Grape skin color recovery in Albariño and Verdejo somatic varians by independent regain of MYBA1 or MYBA2 function

Abstract

Spontaneous somatic mutations cause berry skin color variation in grapevine. White grape cultivars result from a Gret1 retro-transposon insertion and a frameshift deletion in VviMYBA1 and VviMybA2 anthocyanin biosynthesis genes, respectively. Here we studied the origin of two grape regain of color somatic variants appeared in Albariño and Verdejo white-berried cultivars. Targeted UPLC-QqQ-MS/MS metabolomics detected anthocyanins in the berry skin of both red variants, but at higher levels in red Albariño that was the only variant accumulating tri-hydroxylated forms. An RNA-seq analysis identified the upregulation of UFGT, flavonone-3-hydroxylase, and chalcone synthase flavonoid biosynthesis genes in the berry skin of both red variants. The RNA-seq also identified genetic alterations associated with skin color recovery. In red Albariño, VviMybA1 expression was partially recovered and molecular analyses showed that it was due to a partial Gret1 jump. In red Verdejo, RNA-seq alignments indicated the recovery of the reading frame of VviMybA2 likely due to an intra-genic domain replacement. We identified for the first time grape color recovery associated with a regain of VviMybA2 function, which enabled us to determine the specific role of the two major transcription factors regulating grape anthocyanin accumulation.