Résumé
Grapevine organs accumulate anthocyanins in a cultivar-specific and environmentally induced manner.The MYBA1-A2 genes within the berry color locus in chromosome 2 represent the major genetic determinantsof fruit color. The simultaneous occurrence of transposon insertions and point mutations in thesegenes is responsible for most white-skinned phenotypes; however, the red pigmentation found in vegetativeorgans suggests the presence of additional regulators. This work describes a genomic region ofchromosome 14 containing three closely related R2R3-MYB genes, named MYBA5, MYBA6 and MYBA7.Ectopic expression of the latter two genes in grapevine hairy roots promoted anthocyanin accumulationwithout affecting other phenylpropanoids. Transcriptomic profiling of hairy roots expressing MYBA1,MYBA6 and MYBA7 showed that these regulators share the activation of late biosynthetic and modification/transport-related genes, but differ in the activation of the FLAVONOID-3050-HYDROXYLASE (F3050H)family. An alternatively spliced MYBA6 variant was incapable of activating anthocyanin synthesis, however,because of the lack of an MYC1 interaction domain. MYBA1, MYBA6.1 and MYBA7 activated thepromoters of UDP-GLUCOSE:FLAVONOID 3-O-GLUCOSYLTRANSFERASE (UFGT) and ANTHOCYANIN 3-OGLUCOSIDE-6″-O-ACYLTRANSFERASE (3AT), but only MYBA1 induced F3050H in concordance with thelow proportion of tri-hydroxylated anthocyanins found in MYBA6-A7 hairy roots. This putative new colorlocus is related to the red/cyanidic pigmentation of vegetative organs in black- and white-skinned cultivars,and forms part of the UV-B radiation response pathway orchestrated by ELONGATEDHYPOCOTYL 5 (HY5). These results demonstrate the involvement of additional anthocyanin regulators ingrapevine and suggest an evolutionary divergence between the two grape color loci for controlling additionaltargets of the flavonoid pathway.