Two conserved Z9-octadecanoic acid desaturases in the red flour beetle, Tribolium castaneum

Z9 Desaturases catalyse the formation of a cis-unsaturated bond in the Δ9 position of the saturated fatty acids stearate and palmitate. They are considered essential enzymes in eukaryotic organisms as their Z9 unsaturated fatty acid products are required for homeostatic roles such as maintenance of membrane fluidity. Two putative Z9 acyl Coenzyme-A desaturase genes were identified in the red flour beetle, Tribolium castaneum, genome (TcasZ9desA and B) based on their similarity to acyl CoA-desaturases of other insects. TcasZ9desA and B share 75% nucleic acid sequence identity and appear to be functionally conserved; the genes were cloned and expressed in the yeast strain Saccharomyces cerevisiae (ole1); both genes complemented the yeast requirement for Z9 fatty acids and produced substantial quantities of Z9 desaturated products with a stearate>palmitate chain length preference. Quantitative PCR analysis of transcripts in RNA obtained from adult, larval and pupal stages of the beetles show TcasZ9desA and B are expressed at similar levels in all stages, with the pupal stage having the lowest expression.