Enzymatic activities and gene expression of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase in persimmon fruit

The role of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase in ethylene biosynthesis in persimmon fruit (Diospyros kaki Thunb. cv. Hiratanenashi), both intact and wounded, was characterized. In young intact fruit, ethylene production was detected 2 days after harvest, and peaked at 4 days. Little ACC content was detected at 1 day, rapidly increasing 4 days after harvest, and peaking at 7 days. DK-ACS2 was strongly expressed during almost all periods after it commenced at 3 days, followed by a rapid increase in ACC synthase activity at 4 days and a peak at 5 days. DK-ACO1 mRNA accumulation was initiated at harvest time, dramatically increased at 2 days; as a result, high ACC oxidase activity was detected at the beginning of harvest, and peaked at 3 days. DK-ACO1 mRNA accumulation continued during the subsequent days, whereas ACC oxidase activity decreased to a low level. Wounding treatment induced ethylene biosynthesis and ACC accumulation. The strongest DK-ACS2 expression was induced 1 day after wounding, followed by the highest ACC synthase activity, which paralleled ACC accumulation. Abundant DK-ACO1 mRNA accumulation and high ACC oxidase activity were observed at the initiation of wounding and remained at high levels during the days that followed.