Functional Analysis of VvBG1 During Fruit Development and Ripening of Grape

beta-glucosidase (BG) was believed to take part in abscisic acid (ABA) synthesis via hydrolysis of ABA glucose ester to release active ABA during plant growth and development. However, there is no genetic evidence available to indicate the role of genes during fruit ripening. Here, the expression patterns of three genes (VvBG1, VvBG2, and VvBG3) encoding beta-glucosidase were analyzed during grape fruit development, and it was found that beta-glucosidase activity increased in grape fruit in response to various stresses. Furthermore, to verify the function of beta-glucosidase during fruit ripening, heterogeneous expression of the VvBG1 gene in strawberry fruit was validated, and the results showed that the VvBG1 over-expression increased beta-glucosidase and promoted the fruit ripening process in strawberry. In addition, we found that ABA contents increased in the VvBG1 over-expression of strawberry fruit, which induced fruit anthocyanin, soluble solid accumulation, and fruit softening. Moreover, genes related to coloring (CHS, CHI, F3H, and UFGT), softening (PG1, PL1, and EXP1), and aroma (SAAT, and QR) were up-regulated. This work will elucidate the specific roles of VvBGs in the synthesis of ABA and provide some new insights into the ABA-controlled grape ripening mechanism.