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New Phytologist: The dispensable chromosome of Leptosphaeria maculans shelters an effector gene conferring avirulence towards Brassica rapa (2013)

New Phytologist: The dispensable chromosome of Leptosphaeria maculans shelters an effector gene conferring avirulence towards Brassica rapa (2013) | Plant-Microbe Interaction | Scoop.it

Phytopathogenic fungi frequently contain dispensable chromosomes, some of which contribute to host range or pathogenicity. In Leptosphaeria maculans, the stem canker agent of oilseed rape (Brassica napus), the minichromosome was previously suggested to be dispensable, without evidence for any role in pathogenicity.

Using genetic and genomic approaches, we investigated the inheritance and molecular determinant of an L. maculans–Brassica rapa incompatible interaction.

Single gene control of the resistance was found, while all markers located on the L. maculans minichromosome, absent in the virulent parental isolate, co-segregated with the avirulent phenotype. Only one candidate avirulence gene was identified on the minichromosome, validated by complementation experiments and termed AvrLm11. The minichromosome was frequently lost following meiosis, but the frequency of isolates lacking it remained stable in field populations sampled at a 10-yr time interval, despite a yearly sexual stage in the L. maculans life cycle.

This work led to the cloning of a new ‘lost in the middle of nowhere’ avirulence gene of L. maculans, interacting with a B. rapa resistance gene termed Rlm11 and introgressed into B. napus. It demonstrated the dispensability of the L. maculans minichromosome and suggested that its loss generates a fitness deficit.


Via Kamoun Lab @ TSL
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Rescooped by Guogen Yang from Plant Immunity And Microbial Effectors
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The maize disease resistance gene Htn1 against northern corn leaf blight encodes a wall-associated receptor-like kinase

Northern corn leaf blight (NCLB) is one of the most devastating fungal diseases of maize. The Htn1 disease resistance gene confers quantitative field resistance against most NCLB isolates. Here we show that Htn1 encodes a putative wall-associated receptor-like kinase (RLK). RLKs act as important components of the first tier of the plant innate immune system by perceiving pathogen- or host-derived elicitors on the cell surface. RLKs are often associated with resistance to nonadapted pathogens and are a component of nonhost resistance. Our work demonstrates that the Htn1-RLK plays an important role in host resistance against adapted fungal pathogens.


Via IPM Lab
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Genome-wide Identification and Expression Analysis of the CDPK Gene Family in Grape, Vitis spp

Genome-wide Identification and Expression Analysis of the CDPK Gene Family in Grape, Vitis spp | Plant-Microbe Interaction | Scoop.it

Background

Calcium-dependent protein kinases (CDPKs) play vital roles in plant growth and development, biotic and abiotic stress responses, and hormone signaling. Little is known about the CDPK gene family in grapevine.

Results

In this study, we performed a genome-wide analysis of the 12X grape genome (Vitis vinifera) and identified nineteen CDPK genes. Comparison of the structures of grape CDPK genes allowed us to examine their functional conservation and differentiation. Segmentally duplicated grape CDPK genes showed high structural conservation and contributed to gene family expansion. Additional comparisons between grape and Arabidopsis thaliana demonstrated that several grape CDPK genes occured in the corresponding syntenic blocks of Arabidopsis, suggesting that these genes arose before the divergence of grapevine and Arabidopsis. Phylogenetic analysis divided the grape CDPK genes into four groups. Furthermore, we examined the expression of the corresponding nineteen homologous CDPK genes in the Chinese wild grape (Vitis pseudoreticulata) under various conditions, including biotic stress, abiotic stress, and hormone treatments. The expression profiles derived from reverse transcription and quantitative PCR suggested that a large number of VpCDPKs responded to various stimuli on the transcriptional level, indicating their versatile roles in the responses to biotic and abiotic stresses. Moreover, we examined the subcellular localization of VpCDPKs by transiently expressing six VpCDPK-GFP fusion proteins in Arabidopsis mesophyll protoplasts; this revealed high variability consistent with potential functional differences.

Conclusions

Taken as a whole, our data provide significant insights into the evolution and function of grape CDPKs and a framework for future investigation of grape CDPK genes.


