高等植物叶绿体中光诱导生成NO的ESR证据

NO分子在生物细胞体系中是一个十分重要的信使分子,它具有调节细胞凋亡、松弛平滑肌、抑制血小板聚集与黏附、抑制病原体和肿瘤生长等多种生理功能^1,2],因而备受生物学家的关注.众所周知,动物细胞中NO主要来源于一氧化氮合酶(NOS)的表达^3];然而,直到最近才有研究证明植物细胞中存在参与调节植物生长和激素信号转导的NOS基因^4].一般认为植物细胞中NO主要来源于硝酸盐还原酶(NR)^5].我们曾在高等植物光系统中研究发现了与电子传递相关的活性氧生成机制^6～8],但其间是否也会通过光诱导电子传递产生NO尚不清楚.Kozlov等^9]曾报道在小鼠线粒体内存在与亚硝酸盐还原酶功能类似的还原型烟酰胺腺嘌呤二核苷酸(NADH)诱导电子传递生成NO的反应,本文采用电子自旋共振(ESR)方法验证了高等植物叶绿体内光诱导电子传递可产生NO的设想.

ESR Evidence on Light-induced Nitric Oxide Formation in Higher Plant Chloroplasts

Spin-trapping ESR method was used to study a novel NO formation pathway in higher plant chloroplasts with Fe 3+ (MGD)_2 as a NO trap. The oxygen evolution complex (OEC) of the chloroplasts was treated with TEMED,and the electron donor DPC was provided to recover the electron transfer chain. Under anaerobic conditions,NO -_2 was reduced by strongly illuminating chloroplast to form NO. However,when kept in dark or when illuminated without DPC,no NO signal could be detected in the reaction system. The results show that the formation of NO is closely related with the light-induced electron transfer in higher plant chloroplasts. WT5HZ]