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

Abstract

SUMMARYA 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 1956 bp including an ORF of 765 bp. 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.