Cloning and characterization of tryptophan 2,3-dioxygenase gene of Zhikong scallop Chlamys farreri (Jones and Preston 1904)

Abstract

A Zhikong scallop (Chlamys farreri Jones and Preston 1904) tryptophan 2,3-dioxygenase (TDO) gene fragment, down-regulated by Vibrio anguillarum challenge, was isolated using mRNA differential display in our previous work. In this paper, the full-length TDO gene was cloned by 5′-RACE. Chlamys farreri TDO gene consists of 1292 nucleotides encoding an expected polypeptide of 383 amino acids with an estimated molecular weight of 44.8 kDa and an isoelectric point of 6.35. The deduced amino acid sequence is 54–61% homologous to TDOs from Caenorhabditis elegans, Mus musculus, Danio rerio, Homo sapiens and Drosophila melanogaster, and shares several histidine residues important for the enzyme function in other species. Chlamys farreri TDO is expressed in the mantle, gill, digestive gland, testis, adductor muscle and kidney. Immunohistochemical analysis showed that C. farreri TDO was located mainly in the cytoplasm of most cell types. The non-specific distribution of C. farreri TDO suggests that it is involved in various cellular processes.