Characterisation, Mrna Expression And Nutritional Regulation Of A Delta 6 Fatty Acyl Desaturase-Like Gene By Dietary Dha Levels Of Perinereis Aibuhitensis (Gube, 1878)

The Delta 6 fatty acyl desaturase (Delta 6 Fad) enzyme plays an important role in the pathways for the biosynthesis of the highly unsaturated fatty acids (HUFA) by converting linoleic (LA, 18:2n-6) and alpha-linolenic (LNA, 18:3n-3) acids to 18:3n-6 and 18:4n-3, respectively. In the present study, a Delta 6 Fad-like gene was cloned and its characterisation, tissue expression and nutritional regulation by dietary DHA (docosahexaenoic acid) levels were analysed in the clamworm Perinereis aibuhitensis. The full-length cDNA was 1535 bp including a 1335 bp open reading frame (ORF) encoding a polypeptide of 444 amino acids, a 113 bp 50'-UTR and an 87 bp 3'-UTR with a poly (A) tail. Sequence comparison revealed that the predicted protein shared higher homologies with Delta 6 Fad from Apostichopus japonicus with 56% identify. The tissue distribution of P. aibuhitensis Delta 6 Fad-like mRNA was found predominantly in intestine, followed by head, esophagus, stomach and other tissues. Quantitative PCR showed that the Delta 6 Fad-like transcriptional levels in intestine gradually decreased with increased content of dietary DHA.