FaMYB5 Interacts with FaBBX24 to Regulate Anthocyanin and Proanthocyanidin Biosynthesis in Strawberry ( Fragaria × ananassa ).

MYB and BBX transcription factors play important roles in flavonoid biosynthesis. Here, we obtained transgenic woodland strawberry with stable overexpression of FaMYB5 , demonstrating that FaMYB5 can increase anthocyanin and proanthocyanidin content in roots, stems and leaves of woodland strawberry. In addition, bimolecular fluorescence complementation assays and yeast two-hybridization demonstrated that the N-terminal (1-99aa) of FaBBX24 interacts with FaMYB5. Transient co-expression of FaBBX24 and FaMYB5 in cultivated strawberry 'Xiaobai' showed that co-expression strongly promoted the expression of F3'H , 4CL-2 , TT12 , AHA10 and ANR and then increased the content of anthocyanin and proanthocyanidin in strawberry fruits. We also determined that FaBBX24 is also a positive regulator of anthocyanin and proanthocyanidin biosynthesis in strawberry. The results reveal a novel mechanism by which the FaMYB5-FaBBX24 module collaboratively regulates anthocyanin and proanthocyanidin in strawberry fruit.