Cloning and expression of the Δ6 fatty acyl desaturases of Coilia nasus

The full-length cDNA of Δ6 fatty acyl desaturases(FAD6) of Coilia nasus,which was involved in the biosynthesis of highly unsaturated fatty acids(HUFA),was cloned by RT-PCR(reverse transcription polymerase chain reaction) and RACE(rapidamplification of cDNA ends) methods. The results revealed that the FAD6 cDNA was 2 032 bp,including an ORF(open reading frame) of 1 338 bp specified a protein of 445 amino acids,which contained three histidine-rich regions and two putative transmembrane domains. The deduced amino acid sequence shared 75%-79% identity with that in Muraenesox cinereus and Rachycentron canadum,and low similarity of freshwater fish. Actually,it was consistent with the results of phylogenetic analysis. The tissue-specific expressions of FAD6 mRNAs were detected in C. nasus. A high expression was observed in the brain and intestine, while relatively high expression was encountered in muscle and liver,and a weak expression in the heart,kidney and gill.