Journal Article

Overexpressed Superoxide Dismutase and Catalase Act Synergistically to Protect the Repair of PSII during Photoinhibition in Synechococcus elongatus PCC 7942

Penporn Sae-Tang, Yukako Hihara, Isao Yumoto, Yoshitake Orikasa, Hidetoshi Okuyama and Yoshitaka Nishiyama

in Plant and Cell Physiology

Volume 57, issue 9, pages 1899-1907
Published in print September 2016 | ISSN: 0032-0781
Published online July 2016 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pcw110
Overexpressed Superoxide Dismutase and Catalase Act Synergistically to Protect the Repair of PSII during Photoinhibition in Synechococcus elongatus PCC 7942

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The repair of PSII under strong light is particularly sensitive to reactive oxygen species (ROS), such as the superoxide radical and hydrogen peroxide, and these ROS are efficiently scavenged by superoxide dismutase (SOD) and catalase. In the present study, we generated transformants of the cyanobacterium Synechococcus elongatus PCC 7942 that overexpressed an iron superoxide dismutase (Fe-SOD) from Synechocystis sp. PCC 6803; a highly active catalase (VktA) from Vibrio rumoiensis; and both enzymes together. Then we examined the sensitivity of PSII to photoinhibition in the three strains. In cells that overexpressed either Fe-SOD or VktA, PSII was more tolerant to strong light than it was in wild-type cells. Moreover, in cells that overexpressed both Fe-SOD and VktA, PSII was even more tolerant to strong light. However, the rate of photodamage to PSII, as monitored in the presence of chloramphenicol, was similar in all three transformant strains and in wild-type cells, suggesting that the overexpression of these ROS-scavenging enzymes might not protect PSII from photodamage but might protect the repair of PSII. Under strong light, intracellular levels of ROS fell significantly, and the synthesis de novo of proteins that are required for the repair of PSII, such as the D1 protein, was enhanced. Our observations suggest that overexpressed Fe-SOD and VktA might act synergistically to alleviate the photoinhibition of PSII by reducing intracellular levels of ROS, with resultant protection of the repair of PSII from oxidative inhibition.

Keywords: Catalase; Oxidative stress; Photoinhibition; Photosystem II; Protein synthesis; Superoxide dismutase

Journal Article.  6052 words.  Illustrated.

Subjects: Molecular Biology and Genetics ; Biotechnology ; Biochemistry ; Bioinformatics and Computational Biology ; Molecular and Cell Biology ; Plant Sciences and Forestry ; Plant Physiology

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