Molecular cloning and nutritional regulation of putative∆6 desaturase mRNA from striped catfish (Pangasianodon hypophthalmus)

Abstract

Here we report the full-length cDNA cloning and nutritional regulation of a putative Δ6 fatty acyl desaturase (Δ6 fads) gene from striped catfish, Pangasianodon hypophthalmus. The 5′ and 3′ RACE analysis revealed a cDNA sequence of 1896 base pairs (bp) comprising a 5′ UTR of 49 bp, 3′ UTR of 509 bp and an open reading frame (ORF) of 1338 bp specifying a protein of 445 amino acids. Bioinformatics analysis showed that the deduced peptide sequence included all the characteristic features of microsomal fatty acyl desaturases, including N-terminal cytochrome b5 domain containing the haem binding motif H-P-G-G, fatty acyl (FA) desaturase domain, three histidine boxes and transmembrane regions. P. hypophthalmus ∆6 desaturase peptide sequence shares high similarity with Pangasius larnaudii (95%) and Clarias macrocephalus (90%). The predicted secondary and tertiary protein structures revealed that desaturase protein contains mostly α-helix followed by random coils and strands. Tissue distribution analysis showed that Δ6 fads is mainly expressed in brain followed by liver, heart, gill and muscle. Since α-linolenic acid is a substrate for the Δ6 FADS enzyme, various concentrations of this fatty acid (0.5, 1, 1.5 and 2 g kg− 1) were administered to experimental fish through feed to find out its effect on the expression of Δ6 fads. Results showed that the liver Δ6 fads gene expression is up-regulated in fish fed with experimental diets (p < 0.05).