Oxidation of P700 in Photosystem I Is Essential for the Growth of Cyanobacteria.
The photoinhibition of photosystem I (PSI) is lethal to oxygenic phototrophs. Nevertheless, it is unclear how photodamage occurs or how oxygenic phototrophs prevent it. Here, we provide evidence that keeping P700 (the reaction center chlorophyll in PSI) oxidized protects PSI. Previous studies have suggested that PSI photoinhibition does not occur in the two model cyanobacteria, Synechocystis sp. PCC 6803 and Synechococcus elongatus PCC 7942, when photosynthetic CO2fixation was suppressed under low CO2partial pressure even in mutants deficient in flavodiiron protein (FLV), which mediates alternative electron flow. The lack of FLV in Synechococcus sp. PCC 7002 (S. 7002), however, is linked directly to reduced growth and PSI photodamage under CO2-limiting conditions. Unlike Synechocystis sp. PCC 6803 and S. elongatus PCC 7942, S. 7002 reduced P700 during CO2-limited illumination in the absence of FLV, resulting in decreases in both PSI and photosynthetic activities. Even at normal air CO2concentration, the growth of S. 7002 mutant was retarded relative to that of the wild type. Therefore, P700 oxidation is essential for protecting PSI against photoinhibition. Here, we present various strategies to alleviate PSI photoinhibition in cyanobacteria.
Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Nada-ku, Kobe 657-8501, Japan (G.S., K.S., C.M.); and.|Core Research for Environmental Science and Technology, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan (C.M.).
Ginga
G
Shimakawa
Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Nada-ku, Kobe 657-8501, Japan (G.S., K.S., C.M.); and.|Core Research for Environmental Science and Technology, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan (C.M.).
Keiichiro
K
Shaku
Department of Biological and Environmental Science, Faculty of Agriculture, Graduate School of Agricultural Science, Kobe University, Nada-ku, Kobe 657-8501, Japan (G.S., K.S., C.M.); and cmiyake@hawk.kobe-u.ac.jp.|Core Research for Environmental Science and Technology, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan (C.M.) cmiyake@hawk.kobe-u.ac.jp.
Chikahiro
0000-0002-2426-2377
C
Miyake
D001426:Bacterial Proteins / Q000378:metabolism; D002245:Carbon Dioxide / Q000494:pharmacology; D004579:Electron Transport / Q000187:drug effects; D009154:Mutation / Q000235:genetics; D010084:Oxidation-Reduction / Q000187:drug effects; D010641:Phenotype; D010788:Photosynthesis / Q000187:drug effects; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D046940:Synechococcus / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D046939:Synechocystis / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*
D001426:Bacterial Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D002245:Carbon Dioxide