Via Christophe Jacquet
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Rescooped by Guogen Yang from Plants and Microbes
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Developmental Cell: Chloroplast Stromules Function during Innate Immunity (2015)

Developmental Cell: Chloroplast Stromules Function during Innate Immunity (2015) | Plant-Microbe Interaction | Scoop.it
Chloroplast stromules are induced during plant immune responsesPro-PCD signals such as SA and H2O2 induce stromulesStromules form dynamic connections with nucleus during immune responsesConstitutively induced stromules enhance PCD during plant immune responses


Inter-organellar communication is vital for successful innate immune responses that confer defense against pathogens. However, little is known about how chloroplasts, which are a major production site of pro-defense molecules, communicate and coordinate with other organelles during defense. Here we show that chloroplasts send out dynamic tubular extensions called stromules during innate immunity or exogenous application of the pro-defense signals, hydrogen peroxide (H2O2) and salicylic acid. Interestingly, numerous stromules surround nuclei during defense response, and these connections correlate with an accumulation of chloroplast-localized NRIP1 defense protein and H2O2 in the nucleus. Furthermore, silencing and knockout of chloroplast unusual positioning 1 (CHUP1) that encodes a chloroplast outer envelope protein constitutively induces stromules in the absence of pathogen infection and enhances programmed cell death. These results support a model in which stromules aid in the amplification and/or transport of pro-defense signals into the nucleus and other subcellular compartments during immunity.


Via Kamoun Lab @ TSL
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Rescooped by Guogen Yang from Plants and Microbes
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Plant Phys Cover: The WRKY45-Dependent Signaling Pathway Is Required For Resistance against Striga hermonthica Parasitism (2015)

Plant Phys Cover: The WRKY45-Dependent Signaling Pathway Is Required For Resistance against Striga hermonthica Parasitism (2015) | Plant-Microbe Interaction | Scoop.it

The root hemiparasite witchweed (Striga spp.) is a devastating agricultural pest that causes losses of up to $1 billion US annually in sub-Saharan Africa. Development of resistant crops is one of the cost-effective ways to address this problem. However, the molecular mechanisms underlying resistance are not well understood. To understand molecular events upon Striga spp. infection, we conducted genome-scale RNA sequencing expression analysis using Striga hermonthica-infected rice (Oryza sativa) roots. We found that transcripts grouped under the Gene Ontology term defense response were significantly enriched in up-regulated differentially expressed genes. In particular, we found that both jasmonic acid (JA) and salicylic acid (SA) pathways were induced, but the induction of the JA pathway preceded that of the SA pathway. Foliar application of JA resulted in higher resistance. The hebiba mutant plants, which lack the JA biosynthesis gene ALLENE OXIDE CYCLASE, exhibited severe S. hermonthica susceptibility. The resistant phenotype was recovered by application of JA. By contrast, the SA-deficient NahG rice plants were resistant against S. hermonthica, indicating that endogenous SA is not required for resistance. However, knocking down WRKY45, a regulator of the SA/benzothiadiazole pathway, resulted in enhanced susceptibility. Interestingly, NahG plants induced the JA pathway, which was down-regulated in WRKY45-knockdown plants, linking the resistant and susceptible phenotypes to the JA pathway. Consistently, the susceptibility phenotype in the WRKY45-knockdown plants was recovered by foliar JA application. These results point to a model in which WRKY45 modulates a cross talk in resistance against S. hermonthica by positively regulating both SA/benzothiadiazole and JA pathways.


Via Kamoun Lab @ TSL
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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The bHLH transcription factor BIS1 controls the iridoid branch of the monoterpenoid indole alkaloid pathway in Catharanthus roseus

The bHLH transcription factor BIS1 controls the iridoid branch of the monoterpenoid indole alkaloid pathway in Catharanthus roseus | Plant-Microbe Interaction | Scoop.it

Abstract

Plants make specialized bioactive metabolites to defend themselves against attackers. The conserved control mechanisms are based on transcriptional activation of the respective plant species-specific biosynthetic pathways by the phytohormone jasmonate. Knowledge of the transcription factors involved, particularly in terpenoid biosynthesis, remains fragmentary. By transcriptome analysis and functional screens in the medicinal plant Catharanthus roseus (Madagascar periwinkle), the unique source of the monoterpenoid indole alkaloid (MIA)-type anticancer drugs vincristine and vinblastine, we identified a jasmonate-regulated basic helix–loop–helix (bHLH) transcription factor from clade IVa inducing the monoterpenoid branch of the MIA pathway. The bHLH iridoid synthesis 1 (BIS1) transcription factor transactivated the expression of all of the genes encoding the enzymes that catalyze the sequential conversion of the ubiquitous terpenoid precursor geranyl diphosphate to the iridoid loganic acid. BIS1 acted in a complementary manner to the previously characterized ethylene response factor Octadecanoid derivative-Responsive Catharanthus APETALA2-domain 3 (ORCA3) that transactivates the expression of several genes encoding the enzymes catalyzing the conversion of loganic acid to the downstream MIAs. In contrast to ORCA3, overexpression of BIS1 was sufficient to boost production of high-value iridoids and MIAs in C. roseus suspension cell cultures. Hence, BIS1 might be a metabolic engineering tool to produce sustainably high-value MIAs in C. roseus plants or cultures.


Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Identification of nuclear target proteins for S-nitrosylation in pathogen-treated Arabidopsis thaliana cell cultures

Identification of nuclear target proteins for S-nitrosylation in pathogen-treated Arabidopsis thaliana cell cultures | Plant-Microbe Interaction | Scoop.it
Highlights



117 nuclear proteins were identified as targets for S-nitrosylation.


Nuclear proteins involved in protein and RNA metabolism are the dominant targets.


In these target proteins 155 S-nitrosylation sites were predicted.


S-Nitrosylation of plant-specific histone deacetylases was demonstrated.

Abstract

Nitric oxide (NO) is a significant signalling molecule involved in the regulation of many different physiological processes in plants. One of the most imperative regulatory modes of action of NO is protein S-nitrosylation—the covalent attachment of an NO group to the sulfur atom of cysteine residues. In this study, we focus on S-nitrosylation of Arabidopsis nuclear proteins after pathogen infection. After treatment of Arabidopsis suspension cell cultures with pathogens, nuclear proteins were extracted and treated with the S-nitrosylating agent S-nitrosoglutathione (GSNO). A biotin switch assay was performed and biotin-labelled proteins were purified by neutravidin affinity chromatography and identified by mass spectrometry. A total of 135 proteins were identified, whereas nuclear localization has been described for 122 proteins of them. 117 of these proteins contain at least one cysteine residue. Most of the S-nitrosylated candidates were involved in protein and RNA metabolism, stress response, and cell organization and division. Interestingly, two plant-specific histone deacetylases were identified suggesting that nitric oxide regulated epigenetic processes in plants. In sum, this work provides a new collection of targets for protein S-nitrosylation in Arabidopsis and gives insight into the regulatory function of NO in the nucleus during plant defense response. Moreover, our data extend the knowledge on the regulatory function of NO in events located in the nucleus.

Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Use of enhancer trapping to identify pathogen-induced regulatory events spatially restricted to plant-microbe interaction sites

Use of enhancer trapping to identify pathogen-induced regulatory events spatially restricted to plant-microbe interaction sites | Plant-Microbe Interaction | Scoop.it
Plant genes differentially expressed during plant/pathogen interactions can be important for host immunity or contribute to pathogen virulence. Large-scale transcript profiling studies, such as microarray- or mRNA-seq-based analyses, have revealed hundreds of genes that are differentially expressed during plant/pathogen interactions. However, transcriptional responses limited to a small number of cells at infection sites can be difficult to detect by these approaches, as they are under-represented in the whole tissue data sets typically generated by such methods. This study examined interactions between Arabidopsis thaliana (Arabidopsis) and the pathogenic oomycete Hyaloperonospora arabidopsidis (Hpa) by enhancer trapping to uncover novel plant genes involved in local infection responses. We screened a β-glucoronidase (GUS) reporter-based enhancer-trap population for expression patterns related to Hpa infection. Several independent lines exhibited GUS expression in leaf mesophyll cells surrounding Hpa structures, indicating a regulatory response to pathogen infection. One of these lines contains a single enhancer-trap insertion in an exon of At1g08800 (MyoB1, Myosin Binding Protein 1) and was subsequently found to exhibit reduced susceptibility to Hpa. Two additional Arabidopsis lines with T-DNA insertions in exons of MyoB1 also exhibited approximately 30% fewer spores than wild type plants. This study demonstrates that our enhancer-trapping strategy can result in the identification of functionally-relevant pathogen-responsive genes. Our results further suggest that MyoB1 either positively contributes to Hpa virulence or negatively affects host immunity against this pathogen.

