Two Δ6-desaturase-like genes in common carp (Cyprinus carpio var. Jian): Structure characterization, mRNA expression, temperature and nutritional regulation

Delta 6-Desaturase is the rate-limiting enzyme involved in highly unsaturated fatty acid (HUFA) biosynthesis. There is very little information on the evolution and functional characterization of Delta 6Fad-a and Delta 6Fad-b in common carp (Cyprinus carpio var. Jian). In the present study, the genomic sequences and structures of two putative Delta 6-desaturase-like genes in common carp genome were obtained. We investigated the mRNA expression patterns of Delta 6Fad-a and Delta 6Fad-b in tissue, hatching carp embryos, larvae by temperature shock and juveniles under nutritional regulation. Our results showed that the two Delta 6Fad genes had identical coding exon structures, being comprised of 12 coding exons, and with introns of distinct size and sequence composition. They were not allelic variants of a single gene. Both Delta 6Fad genes were highly expressed in liver, intestine (pyloric caeca) and brain. The Delta 6Fad-a and Delta 6Fad-b mRNAs showed an increase in expression from newly hatched to 25 days after hatching. The expression levels of Delta 6Fad-a were obviously regulated by temperature, whereas Delta 6Fad-b was not affected by temperature. The regulation of Delta 6Fad-a and Delta 6Fad-b in response to dietary fatty acid composition was determined in liver, brain and intestine (pyloric caeca) of common carp fed with diets: diet1 with fish oil (FO) rich in n-3 HUFA, diet2 with corn oil (CO, 18:2n-6) and diet3 with linseed oil (LO, 18:3n-3). The differential expression of Delta 6Fad-a and Delta 6Fad-b genes in liver, brain and intestine in common carps was fed with different oil sources, respectively. Further work is in progress to determine the mechanism of differential expression of the Delta 6Fad-a and Delta 6Fad-b genes in different tissues and the roles of transcription factors in regulating HUFA synthesis. (C) 2013 Elsevier B.V. All rights reserved.