cDNA cloning, characterization and expression analysis of ATP ‐binding cassette transmembrane transporter in Exopalaemon carinicauda

ATP ‐binding cassette ( ABC ) transporters are integral membrane proteins which carry diverse substrates across biological membranes. In this study, we report the cloning of a full‐length, 2468‐bp cDNA sequence encoding a gene of the ABC transporter subfamily G ( ABCG ) from the shrimp Exopalaemon carinicauda ( E. carinicauda ). The deduced protein, Ec ABCG , contains 627 amino acid residues, with a theoretical molecular weight of 69.0  kD a. Phylogenetic analysis showed that Ec ABCG shares the highest identity with the homologs of the shrimp species Litopenaeus vannamei and Fenneropenaeus chinensis , and is also closely related to the insect ABC transporter/white proteins. High‐level mRNA expression of Ec ABCG was detected in the tissue of the hepatopancreas and intestine, using a real‐time quantitative reverse‐transcriptase PCR . The ABC transporter mRNA transcript in the hepatopancreas of E. carinicauda was significantly upregulated after 6 h and after 1 h of exposure to acidic and alkaline conditions respectively. Ec ABCG was also induced in the intestine at 1–24 and 3–48 h after exposure to acidic and alkaline conditions respectively. Upon exposure to sulfamerazine diets (50, 100 and 200 mg kg −1 ) for 3 and 6 h, respectively, the mRNA expression of Ec ABCG was upregulated in the hepatopancreas. Ec ABCG was also induced in the intestine after exposure to 50, 100 and 200 mg kg −1 sulfamerazine diets for 6, 3 and 12 h respectively. These results suggest that the ABCG transporter of E. carinicauda might play a role in coping with pH stress and in exporting xenobiotics.