Tissue-specific Expression Analysis Of Anthocyanin Biosynthetic Genes In Whiteand Red-fleshed Grape Cultivars

Yan73 and Muscat Hamburg(the male parent of Yan73)were used to explore molecular mechanisms of grape berry coloring.We analysed the differential accumulation of anthocyanins in the skin and flesh tissues of two grape varieties based on HPLC-MS analysis,as well as the differential expression of 18 anthocyanin biosynthesis genes in both varieties by quantitative RT-PCR.The results were as follows:(1)18 types of anthocyanins were detected in the skin and flesh of Yan73.The skin and flesh of Yan73 had the similar qualitative profiles of anthocyanins,but different quantitive profiles of anthocyanins.Malvidin-3-O-glucoside and its derivatives were dominant in the skin of Yan73,but in the flesh of Yan73,malvidin-3-O-glucoside and its derivatives were dominant before 74 days after anthesis(DAA)and after 74 DAA,peonidin-3-O-glucoside and its derivatives were dominant.The skin of Yan73 had a higher relative abundance of 3’5’-OH anthocyanins and acylated anthocyanins compared with the flesh throughout the period of anthocyanin synthesis.On the other hand,both the skin and pulp of Yan73 had similar percentages of methoxylated anthocyanins and these percentages were sustained at a high level during all stages of fruit development.Additionally,pelargonidin-3-O-glucoside,which was hardly detected in most other Vitis vinifera berries,was detected in the flesh and skin of Yan73.(2)The flesh of Muscat Hamburg did not contain any detectable anthocyanins and 11 types of anthocyanins were detected in the skin of Muscat Hamburg.Throughout all the stages of fruit development,the total anthocyanin content in the skin of Muscat Hamburg was lower than in the skin of Yan73.Cyanidin-3-O-glucoside and its derivatives were main anthocyanins in the skin of Muscat Hamburg,followed by malvidin-3-O-glucoside and its derivatives.Moreover,the proportions of 3‘5’-OH anthocyanins and acylated anthocyanins in the skin of Muscat Hamburg were lower than those in Yan73 skin.Pelargonidin-3-O-glucoside was not detected in the skin of Muscat Hamburg.(3)Among the 18 genes,the white flesh of Muscat Hamburg showed moderate levels of VvMYB5 a,VvMYB5b,VvMYBPA1,VvMYCA,VvMYC1,VvF3’H and VvWDR1 expression,butthe transcripts of VvGST,VvOMT,VvAM3,VvCHS3,VvUFGT,VvMYBA1,VvF3’5’H,VvF3H1 and VvLDOX were barely detectable in the white flesh of Muscat Hamburg.In particular,VvGST,VvOMT,VvAM3,VvCHS3 and VvF3H1 showed approximately 50-fold downregulation in the white flesh of Muscat Hamburg compared to the red flesh of Yan73.These results suggested that VvGST,VvOMT,VvAM3,VvCHS3,VvUFGT,VvMYBA1,VvF3’5’H,VvF3H1 and VvLDOX were the candidate genes that might show tissue-specific expression.(4)A correlation analysis between the accumulation of different types of anthocyanins and gene expression indicated that the acylated anthocyanins and the 3‘5’-OH anthocyanins were more closely associated with the cumulative expressions of VvGST,VvF3‘5’H,VvLDOX and VvMYBA1,while the total anthocyanins and methoxylated anthocyanins were more closely associated with VvOMT andVvAM3.Therefore,the transcripts of VvOMT,VvAM3,VvGST,VvF3‘5’H,VvLDOX and VvMYBA1 explained most of the variation in the amount and composition of anthocyanins in skin and flesh of Yan73.In conclusion,the data suggest that the specific localization of anthocyanins in the flesh tissue of Yan73 is most likely due to the tissue-specific expression of VvOMT,VvAM3,VvGST,VvF3’5’H,VvLDOX and VvMYBA1 in the flesh.