During the course of mungbean ( Phaseolus radiatus L.) germination, the rate of ethylene production and the activity of ACC synthase (1 aminocyclopropane 1 carboxylic acid synthase, EC4.4.1.4) began to increase in the 5th day of germination, and reached its peak in the 10th day and then decreased. The ethylene production and the activity of ACC synthase were obviously promoted by 10 μmol/L exogenous IAA (indole 3 acetic acid).The production of superoxide radical (O[SX(B-*3]-·)]2) and hydrogen peroxide (H2O2) were also promoted by exogenous IAA, suggesting that there was some relationship between active oxygen production and the activity of ACC synthase induced by exogenous IAA. The production of ethylene and the activity of ACC synthase increased dramatically when the seedlings were treated with exogenous O[SX(B-*3]- ·[SX)]2, whereas the exogenous H2O2 had no effects on the production of ethylene and the activity of ACC synthase. Exogenous SOD (superoxide dismutase, one scavenger of O[SX(B-*3]-·[SX)]2) could inhibit the production of ethylene and the activity of ACC synthase, but exogenous CAT (catalase) could not. So it was possible that IAA would stimulate the activity of ACC synthase by inducing the production of O[SX(B-*3]- ·[SX)]2 in germinating mungbean seedlings, and this might be one of the regulating mechanism of ethylene synthesis in higher plants; the production of H2O2 induced by IAA was not the cause of the increase of the activity of ACC synthase and the production of ethylene.
活性氧对外源IAA诱导的ACC合酶活性的影响
柯德森1 王爱国1 孙谷畴1 董良峰2
（1. 中国科学院华南植物研究所，广州510650；2.Department of Biological Sciences,Unixersity of Essex, Colchester CO4 3SQ, UK
摘要： 本文试图从活性氧的角度阐明外源IAA诱导ACC合酶活性的机制.绿豆(Phaseolus radiatus L.)幼苗的乙烯产生及ACC合酶活性从萌发的第5天开始上升,到第10天达到高峰,接着下降.10 μmol/L的外源IAA能明显促进绿豆幼苗乙烯的产生及ACC合酶的活性,同时也促进了超氧阴离子自由基(O2-)、过氧化氢(H2O 2)的产生.显示外源IAA诱导的ACC合酶的活性与其诱导的活性氧的产生具有某种相关性.外源O2-)处理能明显提高绿豆幼苗的乙烯产生速率及ACC合酶的活性,而外源H2O2无论对乙烯产生或ACC合酶的活性均没有明显的作用.外加(O2-)的清除剂SOD对绿豆幼苗乙烯的产生及ACC合酶活性的提高有一定的抑制作用,而外源过氧化氢酶却没有明显的作用.为此我们可以得出结论:外源IAA诱导的绿豆幼苗ACC合酶活性的提高可能是由于其诱导的O(O2-)产生的升高引起的,这可能也是高等植物中调控乙烯生物合成的机制之一;而IAA诱导的H2O2产率的升高并不是其诱导ACC合酶活性升高的原因.
关键词： ACC合酶；乙烯；活性氧；IAA
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