Transcriptomic profiling reveals a regulatory network governing volatile compound biosynthesis in Shine Muscat grapes...

Winter berries accumulated more free volatile compounds than summer berries, and C₆ volatile compounds were the main contributors to free volatile compounds. The volatile composition of grapes and wines is important in viticulture, since their aroma is one of the most important determinants of grape fruit quality. The aroma and general quality of grape fruit are influenced by the production of volatile compounds primarily influenced by crop management. In this study, the free and bound volatile compounds were determined using gas chromatography-mass spectrometry (GC-MS), along with the transcriptomic analysis using Shine Muscat grape (Vitis labruscana Baily × V. vinifera L.) of summer and winter berries under two-crop-a-year cultivation in Guangxi. The findings demonstrated that phenols, terpenoids, and alcohols were the main bound volatile compounds in fruits from both seasons, whereas aldehydes, terpenoids, and alcohols were the leading free volatile compounds. Free volatile compound concentrations were substantially higher in winter than summer berries, but bound volatile compound concentrations were much lower. Specifically, the concentrations/constitution of free C₆ volatile compounds showed a significant difference between the two seasons and highly correlated with the transcription of three genes involved in the lipoxygenase (LOX) pathway. Winter berries had a higher concentration of aldehydes, which might be ascribed to the higher expression of VvLOXA (VIT_06s0004g01510) and VvHPL1 (VIT_12s0059g01060) genes, while the higher concentration of alcohols in summer berries might be due to the higher expression of alcohol dehydrogenase (VvADH1, VIT_18s0001g15410). Furthermore, two VvBGLU genes (VIT_05s0077g01150, VIT_01s0011g00760) were supposed to regulate the enzymatic hydrolysis of glycoside-bound compounds in grapes. Three transcription factors including MYB60, MYBA1, and GATA16 were highly correlated with VvADH1, and they might play an important role in grape C₆ alcohol biosynthesis. The findings may help to reveal a transcriptional regulation network of volatile compounds biosynthetic in grapes and to develop efficient cultivation practices.