Characterization of a new member of the glutathione peroxidase gene family in Oryza sativa.

A cDNA encoding an Oryza sativa glutathione peroxidase, OsGPX1, was isolated and characterized. OsGPX1 encodes a protein of 168 amino acids with a predicted molecular mass of approximately 18.5 kDa. The protein has 92% identity to a GPX of Zea mays, but only 65% identity to rice PHGPX. The deduced amino acid sequence of OsGPX1 contains two GPX active site domains and one WNF(S/T)KF domain. There is no plastid transit peptide sequence, suggesting that OSGPX1 may function in the cytoplasm. OsGPX1 is located slightly over 85.5 cM from the end of the short-arm of chromosome 4. The OsGPX1 transcripts were abundant only in the leaves of mature plants, and were barely detectable in the leaves of seedlings. However, the transcription of OsGPX1 gene was induced in the seedlings within an hour of exposure to salt stress and was also gradually increased by cold and drought stress. These results indicate that OsGPX1 is a stress-inducible gene of the rice glutathione peroxidase family that protects cells against both metabolic and environmental oxidative stresses.