Shikanai T, Endo T, Hashimoto T, Yamada Y, Asada K, Yokota A
Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, 630-0101 Japan.
Proc Natl Acad Sci U S A. 1998 Aug 4;95(16):9705-9. doi: 10.1073/pnas.95.16.9705.
To evaluate the physiological significance of cyclic electron flow around photosystem (PS) I, we used a reverse genetic approach to focus on 11 chloroplast genes that encode homologs of mitochondrial complex I subunits (ndhA-K). Since their discovery, the exact function of the respiratory components in plant chloroplasts has been a matter of discussion. We disrupted one of these genes (ndhB) in tobacco by chloroplast transformation. Analysis of the transient increase in chlorophyll fluorescence after actinic light illumination and the redox kinetics of P700 (reaction center chlorophylls of PS I) suggest that the cyclic electron flow around PS I is impaired in the ndhB-deficient transformants. Transformants grew normally in a greenhouse, suggesting that the cyclic electron flow around PS I mediated by ndh gene products is dispensable in tobacco under mild environmental conditions.
为了评估围绕光系统（PS）I的循环电子流的生理意义，我们采用反向遗传学方法，聚焦于11个叶绿体基因，这些基因编码线粒体复合体I亚基（ndhA-K）的同源物。自它们被发现以来，植物叶绿体中呼吸成分的确切功能一直是讨论的焦点。我们通过叶绿体转化破坏了烟草中的其中一个基因（ndhB）。对光化光照射后叶绿素荧光的瞬时增加以及P700（PS I的反应中心叶绿素）的氧化还原动力学分析表明，在ndhB缺陷型转化体中，围绕PS I的循环电子流受到损害。转化体在温室中正常生长，这表明在温和环境条件下，由ndh基因产物介导的围绕PS I的循环电子流在烟草中是可有可无的。
