WRKY45 is a negative regulator of Botrytis cinerea resistance through the JA/ET signaling pathway in Arabidopsis

<i>Botrytis cinerea</i> is a necrotrophic fungal pathogen that causes significant crop damage, yet the molecular mechanisms underlying plant defense remain incompletely understood. Here, we identify WRKY45 as a negative regulator of <i>Arabidopsis</i> resistance to <i>B. cinerea</i> through the suppression of JA/ET-mediated defense signaling. Our results show that <i>WRKY45</i> expression was induced by <i>B. cinerea</i> infection, peaking 48 hours post-inoculation. Loss of <i>WRKY45</i> function enhanced resistance, while <i>WRKY45</i> overexpression increased susceptibility and cellular damage, as indicated by elevated electrolyte leakage, higher malondialdehyde levels, and reduced chlorophyll content. RNA-seq analysis identified 1,850 differentially expressed genes in <i>wrky45</i> mutants, with strong enrichment of JA/ET-responsive pathways. Defense-related genes, including <i>ORA59</i>, <i>PDF1.2</i>, <i>ERF104</i>, and <i>ERF1</i>, were markedly upregulated in <i>wrky45</i> but suppressed in overexpression lines, as confirmed by qRT-PCR. Electrophoretic mobility shift assays and dual-luciferase assays demonstrated that WRKY45 directly binds to the <i>ORA59</i> promoter inhibiting its transcription, and represses the expression of <i>PDF1.2</i>, <i>ERF104</i>, and <i>ERF1</i>. Together, these results show that WRKY45 functions as a negative regulator by suppressing the expression of JA/ET-mediated defense genes, thereby modulating plant resistance to <i>B. cinerea</i>.