Transcription and enzymatic analysis of beta-glucosidase VvBG1 in grape berry ripening

摘要

Although beta-glucosidase was recently demonstrated to be involved at transcriptional level in fleshy fruit development, it remains unclear whether BG possesses biochemical activity. In the present study, real-time reverse transcription polymerase chain reaction analysis showed that the mRNA expression levels of beta-glucosidase gene VvBG1 increased rapidly concomitant with berry red-colouring in Muscat Hamburg grapevine (Vitis vinifera), suggesting that the VvBG1 gene might be involved in the berry ripening. In order to explore VvBG1 biochemical activity, a 60-kD recombinant protein, VvBG1, was expressed in Escherichia coli BL21 (DE3) and purified. The results gained from a combination of VvBG1-pulp-homogeneity-incubation test and gas chromatography-mass spectroscopy analysis showed that VvBG1-treated berry samples contained more free ABA than the control, demonstrating that VvBG1 has high glycosyl hydrolase activity that can transform the ABA-glucosyl ester to free ABA. In conclusion, both the high expression and increased hydrolase activity of VvBG1 could suggest an important role of ABA in grape berry ripening.