AaMYB114 promotes the coloration of Actinidia arguta by synthesizing and transporting anthocyanins

BACKGROUND: Anthocyanin accumulation in plant tissues requires coordinated regulation of both biosynthesis and transport. In Actinidia arguta, these pigments determine visual quality while enhancing nutritional value and antioxidant capacity, yet the mechanisms underlying the coordinated regulation of anthocyanin synthesis and transport remain poorly understood. RESULTS: In this study, we identified AaMYB114, an R2R3-MYB transcription factor, from a skin-color-associated co-expression module in Actinidia arguta. Transient overexpression of AaMYB114 in fruit peel significantly enhanced red pigmentation and anthocyanin content. Yeast one-hybrid (Y1H) and dual-luciferase assays demonstrated that AaMYB114 directly binds to and activates the promoters of key biosynthetic genes AaPAL, AaCHI, and AaF3H. Notably, AaMYB114 also directly targets the promoter of AaGST, a glutathione S-transferase essential for anthocyanin transport into the vacuole. Co-overexpression of AaMYB114 and AaGST synergistically intensified red coloration beyond either gene alone, while chemical inhibition of GST activity with ethacrynic acid suppressed pigmentation and attenuated the effect of AaMYB114 overexpression. CONCLUSIONS: These findings establish AaMYB114 as a dual-function master regulator that simultaneously orchestrates anthocyanin biosynthesis and transport, providing both theoretical insights into pigment regulation and practical targets for molecular breeding of red-skinned kiwifruit cultivars.