Via Christophe Jacquet
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Rescooped by Guogen Yang from Plants and Microbes
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Scientific Reports: Function and evolution of Magnaporthe oryzae avirulence gene AvrPib responding to the rice blast resistance gene Pib (2015)

Scientific Reports: Function and evolution of Magnaporthe oryzae avirulence gene AvrPib responding to the rice blast resistance gene Pib (2015) | Plant-Microbe Interaction | Scoop.it

Magnaporthe oryzae (Mo) is the causative pathogen of the damaging disease rice blast. The effector gene AvrPib, which confers avirulence to host carrying resistance gene Pib, was isolated via map-based cloning. The gene encodes a 75-residue protein, which includes a signal peptide. Phenotyping and genotyping of 60 isolates from each of five geographically distinct Mo populations revealed that the frequency of virulent isolates, as well as the sequence diversity within the AvrPib gene increased from a low level in the far northeastern region of China to a much higher one in the southern region, indicating a process of host-driven selection. Resequencing of the AvrPiballele harbored by a set of 108 diverse isolates revealed that there were four pathoways, transposable element (TE) insertion (frequency 81.7%), segmental deletion (11.1%), complete absence (6.7%), and point mutation (0.6%), leading to loss of the avirulence function. The lack of any TE insertion in a sample of non-rice infecting Moisolates suggested that it occurred after the host specialization of Mo. Both the deletions and the functional point mutation were confined to the signal peptide. The reconstruction of 16 alleles confirmed seven functional nucleotide polymorphisms for the AvrPiballeles, which generated three distinct expression profiles.


Via Kamoun Lab @ TSL
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Bradyrhizobium BclA is a peptide transporter required for bacterial differentiation in symbiosis with Aeschynomene legume

Bradyrhizobium BclA is a peptide transporter required for bacterial differentiation in symbiosis with Aeschynomene legume | Plant-Microbe Interaction | Scoop.it
Nodules of legume plants are highly integrated symbiotic systems shaped by millions of years of evolution. They harbor nitrogen fixing rhizobium bacteria called bacteroids. Several legume species produce peptides called NCRs in the symbiotic nodule cells which house the bacteroids. NCRs are related to antimicrobial peptides of innate immunity. They induce the endosymbionts into a differentiated, enlarged and polyploid state. The bacterial symbionts on their side evolved functions for the response to the NCR peptides. Here we identified the bclA gene of Bradyrhizobium strains ORS278 and ORS285 which is required for the formation of differentiated and functional bacteroids in the nodules of the NCR-producing Aeschynomene legumes. The BclA ABC transporter promotes the import of NCR peptides and provides protection against the antimicrobial activity of these peptides. Moreover, BclA can complement the role of the related BacA transporter of Sinorhizobium meliloti which has a similar symbiotic function in the interaction with Medicago legumes.

Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Changing SERKs and priorities during plant life: Trends in Plant Science

Changing SERKs and priorities during plant life: Trends in Plant Science | Plant-Microbe Interaction | Scoop.it
SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASES (SERKs) are coreceptors for diverse extracellular signals. SERKs are involved in a wide array of developmental and immune related processes first discovered in Arabidopsis. Recent work demonstrates the evolutionary conservation of SERKs in all multicellular plants, and highlights their functional conservation in monocots and dicots.

Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant-microbe interaction
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Chloroplast Stromules Function during Innate Immunity: Developmental Cell

Chloroplast Stromules Function during Innate Immunity: Developmental Cell | Plant-Microbe Interaction | Scoop.it

•Chloroplast stromules are induced during plant immune responses•Pro-PCD signals such as SA and H2O2 induce stromules•Stromules form dynamic connections with nucleus during immune responses•Constitutively induced stromules enhance PCD during plant immune responses

 

Summary

Inter-organellar communication is vital for successful innate immune responses that confer defense against pathogens. However, little is known about how chloroplasts, which are a major production site of pro-defense molecules, communicate and coordinate with other organelles during defense. Here we show that chloroplasts send out dynamic tubular extensions called stromules during innate immunity or exogenous application of the pro-defense signals, hydrogen peroxide (H2O2) and salicylic acid. Interestingly, numerous stromules surround nuclei during defense response, and these connections correlate with an accumulation of chloroplast-localized NRIP1 defense protein and H2O2 in the nucleus. Furthermore, silencing and knockout ofchloroplast unusual positioning 1 (CHUP1) that encodes a chloroplast outer envelope protein constitutively induces stromules in the absence of pathogen infection and enhances programmed cell death. These results support a model in which stromules aid in the amplification and/or transport of pro-defense signals into the nucleus and other subcellular compartments during immunity.


