Are VvMYB5A and VvMYB5B regulators of grape flavonoid pathway?

I grapevine the biosynthesis of flavonoids in highly regulated in order that different compounds are produced in different organs and stages of development. Despite the flavonoid pathway has been well studied little is known about the transcriptional machanism that regulates it. Recent studies suggest that two MYB transcription factors, VvMYB5a and VvMYB5b are responsible for the regulation of the early flavonoid structural genes in different syages of berry development. In petunia the mutation of the ortholog of VvMYB5a and VvMYB5b (PH4) results in the increase of vacuolar pH and in blue shift of the flover color. We used functional complementation analyses of some well characterized petunia anthocyanin/pH regulatory mutants