Abstract:  Catalase (CAT), one of most important enzymes in organism, plays an essential role in active oxygen metabolism and preventing the formation of free hydroxyl radicals by clearing hydrogen peroxide, superoxide radical and peroxides. In this study, the full-length cDNA of CAT gene from the beet armyworm, Spodoptera exigua, was cloned and characterized by RT-PCR and RACE technique, which is 1 755 bp in length and named as SexiCAT (GenBank accession no. JN051294). The open reading frame (ORF) of SexiCAT is 1 524 bp encoding 507 amino acid residues. The amino acid sequence of SexiCAT shares a significant identity with catelases of Bombyx mori (87%), Drosophila melanogaster (73%), Aedes aegypti (71%), and Tribolium castaneum (70%). The temporal expression profiling revealed that SexiCAT was expressed in different developmental stages of S. exigua at different expression levels, with the highest level in adults, the second highest level in larvae and the lowest level in eggs, and the expression level in adults was 7 times as high as that in eggs. Tissue expression profiling further indicated that in 5th instar larvae of of S. exigua SexiCAT transcript was observed in the integument, midgut, fat body and Malpighian tubules, with the highest expression level in fat body. This study provides a foundation for understanding the functions and applications of CAT as a new target for oxidase blocking agent.

Key words:  Spodoptera litura, catalase (CAT), gene cloning, sequence analysis, homology modeling, expression profile