Yamazaki J Y, Kamimura Y, Nakayama K, Okada M, Sugimura Y
Department of Biology, Faculty of Science, Toho University, Funabashi, Chiba, Japan.
J Photochem Photobiol B. 2000 Mar;55(1):37-42. doi: 10.1016/s1011-1344(00)00022-1.
A novel type of degradation of photosystem I peripheral antenna complexes has been observed in rice leaves under darkness in the present study. Photosynthesis, chlorophyll content, the chlorophyll a/b ratio, and relative amounts of ribulose-1,5-bisphosphate carboxylase/oxygenase decrease during dark treatment. The levels of photosystem II reaction-center complex and cytochrome f on the basis of units of chlorophyll also decline rapidly under darkness. In contrast, the levels of photosystem I reaction-center complex remain stable under darkness for six days. Low-temperature fluorescence emission spectra ascribed to photosystem I antennae clearly show a blue shift. A similar shift is also observed in the photosystem I complexes resolved with dodecyl maltoside-polyacrylamide gel electrophoresis. Moreover, polypeptide analysis of the thylakoids and photosystem I complexes isolated from the green gels shows that some polypeptides originating from photosystem I peripheral antenna complexes disappear during the dark treatment. A curve-fitting method also displays remarkable changes in the chlorophyll components between the light and dark treatments. It is likely that these results indicate the disconnection/disassembly of the photosystem I antenna as well as the photosystem II complexes induced by dark treatment. Moreover, these findings also imply the existence of different degradation mechanisms for the photosystem I and II complexes.
在本研究中，于黑暗条件下的水稻叶片中观察到了一种新型的光系统I外周天线复合体降解现象。在黑暗处理期间，光合作用、叶绿素含量、叶绿素a/b比值以及核酮糖-1,5-二磷酸羧化酶/加氧酶的相对含量均下降。基于叶绿素单位的光系统II反应中心复合体和细胞色素f的水平在黑暗条件下也迅速下降。相比之下，光系统I反应中心复合体的水平在黑暗条件下六天内保持稳定。归属于光系统I天线的低温荧光发射光谱明显显示出蓝移。在用十二烷基麦芽糖苷-聚丙烯酰胺凝胶电泳解析的光系统I复合体中也观察到了类似的位移。此外，从绿色凝胶中分离出的类囊体和光系统I复合体的多肽分析表明，一些源自光系统I外周天线复合体的多肽在黑暗处理期间消失。曲线拟合方法也显示出光照和黑暗处理之间叶绿素成分的显著变化。这些结果可能表明黑暗处理诱导了光系统I天线以及光系统II复合体的断开/解体。此外，这些发现还暗示了光系统I和II复合体存在不同的降解机制。
