A homozygous <Emphasis Type="Italic">recA</Emphasis> mutant of <Emphasis Type="Italic">Synechocystis</Emphasis> PCC6803: construction strategy and characteristics eliciting a novel RecA independent UVC resistance in dark |
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Authors: | Renu?Minda Jyoti?Ramchandani Vasudha?P?Joshi Email author" target="_blank">Swapan?Kumar?BhattacharjeeEmail author |
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Institution: | (1) Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai, 400085, India;(2) School of Life Sciences, Devi Ahilya University, Khandwa Road, Indore, 452 017, India |
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Abstract: | We report here the construction of a homozygous recA460::cam insertion mutant of Synechocystis sp. PCC 6803 that may be useful for plant molecular genetics by providing a plant like host free of interference from homologous
recombination. The homozygous recA460::cam mutant is highly sensitive to UVC under both photoreactivating and nonphotoreactivating conditions compared to the wild type
(WT). The liquid culture of the mutant growing in ~800 lx accumulates nonviable cells to the tune of 86% as estimated by colony
counts on plates incubated at the same temperature and light intensity. The generation time of recA mutant in standard light intensity (2,500 lx) increases to 50 h compared to 28 h in lower light intensity (~800 lx) that
was used for selection, thus explaining the earlier failures to obtain a homozygous recA mutant. The WT, in contrast, grows at faster rate (23 h generation time) in standard light intensity compared to that at
~800 lx (26 h). The Synechocystis RecA protein supports homologous recombination during conjugation in recA
— mutant of Escherichia coli, but not the SOS response as measured by UV sensitivity. It is suggested that using this homozygous recA460::cam mutant, investigations can now be extended to dissect the network of DNA repair pathways involved in housekeeping activities
that may be more active in cyanobacteria than in heterotrophs. Using this mutant for the first time we provide a genetic evidence
of a mechanism independent of RecA that causes enhanced UVC resistance on light to dark transition. |
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Keywords: | RecA Cyanobacteria UV sensitivity Photo-regulation DNA repair |
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