Gene structure and cDNA sequence of 2-Cys peroxiredoxin in the harmful algal bloom species <i>Chattonella marina</i> and its gene transcription under different light intensities

<p>We investigated the gene structure and predicted amino acid sequence of the antioxidant enzyme 2-Cys peroxiredoxin (2-Cys Prx) in the raphidophyte <i>Chattonella marina</i>, which is a harmful algal bloom (HAB) species. The open reading frame of 2-Cys Prx was 585 bp long and encoded a protein consisting of 195 amino acids. The putative amino acid sequence contained two cysteine residues located at the 49th and 170th amino acid positions from the N-terminal methionine residue. The sequence also possessed 2-Cys Prx characteristic motifs, F (FFYPLDFTFVCPTEI) and EVCP. The position of the 2-Cys Prx gene relative to several others (<i>ycf</i>59 <i>– 2-CysPrx – rpl</i>35 <i>– rpl</i>20) was the same as that found in the chloroplast genome in the raphidophyte <i>Heterosigma akashiwo</i>. Upstream of the 2-Cys Prx gene, possible TATA and GGA motifs recognized by nuclear-encoded plastid RNA polymerase (NEP), and a possible -10 box and -35 box recognized by plastid-encoded plastid RNA polymerase (PEP) were observed. We measured the transcript levels of 2-Cys Prx in <i>C. marina</i> cells grown under three different light intensities (0, 100, 1000 µmol photons m^–2 s^–1, 14-h light/8-h dark photoperiod) by quantitative PCR. The 2-Cys Prx transcript level in cells grown under the highest light intensity on day 3 was threefold that on day 0 but two lower light intensities resulted in relatively stable transcription levels. The 2-Cys Prx transcript level was significantly positively related to the H₂O₂ concentration per cell and the H₂O₂ scavenging activity per cell. These results suggest that <i>C. marina</i> 2-Cys Prx functions in the chloroplast and its transcription could be regulated by both NEP and PEP. Moreover, the 2-Cys Prx transcript level might increase to remove excessive H₂O₂ produced under strong light conditions in order to maintain cell proliferation activity.</p