Via Jennifer Mach, Suayib Üstün
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Rescooped by Guogen Yang from Plant-Microbe Symbioses
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Chromatin-based control of effector gene expression in plant-associated fungi

Plant-associated fungi often present in their genome areas enriched in repeat sequences and effector genes, the latter being specifically induced in planta. The location of effector genes in regions enriched in repeats has been shown to have an impact on adaptability of fungi but could also provide for tight control of effector gene expression through chromatin-based regulation. The distribution of two repressive histone marks was shown to be an important regulatory layer in two fungal species with different lifestyles. Chromatin-based control of effector gene expression is likely to provide an evolutionary advantage by preventing the expression of genes not needed during vegetative growth and allow for a massive concerted expression at particular time-points of plant infection.

Via Jean-Michel Ané
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Rescooped by Guogen Yang from Virology and Bioinformatics from Virology.ca
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Plant virus replication and movement

Plant virus replication and movement | Plant-Microbe Interaction | Scoop.it
Because plant cells are not identical to animal cells, plant viruses are significantly different from animal viruses in several ways.

Via Ed Rybicki
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Rescooped by Guogen Yang from Plants and Microbes
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Journal of Integrative Plant Biology: Viroids: Small Probes for Exploring the Vast Universe of RNA Trafficking in Plants (2010)

Journal of Integrative Plant Biology: Viroids: Small Probes for Exploring the Vast Universe of RNA Trafficking in Plants (2010) | Plant-Microbe Interaction | Scoop.it

Cell-to-cell and long-distance trafficking of RNA is a rapidly evolving frontier of integrative plant biology that broadly impacts studies on plant growth and development, spread of infectious agents and plant defense responses. The fundamental questions being pursued at the forefronts revolve around function, mechanism and evolution. In the present review, we will first use specific examples to illustrate the biological importance of cell-to-cell and long-distance trafficking of RNA. We then focus our discussion on research findings obtained using viroids that have advanced our understanding of the underlying mechanisms involved in RNA trafficking. We further use viroid examples to illustrate the great diversity of trafficking machinery evolved by plants, as well as the promise for new insights in the years ahead. Finally, we discuss the prospect of integrating findings from different experimental systems to achieve a systems-based understanding of RNA trafficking function, mechanism and evolution.


Via Kamoun Lab @ TSL
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Rescooped by Guogen Yang from Effectors and Plant Immunity
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Front. Plant Sci.: MorTAL Kombat: the story of defense against TAL effectors through loss-of-susceptibility (2015)

Front. Plant Sci.: MorTAL Kombat: the story of defense against TAL effectors through loss-of-susceptibility (2015) | Plant-Microbe Interaction | Scoop.it

Many plant-pathogenic xanthomonads rely on Transcription Activator-Like (TAL) effectors to colonize their host. This particular family of type III effectors functions as specific plant transcription factors via a novel programmable DNA-binding domain. Upon binding to the promoters of plant disease susceptibility genes in a sequence-specific manner, the expression of these host genes is induced. However, plants have evolved specific strategies to counter the action of TAL effectors and confer resistance. One mechanism is to avoid the binding of TAL effectors by mutations of their DNA binding sites, resulting in resistance by loss-of-susceptibility. This article reviews our current knowledge of the susceptibility hubs targeted by Xanthomonas TAL effectors, possible evolutionary scenarios for plants to combat the pathogen with loss-of-function alleles, and how this knowledge can be used overall to develop new pathogen-informed breeding strategies and improve crop resistance.

 

Hutin M, Pérez-Quintero AL, Lopez C and Szurek B


Via Nicolas Denancé
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Rescooped by Guogen Yang from Virology and Bioinformatics from Virology.ca
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PLOS Computational Biology: Ten Years of PLoS‡ Computational Biology: A Decade of Appreciation and Innovation

PLOS Computational Biology: Ten Years of PLoS‡ Computational Biology: A Decade of Appreciation and Innovation | Plant-Microbe Interaction | Scoop.it

Via Chad Smithson
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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TRANSCRIPTION ACTIVATOR-LIKE EFFECTOR NUCLEASE-Mediated Generation and Metabolic Analysis of Camalexin-Deficient cyp71a12 cyp71a13 Double Knockout Lines

TRANSCRIPTION ACTIVATOR-LIKE EFFECTOR NUCLEASE-Mediated Generation and Metabolic Analysis of Camalexin-Deficient cyp71a12 cyp71a13 Double Knockout Lines | Plant-Microbe Interaction | Scoop.it

