Slr0151 in Synechocystis sp. PCC 6803 is required for efficient repair of photosystem II under high‐light condition

Abstract

Cyanobacteria are ancient photosynthetic prokaryotes that have adapted successfully to adverse environments including high-light irradiation. Although it is known that the repair of photodamaged photosystem II (PSII) in the organisms is a highly regulated process, our knowledge of the molecular components that regulate each step of the process is limited. We have previously identified a hypothetical protein Slr0151 in the membrane fractions of cyanobacterium Synechocystis sp. PCC 6803. Here, we report that Slr0151 is involved in PSII repair of the organism. We generated a mutant strain (Δslr0151) lacking the protein Slr0151 and analyzed its characteristics under normal and high-light conditions. Targeted deletion of slr0151 resulted in decreased PSII activity in Synechocystis. Moreover, the mutant exhibited increased photoinhibition due to impairment of PSII repair under high-light condition. Further analysis using in vivo radioactive labeling and 2-D blue native/sodium dodecylsulfate polyacrylamide gel electrophoresis indicated that the PSII repair cycle was hindered at the levels of D1 synthesis and disassembly and/or assembly of PSII in the mutant. Protein interaction assays demonstrated that Slr0151 interacts with D1 and CP43 proteins. Taken together, these results indicate that Slr0151 plays an important role in regulating PSII repair in the organism under high-light stress condition.

Interplay of SpkG kinase and the Slr0151 protein in the phosphorylation of ferredoxin 5 in Synechocystis sp. strain PCC 6803

“…The Slr0151 protein does not have homology with protein phosphatases. It has been previously assigned to assist in regulation of the D1 de novo synthesis and photosystem II (PSII) disassembly/assembly under high light stress as well as to play an important role in the assembly of photosystem I (PSI) . Our results indicate that Slr0151 has yet another function determining the optimal ratio between phosphorylated and nonphosphorylated forms of Fd5, namely preventing its overphosphorylation.…”

“… who analysed the transcriptomics organization of the entire Synechocystis genome, and was corroborated by Yang et al . at the protein level. We observed that elimination of the SpkG kinase resulted in a significant decrease in the expression of the Slr0151 protein (Fig.…”

A Light Harvesting Complex-Like Protein in Maintenance of Photosynthetic Components in Chlamydomonas

“…To determine whether Msf1 is associated with a thylakoid membrane complex, we analyzed membrane fractions of the wild type (UVM4), the Msf1-GFP strains (Msf1-GFP14 and Msf1-GFP16), and msf1 by 2D bluenative (BN)/SDS-PAGE using a slightly modified protocol (Yang et al, 2014). The UVM4 strain was used in order to increase the expression of the chimeric Msf1-GFP protein.…”

“…Among the mutants with the lowest FII values, msf1was chosen for subsequent characterization. 77K fluorescence emission spectra were measured using a fluorescence spectrophotometer (F-2500; Hitachi) as described (Yang et al, 2014) with slight modifications. An excitation wavelength of 435 nm (5-nm bandwidth) was used to induce chlorophyll fluorescence.…”

“…2D BN/SDS-PAGE of membrane protein complexes was performed according to Yang et al (2014), except that the glass bead lysis method was used for the isolation of membrane proteins according to Göhre et al (2006). After separation in the second dimension, the gel was used for immunoblot analysis as described above.…”