AaMYB17 Regulates the Biosynthesis of Anthocyanins in the Fruit of Actinidia arguta.

To reveal the relationship of anthocyanin biosynthesis in Actinidia arguta, we cloned a typical R2R3-MYB transcription factor-AaMYB17 gene from the cultivar "Dahongpao." Expression analysis showed that AaMYB17 was significantly negatively correlated with anthocyanin accumulation and the expression of most of the structural genes in the anthocyanin biosynthetic pathway. Functional verification using transient overexpression, virus-induced gene silencing (VIGS), and heterologous expression in Arabidopsis thaliana and tomato demonstrated that AaMYB17 acts as a broad-spectrum repressor that significantly inhibits anthocyanin biosynthesis and downregulates related structural genes. We performed dual-luciferase and GUS assays, which confirmed that AaMYB17 can bind to the key anthocyanin biosynthesis gene AaANS, repress its expression, and thereby inhibit anthocyanin accumulation. This work clarifies the molecular basis through which AaMYB17 negatively regulates anthocyanin biosynthesis in Actinidia arguta. These findings also supply important gene resources and theoretical support for the molecular breeding of Actinidia arguta fruits with improved anthocyanin contents.