Cloning And Molecular Evolution Of Fatty Acid Desaturase And Elongase In Four Teleost Fish In Different Lifestyle

Full-length cDNAs of fatty acid desaturase (FAD) and fatty acid elongase (ELO), which were involved in the biosynthesis of highly unsaturated fatty acids (HUFA), were isolated from grass carp(Ctenopharyngodon idellus), mandarin fish (Siniperca chuatsi), Japanese eel (Anguilla japonica), and orange-spotted grouper (Epinephelus coioides), based on RT-PCR and RACE methods. The open reading frames of four FAD genes encode peptides of 444 and 445 amino acids, along with those from other fish species, are similar and shared at least 67% sequence identity with each other, with most of the sequence variation residing in the N-and C-terminal region of the polypeptide. The deduced amino acid sequences is highly conserved that contains all the characteristics of vertebrateΔ6/Δ5 FAD, including three histidine boxes, two membrane-spaning domains, and one cytochrome b5-like domain with the typical heme-binding motif. The ORFs of four ELO genes encode peptides of 291 and 294 amino acids, along with those from other fish species, are similar and shared at least 65% sequence identity with each other, with most of the sequence variation residing in the C-terminal region of the polypeptide. The deduced amino acid sequences contain all the characteristics of vertebrate ELOVL5, including single histidine box redox centre motif, one canonical ER retention signal and multiple transmembrane regions. The phylogenetic trees based on FAD/ELO ORFs, using four different methods (NJ, MP, ML, BI) show that the consensus trees are similar. The phylogenetic sequence analyses grouped the teleost fish into four distinct clusters with the mainly herbivorous and omnivorous freshwater fish, anadromous fish, catadromous fish, seawater fish and carnivorous freshwater fish. These results will help the following study of the HUFA biosynthesis pathway in teleost fish.