Description of a catalase gene involved in responses to temperature stress.

Catalase (CAT) is an antioxidant enzyme that plays a significant role in cellular protection against oxidative damage by degradation of hydrogen peroxide to oxygen and water. In the present study, the complete CAT cDNA sequence of was identified through expressed sequence tags (EST) analysis and the rapid amplification of cDNA ends (RACE) technique. The nucleotide sequence of CAT cDNA consisted of 1,816 bp with a 1,434 bp open reading frame (ORF), encoding a polypeptide of 477 amino acid residues, which possessed significant homology to other known plant CATs. The molecular mass of the predicted protein was 55.3 kDa with an estimated isoelectric point of 6.40. Phylogenetic analysis showed that CAT was closely related to CAT from gramineous species. In response to temperature stress, HO and MDA contents in increased significantly with cold stress (<10 °C) and heat stress (>25 °C). CAT expression was significantly upregulated at temperatures from 5 to 10 °C and then gradually downregulated, reaching its lowest expression at 30 °C. Recombinant CAT protein exhibited strong antioxidant activity over a wide temperature range, with the highest rCAT activity observed at 25 °C and a higher relative activity retained even with heat stress. All these results indicated that CAT was a member of the plant CAT family and involved in minimizing oxidative damage effects in under temperature stress.