Molecular characterization, tissue distribution and differential nutritional regulation of putative Elovl5 elongase in silver barb (Puntius gonionotus).

Fatty acid desaturase (Fads) and elongase (Elovl) are two important enzymes involved in the biosynthesis of long-chain polyunsaturated fatty acids (LC-PUFAs) in fishes. Silver barb (Puntius gonionotus) is considered a promising medium carp species for freshwater aquaculture in Asia. Earlier, Δ6 fads cDNA was characterized to understand the molecular mechanism of LC-PUFA biosynthesis in this species. In the present study elovl5-like elongase full-length cDNA was cloned and characterized by RACE (rapid amplification of cDNA ends), and analyzed its basal expression in various organs/tissues by quantitative real time PCR (qRT-PCR) assay. Differential expression of elovl5 cDNA in various tissues following replacement of fish oil (FO) with linseed oil (LO) in the diet also studied. The full length cDNA sequence of silver barb elovl5-like elongase consisted of 1853bp, including an open reading frame (ORF) of 876bp encoding a precursor protein of 291 amino acids possessing the entire characteristic features of Elovl protein. The elovl5 transcript was constitutively expressed in all the tissues examined: muscle, liver, brain, kidney, skin, intestine, gill and eye. The expression of elovl5 gene was upregulated, whereas the serum biochemical constituents were either remain unchanged or lowered following replacement of FO with LO in the diets. We report for the first time, an in silico 3D structure model of elongase protein from silver barb. All these findings may contribute to a better understanding the potential regulatory mechanisms involved and may be useful for enhancing endogenous LC-PUFA production in silver barb.