An updated system for the targeted mutagenesis of the psbDI:psbC operon in Synechocystis sp. PCC 6803: mutations targeting Asp460 in CP43 of Photosystem II reduce oxygen-evolving activity and perturb electron transfer in the quinone-Fe-acceptor complex

Upon exposure of photosynthetic organisms to high light (HL), several HL acclimation responses are triggered. Herein, we identified a novel gene, slr0320, critical for HL acclimation in Synechocystis sp. PCC 6803. The growth rate of the Δslr0320 mutant was similar to wild type (WT) under normal light (NL) but severely declined under HL. Net photosynthesis of the mutant was lower under HL, but maximum photosystem II (PSII) activity was higher under NL and HL. Immunodetection revealed the accumulation and assembly of PSII were similar between WT and the mutant. Chlorophyll fluorescence traces showed the stable fluorescence of the mutant under light was much higher. Kinetics of single flash‐induced chlorophyll fluorescence increase and decay revealed the slower electron transfer from QA to QB in the mutant. These data indicate that, in the Δslr0320 mutant, the number of functional PSIIs was comparable to WT even under HL but the electron transfer between QA and QB was inefficient. Quantitative proteomics and real‐time PCR revealed that expression profiles of psbL, psbH and psbI were significantly altered in the Δslr0320 mutant. Thus, Slr0320 protein plays critical roles in optimizing PSII activity during HL acclimation and is essential for PSII electron transfer from QA to QB.

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An improved system for the targeted mutagenesis of thepsbA2gene inSynechocystissp. PCC 6803: mutation of D1-Glu244 to His impairs electron transfer between QAand QBof Photosystem II

New Zealand Journal of Botany ◽

10.1080/0028825x.2019.1617321 ◽

2019 ◽

Vol 57 (2) ◽

pp. 125-136 ◽

Cited By ~ 8

Author(s):

Jack A. Forsman ◽

Regan T. Winter ◽

Julian J. Eaton-Rye

Keyword(s):

Electron Transfer ◽

Photosystem Ii ◽

Targeted Mutagenesis ◽

Pcc 6803

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Mutational Analysis of the PsbL Protein of Photosystem II in the Cyanobacterium Synechocystis sp. PCC 6803

Zeitschrift für Naturforschung C ◽

10.1515/znc-1993-3-424 ◽

1993 ◽

Vol 48 (3-4) ◽

pp. 267-274 ◽

Cited By ~ 24

Author(s):

P. R . Anbudurai ◽

Himadri B. Pakrasi

Keyword(s):

Photosystem Ii ◽

Mutational Analysis ◽

Higher Plants ◽

Fluorescence Emission ◽

Targeted Mutagenesis ◽

Coding Region ◽

Herbicide Binding ◽

Mutant Cells ◽

Synechocystis Sp ◽

Pcc 6803

The psbL gene is a member of the psbEFLJ gene cluster in the cyanobacterium Synechocystis sp. PCC 6803 and higher plants. psbL, a 4.5 kDa protein encoded by this gene, is a component of the photosystem II complex. The amino acid sequence of this protein indicates that it has a single membrane-spanning a-helical domain. We have used a targeted mutagenesis technique to delete the coding region of the psbL gene in Synechocystis 6803. The resultant mutant strain T345 did not show any PSII-mediated oxygen evolution activity and, as a result, could not grow under photoautotrophic conditions. However, it had normal PSI activity. The chlorophyll to phycobilin ratio in the T345 cells was significantly lower than that in the wild type cells. Fluorescence emission spectra (77 K) of the mutant cells showed the absence of a 695 nm band that usually originates from the PSII complex. Binding assays with radioactive diuron demonstrated that the mutant cells did not have any herbicide binding activity. However, immunostaining experiments showed that both the D 1 (the herbicide binding protein) and the D 2 proteins of the PSII reaction center were present at > 25 % of their normal levels in the thylakoid membranes of the T345 mutant cells. Our data indicate that the PsbL protein is essential for the normal functioning of PSII.

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