The Differences Of Flavonoids Metabolism In 'Cabernet Sauvignon' Grapes From East And West China And The Effect Of Canopy Management On Flavan-3-ol Metabolism

Flavonoids metabolism have been studied widely because of their great contribution to the organoleptic qualities of grapes and wines.The major classes of flavonoid compounds found in grape berries include flavonols,flavan-3-ols(proanthocyanidins)and anthocyanins.Generally,the phenolics biosynthesis in grape skins is sensitive to environmental factors.Many researches reported that light could up-regulate the genes expression related to flavonol and anthocyanin metabolism,and significantly increased the contents of flavonols.While there are several opinions about the effect of light on flavan-3-ols.In the present study,we compared the transcriptional profiles and metabolite profiles of flavonoid pathway during development of 'Cabernet Sauvignon' berries from Changli and Gaotai by RNA-seq and HPLC-MS.After comparison of the differences of flavonoid metabolism between the two regions,we choose one of the most important environment factors for flavonoid metabolism,light,to go on our further study.A series of canopy manipulation were performed on Vitis vinifera L.Cabernet Sauvignon during berry development to study the effect of light on the biosynthesis and accumulation flavan-3-ols.The results were shown as follows:The study was conducted on transcriptional regulation and metabolite profiles of flavonoid pathway of'Cabernet Sauvignon' berries at the stages of pea size,veraison and ripening,corresponding to EL 31,35 and 38.It seemed possible that the combination of climatic differences between the two regions might be one of the significant contributors to the region-specific metabolism pattern.The environment characteristics in Gaotai could well have induced the accumulation of higher levels of flavonols and anthocyanins,and stimulated the flow of more carbon to the F3'5'H branch pathway thereby indirectly reducing the synthesis of flavan-3-ols.We compared the impact of Modified VSP(M-VSP),Fan training with two/multiple trunks(F-TT/F-MT)on the transcriptional and metaboilic level of flavan-3-ols in 'Cabernet Sauvignon' from Xinjiang,China.The results indicated that the expression levels of ANR,LAR1 and MYBPA1 were higher in M-VSP trained berries than the other two training systems.The contents of C,EC,EGC,ECG and total flavan-3-ols were higher in M-VSP accordingly.Moreover,more proportion of tri-hydroxylated flavan-3-ols presented in F-TT and F-MT berries,the mean degree of polymerisation(mDP)was higher in M-VSP berries.Leaf removal was conducted around the bunch zone at the stages of berry set,verasion and post-verasion.The objective of this study was to investigate the effects of bunch exposure on the biosynthesis of flavan-3-ol.The results exhibited that early leaf removal increased the gene expression of enzymes and transcription factors related to biosynthesis of flavan-3-ol as well as the level of flavan-3-ols.While the flavan-3-ols content and concentration decreased during ripening,and the decrease level was higher in early leaf removal berries than that in the control berries.Thus,lower level of flavan-3-ols was observed in the early leaf removal berries at harvest.Tri-hydroxylated flavan-3-ols presented higher levels in all of the leaf removal treatments as well as mDP levels.Aiming to further study the impact of sunlight on the biosynthesis of flavan-3-ol,we shaded the clusters during different stages of berry development with bags which can eliminate light totally.The results shown that sunlight exclusion can affect the flavan-3-ol biosynthesis not only due to the direct effect of light on the expression of genes related to flavan-3-ol metabolic,but also to the effect of light on berry development which may affect flavan-3-ol biosynthesis indirectly.This study provides an additional insight to the environmental effects on flavan-3-ols metabolism in wine grapes.It also provides reliable theoretical foundations to cultivation and management during viticulture process.Moreover,it will serve as an useful reference for future investigations including the exploration of the environmental factors that regulate secondary metabolism on the levels of transcription and metabolite in grape berries.