Effects of light on the photosynthetic apparatus and a novel type of degradation of the photosystem I peripheral antenna complexes under darkness.
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.
Yamazaki
J Y
JY
Department of Biology, Faculty of Science, Toho University, Funabashi, Chiba, Japan. junya@bio.sci.toho-u.ac.jp
Kamimura
Y
Y
Nakayama
K
K
Okada
M
M
Sugimura
Y
Y
D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D003624:Darkness; D004579:Electron Transport / Q000528:radiation effects; D007700:Kinetics; D008027:Light; D045342:Light-Harvesting Protein Complexes; D012275:Oryza / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology / Q000528:radiation effects*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism* / Q000528:radiation effects; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism; D013997:Time Factors
D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002734:Chlorophyll; C037184:chlorophyll b; D012273:Ribulose-Bisphosphate Carboxylase; D000077194:Chlorophyll A