A rapid response of beta-amylase to nitric oxide but not gibberellin in wheat seeds during the early stage of germination.

The effects of nitric oxide (NO) and gibberellic acid (GA(3)) on the responses of amylases in wheat (Triticum aestivum L.) seeds (caryopses) were investigated during the first 12 h of germination. GA(3) had no effects on the activities of alpha-amylase (EC 3.2.1.1) or beta-amylase (EC 3.2.1.2), either in intact seeds or embryoless halves within 12 h. In contrast, addition of sodium nitroprusside (SNP), an NO donor, was able to induce a rapid increase in beta-amylase activity without affecting alpha-amylase. Furthermore, the rapid response of beta-amylase to SNP in wheat seeds could be attributed to NO and was approximately dose-dependent. Some other aspects of SNP induction of amylase isozymes were also characterized. Further investigations showed that SNP might play an interesting role in the dissociation of free beta-amylase from small homopolymers or heteropolymers. Furthermore, SNP also directly induced the release of bound beta-amylase from glutenin and its crude enzyme preparation. However, the slight increase in protease also induced by SNP might not be responsible for this action. Interestingly, based on the fact that the rapid response of beta-amylase to NO also existed in seeds of other species, such as barley, soybean, rice and watermelon, it might be a universal event in early seed germination.