Molecular cloning of glutathione peroxidase gene of Antarctic ice microalga Chlamydomonas sp ICE-L and its expression changes under temperature and salinity stress

A complete open reading frame (ORF) encoding a glutathione peroxidase (ICE-LGPx) was determined from Antarctic Chlamydomonas sp. ICE-L by the molecular biological methods. The transcriptional expression patterns of ICE-LGPx under different salinity and temperature stresses were determined by the real-time polymerase chain reaction, and the activities of ICE-LGPx were assayed under salinity stress as well. The full-length cDNA sequence of ICE-LGPx mRNA was 1956bp including an ORF of 765bp. Molecular structure analysis revealed that ICE-LGPx was a selenium-dependent glutathione peroxidase (Se-GPx) containing a form-2 SECIS (SelenoCysteine Insertion Sequence) element. Phylogenetic analysis showed that ICE-LGPx displayed parallel evolution with those of Volvox carteri, Chlorella variabilis, Micromonas sp. RCC299 and Micromonas pusilla. The expression analysis results indicated that transcription of ICE-LGPx was induced by the changes of the salinity and temperature. The change tendency of enzyme activities was similar to that of ICE-LGPx mRNA level. Time- and dose-dependent effects were observed in the salinity treatments and time-dependent effects were found in the temperature treatments as well. These results suggested that ICE-LGPx might play an important role in the acclimatization of Chlamydomonas sp. ICE-L to salt and low temperature stresses. Furthermore, the results of this investigation may help to clarify the acclimatization and stress response mechanisms of Antarctic ice alga.