Transcription factor CsWRKY76 potentially involved in accumulation of scoparone and pentamethoxyflavone in citrus fruit stimulated by salicylic acid

Salicylic acid (SA) is a potent elicitor of phytoalexins in citrus fruit, yet the transcriptional regulatory mechanisms underlying SA-induced disease resistance remain unclear. Here, we identified CsWRKY76 as a key transcription factor (TF) positively regulating SA-mediated accumulation of scoparone and 3, 5, 7, 3′, 4′-pentamethoxyflavone (PMF) in citrus (Citrus sinensis) peels inoculated with Penicillium italicum. CsWRKY76 expression was strongly correlated with phytoalexin levels and significantly upregulated by SA. Subcellular localization confirmed its nuclear targeting, while yeast one-hybrid (Y1H) assay revealed transcriptional activation and specific binding to the W-box motif. Transient overexpression of CsWRKY76 in citrus peels elevated scoparone (74.8 %) and PMF (24.3 %) levels, concomitant with upregulation of phenylpropanoid pathway genes (Cs4CL, CsPAL, CsF6'H1, CsCOMT). Conversely, silencing CsWRKY76 reduced scoparone and PMF accumulation by 49.7 % and 57.8 % with downregulation of the involved genes. Notably, CsWRKY76 indirectly regulated these biosynthetic genes, suggesting a complex regulatory network. Our findings elucidate CsWRKY76 as a critical regulator of SA-induced defense responses in citrus, providing a molecular target for enhancing postharvest disease resistance.