Cloning and characteristics analysis of a chitinase gene from Tetranychus urticae Koch

Chitinases are widely distributed in nature as they are found in many species with different functions including chitin digestion, molting, defense/immunity and pathogenicity. In this study, Tetranychus urticae chitinase gene (TuChi) was first reported from mites using techniques of homological cloning and RACE-PCR. The full length of cDNA sequence was 1 882 bp (GenBank number: JQ041366), containing a 3UTR (untranslated region) of 150 bp, a 5UTR of 52 bp. The ORF (Open Reading Frame) of Tuchi encoding cDNA consisted of 1 620 bp with 539 amino acids residues. Its deduced amino acid composition revealed a calculated molecular weight of 60.7 kua and theoretical PI of 5.99. TuChi protein was composed of N-terminal leading signal peptide, catalytic domain, linker region and C-terminal chitin-binding domain, showing a typical insect chitinase domain structure. Phylogenetic analysis showd that there were high homologies between TuChi and insect chitinase family of Group 1, implicating that TuChi may have an important role during molting stage of T. urticae.