Plant & Animal Genomes XIII Conference Plant & Animal Genomes XIII ConferenceJanuary 15-19, 2005
Town & Country Convention Center
San Diego, CA
Xiaozhong Zheng , Douglas R. Tocher , Cathryn A. Dickson , J. Gordon Bell , Alan J. Teale
FISH are an important source of the n-3 highly unsaturated fatty acids (HUFA). The synthesis of HUFA involves enzyme-mediated desaturation, and a ∆5 fatty acyl desaturase cDNA has been cloned from Atlantic salmon (Salmo salar) and functionally characterized previously. Here we report cloning and functional characterisation of a ∆6 fatty acyl desaturase of Atlantic salmon, together with its genomic structure, tissue expression and nutritional regulation. A full-length cDNA for a putative fatty acyl desaturase containing 1365 bp encoding 454 amino acid residues was isolated and cloned by polymerase chain reaction (PCR). The protein sequence included the three histidine boxes, two transmembrane regions, and N-terminal cytochrome b5 domain containing the haem-binding motif HPGG that are characteristic of microsomal fatty acid desaturases. Functional expression showed that this gene possessed predominantly ∆6 desaturase activity. Screening and sequence analysis of the genomic DNA of a single fish revealed that the ∆6 desaturase gene comprised 12 exons and spanned 7242 bp of genomic DNA (GenBank accession no. AY736067). Quantitative real time PCR assay of gene expression showed that both ∆6 and ∆5 fatty acyl desaturase genes, and a fatty acyl elongase gene, were highly expressed in intestine, liver and brain, and less so in kidney, heart, gill, adipose tissue, muscle and spleen. Furthermore, expression of both ∆6 and ∆5 fatty acyl desaturase genes in intestine, liver, red muscle and adipose tissue was significantly increased in salmon fed a diet containing vegetable oil compared to in fish fed a diet containing fish oil.