title: Quality control of Photosystem II: an FtsH protease plays an essential role in the turnover of the reaction center D1 protein in Synechocystis PCC 6803 under heat stress as well as light stress conditions.
abstract: The role of an AAA protease FtsH (slr0228) in the turnover of the D1 protein was studied under moderate heat stress conditions using wild-type cells of the cyanobacterium Synechocystis PCC 6803 and the mutant cells lacking a homologue of FtsH (slr0228). When the growth temperature of the wild-type was shifted from 30 degrees C to 40 degrees C, growth and oxygen-evolving activity were partially inhibited. Under the same heat stress, growth of the mutant was inhibited more significantly (63% inhibition after 5 days heat stress, compared with 26% inhibition with the wild-type cells) and the oxygen-evolving activity was also impaired in parallel. With heat stress at 42 degrees C, the level of the D1 protein of wild type cells was decreased, whereas that in mutant cells was not. The responses of cyanobacterial cells to heat stress observed here are quite similar to those to light stress that were reported previously. From these results, we suggest that the FtsH protease (slr0228) is responsible for both the heat-induced and light-induced degradation of the D1 protein. Notably, the amount of FtsH increased when the wild-type cells were exposed to heat stress or light stress, indicating that the up-regulation of the FtsH protease in the thylakoids is crucial for the cyanobacterial cells to cope with these abiotic stresses.
authors.affiliation: Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan. yasusiya@cc.okayama-u.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kamata
authors.forename: Hideki
authors.initials: H
authors.lastname: Hiramoto
authors.forename: Noriko
authors.initials: N
authors.lastname: Morita
authors.forename: Jian-Ren
authors.initials: JR
authors.lastname: Shen
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Mann
authors.forename: Yasusi
authors.initials: Y
authors.lastname: Yamamoto
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002452:Cell Count; D006358:Hot Temperature; D008027:Light; D008565:Membrane Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D010100:Oxygen / Q000494:pharmacology; D010447:Peptide Hydrolases / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D046939:Synechocystis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; D045332:Photosystem II Protein Complex; D010447:Peptide Hydrolases; D010100:Oxygen