In Arabidopsis (Arabidopsis thaliana), a number of defense-related metabolites are synthesized via indole-3-acetonitrile (IAN), including camalexin and indole-3-carboxylic acid (ICOOH) derivatives. Cytochrome P450 71A13 (CYP71A13) is a key enzyme for camalexin biosynthesis and catalyzes the conversion of indole-3-acetaldoxime (IAOx) to IAN. The CYP71A13 gene is located in tandem with its close homolog CYP71A12, also encoding an IAOx dehydratase. However, for CYP71A12, indole-3-carbaldehyde and cyanide were identified as major reaction products. To clarify CYP71A12 function in vivo and to better understand IAN metabolism, we generated two cyp71a12 cyp71a13 double knockout mutant lines. CYP71A12-specific transcription activator-like effector nucleases were introduced into the cyp71a13 background, and very efficient somatic mutagenesis was achieved. We observed stable transmission of the cyp71a12 mutation to the following generations, which is a major challenge for targeted mutagenesis in Arabidopsis. In contrast to cyp71a13 plants, in which camalexin accumulation is partially reduced, double mutants synthesized only traces of camalexin, demonstrating that CYP71A12 contributes to camalexin biosynthesis in leaf tissue. A major role of CYP71A12 was identified for the inducible biosynthesis of ICOOH. Specifically, the ICOOH methyl ester was reduced to 12% of the wild-type level in AgNO3-challenged cyp71a12 leaves. In contrast, indole-3-carbaldehyde derivatives apparently are synthesized via alternative pathways, such as the degradation of indole glucosinolates. Based on these results, we present a model for this surprisingly complex metabolic network with multiple IAN sources and channeling of IAOx-derived IAN into camalexin biosynthesis. In conclusion, transcription activator-like effector nuclease-mediated mutation is a powerful tool for functional analysis of tandem genes in secondary metabolism.


Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Homeologs of the Nicotiana benthamiana Antiviral ARGONAUTE1 Show Different Susceptibilities to microRNA168-Mediated Control

Homeologs of the Nicotiana benthamiana Antiviral ARGONAUTE1 Show Different Susceptibilities to microRNA168-Mediated Control | Plant-Microbe Interaction | Scoop.it
The plant ARGONAUTE1 protein (AGO1) is a central functional component of the posttranscriptional regulation of gene expression and the RNA silencing-based antiviral defense. By genomic and molecular approaches, we here reveal the presence of two homeologs of the AGO1-like gene in Nicotiana benthamiana, NbAGO1-1H and NbAGO1-1L. Both homeologs retain the capacity to transcribe messenger RNAs (mRNAs), which mainly differ in one 18-nucleotide insertion/deletion (indel). The indel does not modify the frame of the open reading frame, and it is located eight nucleotides upstream of the target site of a microRNA, miR168, which is an important modulator of AGO1 expression. We demonstrate that there is a differential accumulation of the two NbAGO1-1 homeolog mRNAs at conditions where miR168 is up-regulated, such as during a tombusvirus infection. The data reported suggest that the indel affects the miR168-guided regulation of NbAGO1 mRNA. The two AGO1 homeologs show full functionality in reconstituted, catalytically active RNA-induced silencing complexes following the incorporation of small interfering RNAs. Virus-induced gene silencing experiments suggest a specific involvement of the NbAGO1 homeologs in symptom development. The results provide an example of the diversity of microRNA target regions in NbAGO1 homeolog genes, which has important implications for improving resilience measures of the plant during viral infections.

Via Christophe Jacquet
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Rescooped by Guogen Yang from How microbes emerge
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Fungal Traits That Drive Ecosystem Dynamics on Land

Fungal Traits That Drive Ecosystem Dynamics on Land | Plant-Microbe Interaction | Scoop.it

