BnaA07.WRKY40 transcription factor confers enhanced defensive response to Sclerotinia sclerotiorum in Brassica napus

Oilseed rape (Brassica napus) is one of the most important oil crops, contributing to the world's supply of vegetable oil. However, its production is severely threatened by the broad-host-range fungus Sclerotinia sclerotiorum. Despite extensive efforts, the identification of defense genes in B. napus remains limited, underscoring the urgent need to discover more robust and functional defense genes. In this study, we demonstrate that BnaA07.WRKY40 acts as a positive regulator in response to S. sclerotiorum infection. Overexpression of BnaA07.WRKY40 in B. napus markedly enhances plant defense against S. sclerotiorum. In contrast, the BnaA07.WRKY40-RNAi and knockout mutants displayed increased susceptibility. Further insights into the role of BnaA07.WRKY40 is gained through DAP-seq and RNA-seq analyses, complemented by yeast one-hybrid assay. It is revealed that BnaA07.WRKY40 regulates downstream target genes encoding Hypoxia-responsive family protein (HRP), β-1,3-glucanase 2 (BG2), Precursor of peptide 1 (PEP1), and Acyl-CoA N-acyltransferase (ACNAT) superfamily protein. Following S. sclerotiorum inoculation, the lesion areas on the leaves of mutants for these target genes were significantly larger than those on wild-type plants, indicating that knockout of these genes increased susceptibility to S. sclerotiorum. These findings provide valuable insights into the molecular mechanisms by which BnaA07.WRKY40 regulates defensive response to S. sclerotiorum.