The expression pattern of β-glucosidase genes (VvBGs) during grape berry maturation and dehydration stress

In order to understand more about the role of β-glucosidase gene expression in modulating ABA level, the expression pattern of three cDNAs (VvBG1, VvBG2 and VvBG3) which encode β-glucosidase in ripening grape berries was analyzed in the presence or absence of dehydration stress. The results show that expression of these three VvBG genes was markedly different. Expression of VvBG1 and VvBG2 increased rapidly from veraison to reach a maximum at harvest or several days immediately before harvest, and coincident with ABA accumulation during berry development and ripening. However, expression of VvBG3 differed from VvBG1 and VvBG2 in that transcript levels declined from the early young fruit stage through veraison after which there was no further change. At 10 days before harvest, dehydration treatment of detached grape berries up-regulated the expression of VvBG1 and enhanced ABA accumulation whereas the expression of VvBG2 was down-regulated, VvBG3 was unaffected by dehydration stress. However, in the leaves, dehydration treatment up-regulated the expression of VvBG1 and stimulated the accumulation of ABA but down-regulated expression of VvBG2 and VvBG3. Based on the results obtained, it is concluded that the expression pattern of the three VvBGs is both temporal and tissue specific. Furthermore, expression of the VvBGs might play a role in the regulation of ABA content during berry ripening and in the response of berries to dehydration stress.