Development of a molecular marker for an anthocyanin 5-O-Glucosyl transferase homologous gene of Vitis ssp. correlated with anthocyanin 3,5-diglucoside formation in berry skin.

Anthocyanin 5-glucosyltransferase (5-GT) is catalyzing the formation of anthocyanin 3-glucosides to anthocyanin 3,5-diglucosides. Following a candidate gene approach, five genes with 37-54% homology to 5-GT genes were isolated from grapevine ‘Regent’. The expression pattern of theses five genes was investigated in berry skin of various genotypes, either with or without the ability to form anthocyanin diglucosides, using 3’-RACE technique. For one gene, which showed a clear correlation of gene activity and anthocyanin diglucoside formation, five corresponding BAC clones were isolated. The analysis of the coding sequence and southern blot experiment revealed that the two very similar sequences found are most probably alleles. The most striking difference between the two alleles is that one allele carries a mutation leading to a frame shift in the coding region. A molecular marker was developed which was used to differentiate both alleles in a ‘Regent’ x ‘Lemberger’ population segregating for the dominant trait ‘anthocyanin diglucosides’. A high correlation was found between the full length 5-GT allele to ‘diglucosides’ and the truncated allele to ‘no diglucosides’, respectively. Thus, it is tempting to speculate that the truncated 5-GT is responsible for the lack of anthocyanin diglucosides in certain Vitis species/ genotypes.