK-responsive genes involved in photosynthesis, growth and flowering. Notably, many genes differentially expressed in plants treated with fungal VCs were also differentially expressed in plants exposed to VCs emitted by the plant growth promoting rhizobacterium Bacillus subtilis GB03, suggesting that plants react to microbial VCs through highly conserved regulatory mechanisms.
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Microbe-mediated host defence drives the evolution of reduced pathogen virulence

Microbe-mediated host defence drives the evolution of reduced pathogen virulence | Interaction, and more... | Scoop.it
Microbes that protect their hosts from pathogens are widespread in nature and are attractive disease control agents. Given that pathogen adaptation to barriers against infection can drive changes in pathogen virulence, ‘defensive microbes’ may shape disease severity. Here we show that co-evolving a microbe with host-protective properties (Enterococcus faecalis) and a pathogen (Staphylococcus aureus) within Caenorhabditis elegans hosts drives the evolution of reduced pathogen virulence as a by-product of adaptation to the defensive microbe. Using both genomic and phenotypic analyses, we discover that the production of fewer iron-scavenging siderophores by the pathogen reduces the fitness of the defensive microbe and underpins the decline in pathogen virulence. These data show that defensive microbes can shape the evolution of pathogen virulence and that the mechanism of pathogen resistance can determine the direction of virulence evolution.
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Arabidopsis thaliana GH3.5 acyl acid amido synthetase mediates metabolic crosstalk in auxin and salicylic acid homeostasis

Arabidopsis thaliana GH3.5 acyl acid amido synthetase mediates metabolic crosstalk in auxin and salicylic acid homeostasis | Interaction, and more... | Scoop.it
In Arabidopsis thaliana, the acyl acid amido synthetase Gretchen Hagen 3.5 (AtGH3.5) conjugates both indole-3-acetic acid (IAA) and salicylic acid (SA) to modulate auxin and pathogen response pathways. To understand the molecular basis for the activity of AtGH3.5, we determined the X-ray crystal structure of the enzyme in complex with IAA and AMP. Biochemical analysis demonstrates that the substrate preference of AtGH3.5 is wider than originally described and includes the natural auxin phenylacetic acid (PAA) and the potential SA precursor benzoic acid (BA). Residues that determine IAA versus BA substrate preference were identified. The dual functionality of AtGH3.5 is unique to this enzyme although multiple IAA-conjugating GH3 proteins share nearly identical acyl acid binding sites. In planta analysis of IAA, PAA, SA, and BA and their respective aspartyl conjugates were determined in wild-type and overexpressing lines of A. thaliana. This study suggests that AtGH3.5 conjugates auxins (i.e., IAA and PAA) and benzoates (i.e., SA and BA) to mediate crosstalk between different metabolic pathways, broadening the potential roles for GH3 acyl acid amido synthetases in plants.
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A selective insecticidal protein from Pseudomonas for controlling corn rootworms

A selective insecticidal protein from Pseudomonas for controlling corn rootworms | Interaction, and more... | Scoop.it
Soil microbes yield insecticidal peptide

The microbial peptide BT, derived from the bacterium Bacillus thuringiensis, is widely used to protect crops from insect pests. Schellenberger et al. identified another insecticidal peptide from a different soil-dwelling bacterium, Pseudomonas chlororaphis (see the Perspective by Tabashnik). Corn plants expressing the Pseudomonas peptide were protected from attack by western corn rootworm. Rootworms that were resistant to BT were susceptible to the Pseudomonas peptide. Addition of another insecticidal peptide diversifies the arsenal against insect pests, which may slow down the development of resistance.

Science, this issue p. 634; see also p. 552
Abstract

The coleopteran insect western corn rootworm (WCR) (Diabrotica virgifera virgifera LeConte) is a devastating crop pest in North America and Europe. Although crop plants that produce Bacillus thuringiensis (Bt) proteins can limit insect infestation, some insect populations have evolved resistance to Bt proteins. Here we describe an insecticidal protein, designated IPD072Aa, that is isolated from Pseudomonas chlororaphis. Transgenic corn plants expressing IPD072Aa show protection from WCR insect injury under field conditions. IPD072Aa leaves several lepidopteran and hemipteran insect species unaffected but is effective in killing WCR larvae that are resistant to Bt proteins produced by currently available transgenic corn. IPD072Aa can be used to protect corn crops against WCRs.
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The fungal-specific β-glucan-binding lectin FGB1 alters cell-wall composition and suppresses glucan-triggered immunity in plants

