Bioinformatic analysis of the genomes of the cyanobacteria Synechocystis sp. PCC 6803 and Synechococcus elongatus PCC 7942 for the presence of peroxiredoxins and their transcript regulation under stress

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Abstract
The genomes of the cyanobacteria Synechocystis sp. PCC 6803 and Synechococcus elongatus PCC 7942 encode five and six open reading frames (ORFs), respectively, with similarity to peroxide-detoxifying peroxiredoxins (Prx). In addition to one highly conserved gene each for 2-Cys Prx and 1-Cys Prx, the Synechocystis sp. PCC 6803 genome contains one TypeII Prx and two PrxQ-like ORFs, while Synechococcus elongatus PCC 7942 has four PrxQ-like ORFs. The transcript regulation of all these bioinformatically identified genes was analysed under selected stress conditions, i.e. light limitation and light stress, hydrogen peroxide, methylviologen, salinity, as well as nitrogen- and iron-deficiency. The results on specific time- and stress-dependent regulation of transcript amounts suggest conserved as well as variable functions of these putative Prx-s in antioxidant defence. The results are discussed in the context of evolution and physiological function, particularly in relation to photosynthesis.