Fungi contribute extensively to a wide range of ecosystem processes, including decomposition of organic carbon, deposition of recalcitrant carbon, and transformations of nitrogen and phosphorus. In this review, we discuss the current knowledge about physiological and morphological traits of fungi that directly influence these processes, and we describe the functional genes that encode these traits. In addition, we synthesize information from 157 whole fungal genomes in order to determine relationships among selected functional genes within fungal taxa. Ecosystem-related traits varied most at relatively coarse taxonomic levels. For example, we found that the maximum amount of variance for traits associated with carbon mineralization, nitrogen and phosphorus cycling, and stress tolerance could be explained at the levels of order to phylum. Moreover, suites of traits tended to co-occur within taxa. Specifically, the genetic capacities for traits that improve stress tolerance—β-glucan synthesis, trehalose production, and cold-induced RNA helicases—were positively related to one another, and they were more evident in yeasts. Traits that regulate the decomposition of complex organic matter—lignin peroxidases, cellobiohydrolases, and crystalline cellulases—were also positively related, but they were more strongly associated with free-living filamentous fungi. Altogether, these relationships provide evidence for two functional groups: stress tolerators, which may contribute to soil carbon accumulation via the production of recalcitrant compounds; and decomposers, which may reduce soil carbon stocks. It is possible that ecosystem functions, such as soil carbon storage, may be mediated by shifts in the fungal community between stress tolerators and decomposers in response to environmental changes, such as drought and warming.


Via Steve Marek, Niklaus Grunwald
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Rescooped by Guogen Yang from Plant-Microbe Symbioses
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Maternal effects on tree phenotypes: considering the microbiome

Maternal effects on tree phenotypes: considering the microbiome | Plant-Microbe Interaction | Scoop.it
The biotic and abiotic environmental experience of plants can influence the offspring without any changes in DNA sequence. These effects can modulate the development of the progeny and their interaction with microorganisms. This interaction includes fungal endophytic communities which have significant effects on trees and their associated ecosystems. In this opinion article, we highlight potential maternal mechanisms through which endophytes could influence the progeny. We argue that a better understanding of these interactions might help to predict the response of trees to stress conditions and enhance the efficiency of tree breeding programs.

Via Christophe Jacquet, Jean-Michel Ané
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Rescooped by Guogen Yang from Plants and Microbes
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Plant J: Crystal structure of the effector AvrLm4-7 of Leptosphaeria maculans reveals insights into its translocation into plant cell and recognition by resistance proteins (2015)

Plant J: Crystal structure of the effector AvrLm4-7 of Leptosphaeria maculans reveals insights into its translocation into plant cell and recognition by resistance proteins (2015) | Plant-Microbe Interaction | Scoop.it

The avirulence gene AvrLm4-7 of Leptosphaeria maculans, the causal agent of stem canker of oilseed rape, confers a dual specificity of recognition by two resistance genes (Rlm4 and Rlm7) and is strongly involved in fungal fitness. In order to elucidate the biological function of AvrLm4-7 and understand the specificity of recognition by Rlm4 and Rlm7, the AvrLm4-7 protein was produced in Pichia pastoris and its crystal structure determined. It revealed the presence of four disulfide bridges but no close structural analogs could be identified. A short stretch of amino acids in the C-terminus of the protein, (R/N)(Y/F)(R/S)E(F/W), was well-conserved among AvrLm4-7 homologs. Loss of recognition of AvrLm4-7 by Rlm4 is due to mutation of a single glycine to an arginine residue located in a loop of the protein. Loss of recognition by Rlm7 is governed by more complex mutational patterns, including gene loss or drastic modifications of the protein structure. Three point mutations altered residues in the well-conserved C-terminal motif or close to the glycine involved in Rlm4-mediated recognition, resulted in a loss of Rlm7-mediated recognition. Transient expression in tobacco and particle bombardment experiments on oilseed rape leaves suggested that AvrLm4-7 interacts with its cognate R proteins inside the plant cell, and can be translocated into plant cells in the absence of the pathogen. Translocation of AvrLm4-7 into oilseed rape leaves likely requires the (R/N)(Y/F)(R/S)E(F/W) motif as well as a RAWG motif located in a nearby loop that together form a positively charged region.


Via Kamoun Lab @ TSL
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Role of plant growth regulators as chemical signals in plant–microbe interactions: a double edged sword

Role of plant growth regulators as chemical signals in plant–microbe interactions: a double edged sword | Plant-Microbe Interaction | Scoop.it
Highlights



Plant defense signaling pathways overlap and can act synergistically or antagonistically.


ABA is known for its role in abiotic stress response but also plays a role in defense.


ABA can positively or negatively impact plant resistance; usually high ABA levels lower resistance.


Fungi also produce ABA.


ABA may play a role in enhancing or accelerating fungal virulence.

