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The transcription factor WRKY75 positively regulates jasmonate-mediated plant defense to necrotrophic fungal pathogens.

ABSTRACT: Necrotrophic fungi cause devastating diseases in both horticultural and agronomic crops, but our understanding of plant defense responses against these pathogens is still limited. In this study, we demonstrated that WRKY75 positively regulates jasmonate (JA)-mediated plant defense against necrotrophic fungal pathogens Botrytis cinerea and Alternaria brassicicola, and also affects the sensitivity of plants to JA-inhibited seed germination and root growth. Quantitative analysis indicated that several JA-associated genes, such as OCTADECANOID-RESPONSIVE ARABIDOPSIS (ORA59) and PLANT DEFENSIN 1.2A (PDF1.2), were significantly reduced in expression in wrky75 mutants, and enhanced in WRKY75 overexpressing transgenic plants. Immunoprecipitation assays revealed that WRKY75 directly binds to the promoter of ORA59 and represses itstranscription. In vivo and in vitro experiments suggested that WRKY75 interacts with several JASMONATE ZIM-domain proteins, repressors of the JA signaling pathway. We determined that JASMONATE-ZIM-DOMAIN PROTEIN 8 (JAZ8) represses the transcriptional function of WRKY75, thereby attenuating the expression of its regulation. Overexpression of JAZ8 repressed plant defense responses to B. cinerea. Our study provides evidence that WRKY75 functions as a critical component of the JA-mediated signaling pathway to positively regulate Arabidopsis defense responses to necrotrophic pathogens.

SUBMITTER: Chen L

PROVIDER: S-EPMC7904156 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

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The transcription factor WRKY75 positively regulates jasmonate-mediated plant defense to necrotrophic fungal pathogens.

Chen Ligang L Zhang Liping L Xiang Shengyuan S Chen Yanli Y Zhang Haiyan H Yu Diqiu D

Journal of experimental botany 20210201 4

Necrotrophic fungi cause devastating diseases in both horticultural and agronomic crops, but our understanding of plant defense responses against these pathogens is still limited. In this study, we demonstrated that WRKY75 positively regulates jasmonate (JA)-mediated plant defense against necrotrophic fungal pathogens Botrytis cinerea and Alternaria brassicicola, and also affects the sensitivity of plants to JA-inhibited seed germination and root growth. Quantitative analysis indicated that seve ...[more]

PMID: 33165597

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Project description:Botrytis cinerea is the causal agent of gray mold diseases in a range of dicotyledonous plant species. The fungus can reproduce asexually by forming macroconidia for dispersal and sclerotia for survival; the latter also participate in sexual reproduction by bearing the apothecia after fertilization by microconidia. Light induces the differentiation of conidia and apothecia, while sclerotia are exclusively formed in the absence of light. The relevance of light for virulence of the fungus is not obvious, but infections are observed under natural illumination as well as in constant darkness. By a random mutagenesis approach, we identified a novel virulence-related gene encoding a GATA transcription factor (BcLTF1 for light-responsive TF1) with characterized homologues in Aspergillus nidulans (NsdD) and Neurospora crassa (SUB-1). By deletion and over-expression of bcltf1, we confirmed the predicted role of the transcription factor in virulence, and discovered furthermore its functions in regulation of light-dependent differentiation, the equilibrium between production and scavenging of reactive oxygen species (ROS), and secondary metabolism. Microarray analyses revealed 293 light-responsive genes, and that the expression levels of the majority of these genes (66%) are modulated by BcLTF1. In addition, the deletion of bcltf1 affects the expression of 1,539 genes irrespective of the light conditions, including the overexpression of known and so far uncharacterized secondary metabolism-related genes. Increased expression of genes encoding alternative respiration enzymes, such as the alternative oxidase (AOX), suggest a mitochondrial dysfunction in the absence of bcltf1. The hypersensitivity of Δbctlf1 mutants to exogenously applied oxidative stress--even in the absence of light--and the restoration of virulence and growth rates in continuous light by antioxidants, indicate that BcLTF1 is required to cope with oxidative stress that is caused either by exposure to light or arising during host infection.

Project description:BACKGROUND: To survive herbivore attack, plants have evolved potent mechanisms of mechanical or chemical defense that are either constitutively present or inducible after herbivore attack. Due to the costs of defense deployment, plants often regulate their biosynthesis using various transcription factors (TFs). MYC2 regulators belong to the bHLH family of transcription factors that are involved in many aspects of plant defense and development. In this study, we identified a novel MYC2 TF from N. attenuata and characterized its regulatory function using a combination of molecular, analytic and ecological methods. RESULTS: The transcript and targeted metabolite analyses demonstrated that NaMYC2 is mainly involved in the regulation of the biosynthesis of nicotine and phenolamides in N. attenuata. In addition, using broadly-targeted metabolite analysis, we identified a number of other metabolite features that were regulated by NaMYC2, which, after full annotation, are expected to broaden our understanding of plant defense regulation. Unlike previous reports, the biosynthesis of jasmonates and some JA-/NaCOI1-dependent metabolites (e.g. HGL-DTGs) were not strongly regulated by NaMYC2, suggesting the involvement of other independent regulators. No significant differences were observed in the performance of M. sexta on MYC2-silenced plants, consistent with the well-known ability of this specialist insect to tolerate nicotine. CONCLUSION: By regulating the biosynthesis of nicotine, NaMYC2 is likely to enhance plant resistance against non-adapted herbivores and contribute to plant fitness; however, multiple JA/NaCOI1-dependent mechanisms (perhaps involving other MYCs) that regulate separate defense responses are likely to exist in N. attenuata. The considerable variation observed amongst different plant families in the responses regulated by jasmonate signaling highlights the sophistication with which plants craft highly specific and fine-tuned responses against the herbivores that attack them.

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The transcription factor WRKY75 positively regulates jasmonate-mediated plant defense to necrotrophic fungal pathogens.

Publications

The transcription factor WRKY75 positively regulates jasmonate-mediated plant defense to necrotrophic fungal pathogens.

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