Characterization, mRNA expression and nutritional regulation of a Δ6 fatty acyl desaturase-like gene by dietary DHA levels of Perinereis aibuhitensis (Gube, 1878)

The Δ6 fatty acyl desaturase (Δ6 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 α-linolenic (LNA, 18:3n-3) acids to 18:3n-6 and 18:4n-3, respectively. In the present study, a Δ6 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 Δ6 Fad from Apostichopus japonicus with 56% identify. The tissue distribution of P. aibuhitensis Δ6 Fad-like mRNA was found predominantly in intestine, followed by head, esophagus, stomach and other tissues. Quantitative real-time PCR showed that the Δ6 Fad-like transcriptional levels in intestine gradually decreased with increased content of dietary DHA.