Dysfunction of Chloroplast Protease Activity Mitigates pgr5 Phenotype in the Green Algae Chlamydomonas reinhardtii

• Published in: Plants (Basel) Vol. 13; no. 5; p. 606
• Main Authors: Ozawa, Shin-Ichiro, Zhang, Guoxian, Sakamoto, Wataru
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 23.02.2024; MDPI
• Subjects: Algae; Amplitudes; Aquatic plants; Chlamydomonas reinhardtii; chloroplast protease; Chloroplasts; D1 protein; Damage accumulation; FtsH protein; Genotype & phenotype; Light; Mutation; Oxidation; Phenotypes; Photoinhibition; Photooxidation; Photosynthesis; Photosystem I; Photosystem II; Protease; Proteinase; Proteins; Protons; Quality control; Photosystem I; chloroplast protease; photoinhibition; Chlamydomonas reinhardtii
• ISSN: 2223-7747; 2223-7747
• DOI: 10.3390/plants13050606

Researchers have described protection mechanisms against the photoinhibition of photosystems under strong-light stress. Cyclic Electron Flow (CEF) mitigates electron acceptor-side limitation, and thus contributes to Photosystem I (PSI) protection. Chloroplast protease removes damaged protein to assist with protein turn over, which contributes to the quality control of Photosystem II (PSII). The PGR5 protein is involved in PGR5-dependent CEF. The FTSH protein is a chloroplast protease which effectively degrades the damaged PSII reaction center subunit, D1 protein. To investigate how the PSI photoinhibition phenotype in would be affected by adding the mutation, we generated double-mutant via crossing, and its phenotype was characterized in the green algae . The cells underwent high-light incubation as well as low-light incubation after high-light incubation. The time course of Fv/Fm values in showed the same phenotype with . The amplitude of light-induced P700 photo-oxidation absorbance change was measured. The amplitude was maintained at a low value in the control and during high-light incubation, but was continuously decreased in . During the low-light incubation after high-light incubation, amplitude was more rapidly recovered in than . We concluded that the PSI photoinhibition by the mutation is mitigated by an additional mutation, in which plastoquinone pool would be less reduced due to damaged PSII accumulation.