O2 supports 3-phosphoglycerate-dependent O2 evolution in chloroplasts from spinach leaves |
| |
| Authors: | Daisuke Takagi Hiroshi Yamamoto Katsumi Amako Amane Makino Toshio Sugimoto |
| |
| Institution: | 1. Department of Biological and Environmental Science , Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University , 1-1 Rokkodai, Nada, Kobe 657-8501 , Japan;2. Department of Botany , Graduate School of Science, Kyoto University , Sakyo-ku, Kyoto 606-8502 , Japan;3. Faculty of Nutrition , Kobegakuin University , 518 Arise, Iyadani, Nishi, Kobe 651-2180 , Japan;4. Department of Agriculture , Graduate School of Agricultural Science, Tohoku University , Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai 981-8555 , Japan;5. CREST , JST , 7 Gobancho, Chiyoda-ku, Tokyo 102-0076 , Japan |
| |
| Abstract: | We tested the hypothesis that the Mehler-ascorbate peroxidase (MAP) pathway supports 3-phosphoglycerate (PGA)-dependent oxygen (O2) evolution using intact chloroplasts. Lowering O2 concentration (<1?µM) suppressed PGA-dependent O2 evolution rate. High O2 concentration (about 250?µM) enhanced the electron fluxes in Photosystem II (PSII). Also, high O2 concentration oxidized both QA in PSII and Cyt f in thylakoid membranes. These results indicated that the MAP pathway stimulated photosynthetic electron transport. Furthermore, electrochromic shift signal was also increased at high O2 concentration, compared to low O2 concentration. Non-photochemical quenching of chlorophyll fluorescence was also enhanced at high O2 concentration. These data support our hypothesis that the MAP pathway functioned in intact chloroplasts and accelerated PGA-dependent O2 evolution by inducing ΔpH formation to produce and supply adenosine triphosphate (ATP) to the conversion reaction of PGA to glyceraldehyde 3-phosphate through 1,3-diphosphoglycerate in chloroplasts. |
| |
| Keywords: | cyclic electron flow (CEF) Mehler-ascorbate peroxidase (MAP)-pathway O2 3-phosphoglycerate (3-PGA) water-water cycle |
|
|
