Regulation of light-induced anthocyanin biosynthesis in sweet cherry by the WRKY transcription factor PavWRKY18.

Anthocyanin production and storage are crucial for determining the color and quality of sweet cherry (Prunus avium) fruits. Although WRKY transcription factors are recognized as critical regulators of secondary metabolism, their specific roles and underlying mechanisms regarding coloration in sweet cherry remain elusive. Through two comparative transcriptomic analysis of sweet cherry in different ripening stages and lighting treatments, we identified the candidate gene PavWRKY18. The expression patterns of PavWRKY18 exhibits specifically high expression during late fruit ripening and showed a strong positive correlation with light. With overexpression and sliencing of WRKY18 in sweet cherry fruits, functional characterization demonstrated that PavWRKY18 serves as a light-induced positive role of fruit coloration and accumulation of anthocyanin. Integrated transcriptomic analysis further revealed that fruit light-mediated related genes are significantly altered in the PavWRKY18-OE2 fruits. Molecular assays demonstrated that the PavWRKY18 protein directly binds to W-box cis-elements in the promoters of key structural genes involved in anthocyanin biosynthesis (PavCHS, PavF3H, PavDFR, and PavUFGT), thus activating their transcription. Our findings elucidate a molecular mechanism wherein light-induced PavWRKY18 positively regulates anthocyanin biosynthesis and accumulation through the direct targeting multiple structural genes, which might provide target for the breeding of enhancing the coloration of sweet cherry fruits.