Involvement of desat1 gene in the control of Drosophila melanogaster pheromone biosynthesis.
ABSTRACT Cuticular pheromones in Drosophila melanogaster are unsaturated hydrocarbons with at least one double bond in position 7: 7-tricosene and 7-pentacosene in males and 7,11 -heptacosadiene and 7,11 -nonacosadiene in females. We have previously shown that a desaturase gene, desat1, located in chromosome region 87 C could be involved in this process: the Desat1 enzyme preferentially leads to the synthesis of palmitoleic acid, a precursor of omega7 fatty acids and 7-unsaturated hydrocarbons. Therefore, we have searched for P-elements in the 87 region and mapped them. One was found inserted into the first intron of the desat1 gene. Flies heterozygous for this insertion showed a large decrease in the level of 7-unsaturated hydrocarbons, comparable to that observed in flies heterozygous for a deficiency overlapping desat1. Less than 1 % of flies homozygous for this insertion were viable. They were characterized by dramatic pheromone decreases. After excision of the transposon, the pheromone phenotype was reversed in 69% of the lines and the other excision lines had more or less decreased amounts of 7-unsaturated hydrocarbons. All these results implicate desat1 in the synthesis of Drosophila pheromones.
Full-textDOI: · Available from: Claude Wicker-Thomas, Feb 06, 2015
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ABSTRACT: Desaturase genes are essential for biological processes, including lipid metabolism, cell signaling, and membrane fluidity regulation. Insect desaturases are particularly interesting for their role in chemical communication, and potential contribution to speciation, symbioses, and sociality. Here, we describe the acyl-CoA desaturase gene families of 15 insects, with a focus on social Hymenoptera. Phylogenetic reconstruction revealed that the insect desaturases represent an ancient gene family characterized by eight subfamilies that differ strongly in their degree of conservation and frequency of gene gain and loss. Analyses of genomic organization showed that five of these subfamilies are represented in a highly microsyntenic region conserved across holometabolous insect taxa, indicating an ancestral expansion during early insect evolution. In three subfamilies, ants exhibit particularly large expansions of genes. Despite these expansions, however, selection analyses showed that desaturase genes in all insect lineages are predominantly undergoing strong purifying selection. Finally, for three expanded subfamilies, we show that ants exhibit variation in gene expression between species, and more importantly, between sexes and castes within species. This suggests functional differentiation of these genes and a role in the regulation of reproductive division of labor in ants. The dynamic pattern of gene gain and loss of acyl-CoA desaturases in ants may reflect changes in response to ecological diversification and an increased demand for chemical signal variability. This may provide an example of how gene family expansions can contribute to lineage-specific adaptations through structural and regulatory changes acting in concert to produce new adaptive phenotypes. © The Author(s) 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.Molecular Biology and Evolution 11/2014; 32(2). DOI:10.1093/molbev/msu315 · 14.31 Impact Factor
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ABSTRACT: The tempo and mode of evolution of loci with a large effect on adaptation and reproductive isolation will influence the rate of evolutionary divergence and speciation. Desaturase loci are involved in key biochemical changes in long-chain fatty acids. In insects, these have been shown to influence adaptation to starvation or desiccation resistance and in some cases act as important pheromones. The desaturase gene family of Drosophila is known to have evolved by gene duplication and diversification, and at least one locus shows rapid evolution of sex-specific expression variation. Here, we examine the evolution of the gene family in species representing the Drosophila phylogeny. We find that the family includes more loci than have been previously described. Most are represented as single-copy loci, but we also find additional examples of duplications in loci which influence pheromone blends. Most loci show patterns of variation associated with purifying selection, but there are strong signatures of diversifying selection in new duplicates. In the case of a new duplicate of desat1 in the obscura group species, we show that strong selection on the coding sequence is associated with the evolution of sex-specific expression variation. It seems likely that both sexual selection and ecological adaptation have influenced the evolution of this gene family in Drosophila.Molecular Ecology 07/2011; 20(17):3617-30. DOI:10.1111/j.1365-294X.2011.05208.x · 5.84 Impact Factor
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ABSTRACT: The genetics of sexual isolation, behavioral differences between species that prevent mating, is understood poorly. Pheromonal differences between species can influence sexual isolation in many animals and in some cases a single locus can cause large functional changes in pheromonal mating signals. Drosophila cuticular hydrocarbons (CHCs) can function as pheromones and consequently affect mate recognition. In a previous study of the two major CHCs in females that affect mating discrimination between Drosophila simulans and D. sechellia, quantitative trait loci (QTL) were identified on the X and third chromosome, and a few candidate genes were potentially implicated. Here we specifically test candidate genes for CHC biosynthesis and determine the genetic architecture of four additional CHCs that differ in abundance between D. simulans and D. sechellia females. The same QTL, and new ones, were found for additional CHCs. By examining all these CHCs and exploring their covariance, we were able to ascribe putative function to the major QTL. Although desaturases have received considerable attention for their role in CHC biosynthesis, evidence here implies that elongases may be just as important. Sex determination genes do not seem to have a role in this species difference although D. sechellia is sexually dimorphic in CHCs, whereas D. simulans is not. Epistatic interactions, only detected for CHCs limited to D. sechellia, imply that complex interactions among loci may also be having a role in these compounds that affect mating isolation.Heredity 09/2009; 103(5):416-24. DOI:10.1038/hdy.2009.79 · 3.80 Impact Factor