Abstract

WRKY transcription factors belong to a superfamily that is involved in many important biological processes, including plant development and senescence. However, little is known about the transcriptional regulation mechanisms of WRKY genes involved in kiwifruit postharvest ripening. Here, we isolated a WRKY gene from the kiwifruit genome and named it AcWRKY40 . AcWRKY40 is a nucleus-localized protein that possesses transcriptional activation activity. The expression of AcWRKY40 was detected, and the gene responded to ethylene treatment during kiwifruit postharvest ripening, indicating its involvement in this process at the transcriptional level. We found multiple cis -acting elements related to maturation and senescence in the AcWRKY40 promoter. GUS activity analysis showed that its promoter activity was induced by exogenous ethylene. Yeast one-hybrid and dual-luciferase assays demonstrated that AcWRKY40 binds to the promoters of AcSAM2 , AcACS1 , and AcACS2 to activate them. In addition, transient transformations showed that AcWRKY40 enhances the expression of AcSAM2 , AcACS1 , and AcACS2 . Taken together, these results suggest that AcWRKY40 is involved in kiwifruit postharvest ripening, possibly by regulating the expression of genes related to ethylene biosynthesis, thus deepening our understanding of the regulatory mechanisms of WRKY transcription factors in fruit ripening.