Growth regulators act not only as chemicals that modulate plant growth but they also act as signal molecules under various biotic and abiotic stresses. Of all growth regulators, abscisic acid (ABA) is long known for its role in modulating plants response against both biotic and abiotic stress. Although the genetic information for ABA biosynthesis in plants is well documented, the knowledge about ABA biosynthesis in other organisms is still in its infancy. It is known that various microbes including bacteria produce and secrete ABA, but the overall functional significance of why ABA is synthesized by microbes is not known. Here we discuss the functional involvement of ABA biosynthesis by a pathogenic fungus. Furthermore, we propose that ABA biosynthesis in plant pathogenic fungi could be targeted for novel fungicidal discovery.

Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Plant cysteine-rich peptides that inhibit pathogen growth and control rhizobial differentiation in legume nodules

Plant cysteine-rich peptides that inhibit pathogen growth and control rhizobial differentiation in legume nodules | Plant-Microbe Interaction | Scoop.it

Highlights•

Medicago truncatula has both typical defensins and defensin-like peptides.

Nodule Cys-rich peptides (NCRs) comprise the majority of defensin-like peptides in M. truncatula.

NCRs are plant effectors governing rhizobial bacteroid development in nodules.

Phylogenetic relatedness of defensins and NCRs is assessed.

Plants must co-exist with both pathogenic and beneficial microbes. Antimicrobial peptides with broad antimicrobial activities represent one of the first lines of defense against pathogens. Many plant cysteine-rich peptides with potential antimicrobial properties have been predicted. Amongst them, defensins and defensin-like peptides are the most abundant and plants can express several hundreds of them. In some rhizobial–legume symbioses special defensin-like peptides, the nodule-specific cysteine-rich (NCR) peptides have evolved in those legumes whose symbiotic partner terminally differentiates. In Medicago truncatula, >700 NCRs exist and collectively act as plant effectors inducing irreversible differentiation of rhizobia to nitrogen-fixing bacteroids. Cationic NCR peptides have a broad range of potent antimicrobial activities but do not kill the endosymbionts.


Via Christophe Jacquet
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Rescooped by Guogen Yang from The science toolbox
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Promoting an open research culture

Promoting an open research culture | Plant-Microbe Interaction | Scoop.it

Transparency, openness, and reproducibility are readily recognized as vital features of science (1, 2). When asked, most scientists embrace these features as disciplinary norms and values (3). Therefore, one might expect that these valued features would be routine in daily practice. Yet, a growing body of evidence suggests that this is not the case (4–6).

A likely culprit for this disconnect is an academic reward system that does not sufficiently incentivize open practices (7). In the present reward system, emphasis on innovation may undermine practices that support verification. Too often, publication requirements (whether actual or perceived) fail to encourage transparent, open, and reproducible science (2, 4, 8, 9). For example, in a transparent science, both null results and statistically significant results are made available and help others more accurately assess the evidence base for a phenomenon. In the present culture, however, null results are published less frequently than statistically significant results (10) and are, therefore, more likely inaccessible and lost in the “file drawer” (11).


Via Niklaus Grunwald
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Chitin-mediated plant–fungal interactions: catching, hiding and handshaking

Chitin-mediated plant–fungal interactions: catching, hiding and handshaking | Plant-Microbe Interaction | Scoop.it

Highlights•

Plants recognize infecting fungi through the perception of released chitin fragments by LysM receptor complexes.

Pathogenic fungi secrete effectors and change their cell walls to escape from the chitin-mediated immune system.

Chitin-related molecules also serve as symbiotic signals in rhizobium/AM symbiosis.

Dual function of OsCERK1 in both chitin-mediated immunity and AM symbiosis sheds a new light on the evolutionary relationships between these systems.

Plants can detect infecting fungi through the perception of chitin oligosaccharides by lysin motif receptors such as CEBiP and CERK1. A major function of CERK1 seems to be as a signaling molecule in the receptor complex formed with ligand-binding molecules and to activate downstream defense signaling. Fungal pathogens, however, have developed counter strategies to escape from the chitin-mediated detection by using effectors and/or changing their cell walls. Common structural features between chitin and Nod-/Myc-factors and corresponding receptors have suggested the close relationships between the chitin-mediated immunity and rhizobial/arbuscular mycorrhizal symbiosis. The recent discovery of the dual function of OsCERK1 in both plant immunity and mycorrhizal symbiosis sheds new light on the evolutionary relationships between defense and symbiotic systems in plants.

Current Opinion in Plant Biology 2015, 26:xx–


Via Christophe Jacquet
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