Strawberry WRKY Transcription Factor WRKY50 Is Required for Resistance to Necrotrophic Fungal Pathogen Botrytis cinerea

WRKY protein is one of the largest plant-specific transcription factors that plays critical roles in plant stress responses, but few WRKY transcription factors have been functionally analyzed in strawberry. In this study, a Botrytis cinerea response WRKY gene, FvWRKY50, was isolated from the woodland strawberry. Expression analysis indicated that the transcript of FvWRKY50 was gradually decreased with fruit ripening, but was significantly induced by B. cinerea infection in mature strawberry fruit. Subcellular localization assay revealed that FvWRKY50 was localized in the nucleus. Several cis-elements related to pathogen responses were observed in the promoter region of FvWRKY50. Pathogen infection assay indicated that overexpression of FvWRKY50 in strawberry fruit significantly enhanced their resistance against B. cinerea, while the silencing of FvWRKY50 dramatically compromised their disease-resistant ability. The expression levels of several genes involved in jasmonic acid (JA) biosynthesis, signaling transduction, and antimicrobial protein biosynthesis were regulated to diverse extents in FvWRKY50 overexpressed and silenced fruit. Collectively, our study inferred that FvWRKY50 is a positive regulator that mediates resistance against B. cinerea through regulating some JA pathway and defense-related genes.