The fungal-specific β-glucan-binding lectin FGB1 alters cell-wall composition and suppresses glucan-triggered immunity in plants | Interaction, and more... | Scoop.it
β-glucans are well-known modulators of the immune system in mammals but little is known about β-glucan triggered immunity in planta. Here we show by isothermal titration calorimetry, circular dichroism spectroscopy and nuclear magnetic resonance spectroscopy that the FGB1 gene from the root endophyte Piriformospora indica encodes for a secreted fungal-specific β-glucan-binding lectin with dual function. This lectin has the potential to both alter fungal cell wall composition and properties, and to efficiently suppress β-glucan-triggered immunity in different plant hosts, such as Arabidopsis, barley and Nicotiana benthamiana. Our results hint at the existence of fungal effectors that deregulate innate sensing of β-glucan in plants.
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Sulfur deficiency–induced repressor proteins optimize glucosinolate biosynthesis in plants

Sulfur deficiency–induced repressor proteins optimize glucosinolate biosynthesis in plants | Interaction, and more... | Scoop.it
Glucosinolates (GSLs) in the plant order of the Brassicales are sulfur-rich secondary metabolites that harbor antipathogenic and antiherbivory plant-protective functions and have medicinal properties, such as carcinopreventive and antibiotic activities. Plants repress GSL biosynthesis upon sulfur deficiency (−S); hence, field performance and medicinal quality are impaired by inadequate sulfate supply. The molecular mechanism that links –S to GSL biosynthesis has remained understudied. We report here the identification of the –S marker genes sulfur deficiency induced 1 (SDI1) and SDI2 acting as major repressors controlling GSL biosynthesis in Arabidopsis under –S condition. SDI1 and SDI2 expression negatively correlated with GSL biosynthesis in both transcript and metabolite levels. Principal components analysis of transcriptome data indicated that SDI1 regulates aliphatic GSL biosynthesis as part of –S response. SDI1 was localized to the nucleus and interacted with MYB28, a major transcription factor that promotes aliphatic GSL biosynthesis, in both yeast and plant cells. SDI1 inhibited the transcription of aliphatic GSL biosynthetic genes by maintaining the DNA binding composition in the form of an SDI1-MYB28 complex, leading to down-regulation of GSL biosynthesis and prioritization of sulfate usage for primary metabolites under sulfur-deprived conditions.
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Aboveground and Belowground Herbivores Synergistically Induce Volatile Organic Sulfur Compound Emissions from Shoots but Not from Roots

Aboveground and Belowground Herbivores Synergistically Induce Volatile Organic Sulfur Compound Emissions from Shoots but Not from Roots | Interaction, and more... | Scoop.it
Studies on aboveground (AG) plant organs have shown that volatile organic compound (VOC) emissions differ between simultaneous attack by herbivores and single herbivore attack. There is growing evidence that interactive effects of simultaneous herbivory also occur across the root-shoot interface. In our study, Brassica rapa roots were infested with root fly larvae (Delia radicum) and the shoots infested with Pieris brassicae, either singly or simultaneously, to study these root-shoot interactions. As an analytical platform, we used Proton Transfer Reaction Mass Spectrometry (PTR-MS) to investigate VOCs over a 3 day time period. Our set-up allowed us to monitor root and shoot emissions concurrently on the same plant. Focus was placed on the sulfur-containing compounds; methanethiol, dimethylsulfide (DMS), and dimethyldisulfide (DMDS), because these compounds previously have been shown to be biologically active in the interactions of Brassica plants, herbivores, parasitoids, and predators, yet have received relatively little attention. The shoots of plants simultaneously infested with AG and belowground (BG) herbivores emitted higher levels of sulfur-containing compounds than plants with a single herbivore species present. In contrast, the emission of sulfur VOCs from the plant roots increased as a consequence of root herbivory, independent of the presence of an AG herbivore. The onset of root emissions was more rapid after damage than the onset of shoot emissions. The shoots of double infested plants also emitted higher levels of methanol. Thus, interactive effects of root and shoot herbivores exhibit more strongly in the VOC emissions from the shoots than from the roots, implying the involvement of specific signaling interactions.
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Scooped by Ryohei Thomas Nakano
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Root Development and Endosymbioses: DELLAs Lead the Orchestra

Root Development and Endosymbioses: DELLAs Lead the Orchestra | Interaction, and more... | Scoop.it
DELLA proteins, acting as integrators of gibberellin (GA) action, are emerging as key regulators of root system architecture. Recent studies have revealed how they dictate the dynamics of root growth and are required for the establishment of root endosymbioses with rhizobial bacteria and mycorrhizal fungi. Like conductors, DELLAs can thereby harmonize root development depending on soil environments.
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Rescooped by Ryohei Thomas Nakano from Host-Microbe Interactions. Plant Biology.
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The Plant Microbiota: Systems-Level Insights and Perspectives - Annual Review of Genetics

The Plant Microbiota: Systems-Level Insights and Perspectives - Annual Review of Genetics | Interaction, and more... | Scoop.it

Via Tatsuya Nobori
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