Effects of Gibberellins and Prohexadione on the Activities of Oryzain andα-Amylase in Rice Seeds

摘要

Oryzains, cysteine proteinases of rice seeds, are induced by GA3in germinating rice seeds Abe et al. (1987)Agric. Biol. Chem. 51: 1509. The effects of GA1, GA3, GA4, GA9, and GA20on the production of oryzain andα-amylase were investigated in embryoless half- and whole-seeds of rice (cv. Nipponbare). When gibberellins (GAs) were incubated with embryoless half-seeds, GA1, GA3and GA4induced oryzain andα-amylase, but GA9, and GA20did not. GA9and GAM induced oryzain andα-amylase production in whole seeds, but this production was inhibited by the simultaneous application of prohexadione, an inhibitor of 2β- and 3β-hydroxylation of GAs. Prohexadione did not inhibit the activities of oryzain andα-amylase induced by GA1. These results suggest that GAs possessing the 3β-hydroxyl group induce activities of oryzain andα-amylase in rice seeds and that GA9and GA20have activity only after they are converted metabolically to active GAs, probably GA4and GA1, respectively. GA1, was more active than GA4in both half seeds and whole seeds incubation. Oryzain andα-amylase activities induced by GA4were significantly inhibited in the presence of 10−4M prohexadione. This suggests that the conversion of GA1, to GA4(13-hydroxylation) might be inhibited at a high dose of prohexadione in w