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Zusammenfassung:
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.
