Expression analysis of the DkNCED1, DkNCED2 and DkCYP707A1 genes that regulate homeostasis of abscisic acid during the maturation of persimmon fruit.

摘要

To reveal details of the role(s) of abscisic acid (ABA) during ripening and regulation of ABA levels, two 9-cis-epoxycarotenoid dioxygenase genes (DkNCED1 and DkNCED2) and the DkCYP707A1 gene for ABA 8'- hydroxylase, were isolated from unripened persimmons. Expression of DkNCED1 increased at the start of ripening and peaked 20 days before harvest, which was consistent with the accumulation of ABA during ripening in persimmons. Expression of the DkNCED2 gene was high in fruits at the immature stage, then declined continuously throughout ripening. Compared to the DkNCED genes, expression of DkCYP707A1 peaked 145 days after full-bloom (DAFB), then declined. Ethylene release decreased gradually from 65 to 115 DAFB, then peaked at 10 days after harvest. Water-deficit stress enhanced the expression of DkNCED1, but down-regulated transcript levels of DkCYP707A1 in the calyx. Results suggest that endogenous ABA content is modulated by a dynamic balance between ABA biosynthesis and catabolism, which is regulated by expression of the DkNCED1 and DkCYP707A1 genes, respectively, during persimmon development and under drought stress.