PsaL subunit is required for the formation of photosystem I trimers in the cyanobacterium Synechocystis sp. PCC 6803.

Division of Biology, Kansas State University, Manhattan 66506-4901.
FEBS Letters (Impact Factor: 3.34). 01/1994; 336(2):330-4. DOI: 10.1016/0014-5793(93)80831-E
Source: PubMed

ABSTRACT When membranes of the wild type strain of the cyanobacterium Synechocystis sp. PCC 6803 were solubilized with detergents and fractionated by sucrose-gradient ultracentrifugation, photosystem I could be obtained as trimers and monomers. We could not obtain trimers from the membranes of any mutant strain that lacked PsaL subunit. In contrast, absence of PsaE, PsaD, PsaF, or PsaJ did not completely abolish the ability of photosystem I to form trimers. Furthermore, PsaL is accessible to digestion by thermolysin in the monomers but not in the trimers of photosystem I purified from wild type membranes. Therefore, PsaL is necessary for trimerization of photosystem I and may constitute the trimer-forming domain in the structure of photosystem I.

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    ABSTRACT: Little is known so far about RNA regulators of photosynthesis in plants, algae, or cyanobacteria. The small RNA PsrR1 (formerly SyR1) has been discovered in Synechocystis sp PCC 6803 and appears to be widely conserved within the cyanobacterial phylum. Expression of PsrR1 is induced shortly after a shift from moderate to high-light conditions. Artificial overexpression of PsrR1 led to a bleaching phenotype under moderate light growth conditions. Advanced computational target prediction suggested that several photosynthesis-related mRNAs could be controlled by PsrR1, a finding supported by the results of transcriptome profiling experiments upon pulsed overexpression of this small RNA in Synechocystis sp PCC 6803. We confirmed the interaction between PsrR1 and the ribosome binding regions of the psaL, psaJ, chlN, and cpcA mRNAs by mutational analysis in a heterologous reporter system. Focusing on psaL as a specific target, we show that the psaL mRNA is processed by RNase E only in the presence of PsrR1. Furthermore, we provide evidence for a posttranscriptional regulation of psaL by PsrR1 in the wild type at various environmental conditions and analyzed the consequences of PsrR1-based regulation on photosystem I. In summary, computational and experimental data consistently establish the small RNA PsrR1 as a regulatory factor controlling photosynthetic functions.
    The Plant Cell 09/2014; 26:3661-3679. DOI:10.1105/tpc.114.129767 · 9.58 Impact Factor
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    Soumana Daddy, Jiao Zhan, Saowarath Jantaro, Chenliu He, Qingfang He, Qiang Wang
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    ABSTRACT: Synechocystis sp. PCC 6803 is a model cyanobacterium extensively used to study photosynthesis. Here we reveal a novel high light-inducible carotenoid-binding protein complex (HLCC) in the thylakoid membranes of Synechocystis PCC 6803 cells exposed to high intensity light. Zeaxanthin and myxoxanthophyll accounted for 29.8% and 54.8%, respectively, of the carotenoids bound to the complex. Using Blue-Native PAGE followed by 2D SDS-PAGE and mass spectrometry, we showed that the HLCC consisted of Slr1128, IsiA, PsaD, and HliA/B. We confirmed these findings by SEAD fluorescence cross-linking and anti-PsaD immuno-coprecipitation analyses. The expression of genes encoding the protein components of the HLCC was enhanced by high light illumination and artificial oxidative stress. Deletion of these proteins resulted in impaired state transition and increased sensitivity to oxidative and/or high light stress, as indicated by increased membrane peroxidation. Therefore, the HLCC protects thylakoid membranes from extensive photooxidative damage, likely via a mechanism involving state transition. E xposure to high-intensity light (HL) adversely affects the photosynthetic performance, cell growth, and viability of photosynthetic organisms. The damage is largely attributed to oxygen-dependent destruction of the photosynthetic apparatus and other cellular components 1,2. Oxygenic photosynthetic organisms synthesize stress-associated proteins during exposure to HL. These proteins are often important for the acclimation of cells to HL. A family of HL-inducible genes, called hli or scp genes 3,4
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