Three unsaturated fatty acid biosynthesis-related genes in yellow catfish Pelteobagrus fulvidraco: Molecular characterization, tissue expression and transcriptional regulation by leptin

Three key genes, stearoyl-CoA desaturase-1 (SCD1), Δ6 fatty acyl desaturases (Fads2 (Δ6)) and elongase of very long-chain fatty acid 5 (ELOVL5) were firstly isolated and characterized from yellow catfish, Pelteobagrus fulvidraco. The protein sequence of yellow catfish SCD1 and Fads2 (Δ6) possessed all the characteristics of microsomal fatty acid Fads2 (Δ6), including three histidine boxes, two transmembrane regions and one N-terminal cytochrome b5 domain containing heme-binding motif. The protein sequence of yellow catfish ELOVL5 possessed characteristic features of ELOVL5, including multiple transmembrane regions, endoplasmic reticulum retention signal and a single histidine box. mRNAs of the three genes were expressed in various tissues, but their mRNA levels varied among tissues. Intraperitoneal injection of recombinant human leptin (rb-hLEP) inhibited mRNA expression of SCD1, but not Fads2 (Δ6) and ELOVL5. For the first time, our study cloned SCD1, Fads2 (Δ6) and ELOVL5 genes in Siluriformes and demonstrated their differential expression among tissues, and also differential regulation by leptin, which serves to increase our understanding on their physiological function in fish.