Drosophila melanogaster cuticular pheromones consist of unsaturated hydrocarbons with at least one double bond in position 7: 7 tricosene (T) in males and 7,11 heptacosadiene (HD) in females. However, in many African populations like the Tai strain, females possess low levels of 7,11 HD and high levels of its positional isomer 5,9 HD. We have previously isolated a desaturase gene, desat1, from the Canton-S strain (CS), a 7,11 HD-2-rich morph of D. melanogaster. This desaturase is located in 87C, a locus that has been involved in the difference between 7,11 HD and 5,9 HD morphs. Therefore, we have searched for different desaturase isoforms in both strains. We first cloned desat1 in the Tai strain and report here functional expression of desat1 in CS and Tai. In both strains, the Desat1 enzymes have the same ⌬9 specificity and preferentially use palmitate as a substrate, leading to the synthesis of 7 fatty acids. Also found was a desaturase sequence, named desat2, with a homologous catalytic domain and a markedly different N-terminal domain compared with desat1. In CS genome, it lies 3.8 kb upstream of desat1 and is not transcribed in either sex. In the Tai strain, it is expressed only in females and acts preferentially on myristate, leading to the synthesis of 5 fatty acids. We suggest, therefore, that desat2 might play a control role in the biosynthesis of 5,9 HD hydrocarbons in Tai females and could explain the dienic hydrocarbon polymorphism in D. melanogaster.acyl-Coa desaturase ͉ pheromone biosynthesis U nsaturated fatty acids are structural components of membrane lipids. In animals, fatty acids are desaturated by a membrane-bound enzyme complex involving cytochrome b5, cytochrome b5 reductase, and a desaturase (1-3). Desaturases catalyze the introduction of a double bond into the hydrocarbon chain of a fatty acyl-CoA, at a position determined by the enzyme specificity. A low number of animal desaturases have been both molecularly and functionally characterized by heterologous expression in yeast or in Arabidopsis: ⌬9 and ⌬6 desaturases from rat (4, 5), ⌬6 desaturase from mouse (6), 3, ⌬6, and ⌬5 desaturases from Caenorhabditis elegans (7-9), and ⌬11 and ⌬9 desaturases from the moth Trichoplusia ni (10, 11).In the Drosophila melanogaster subgroup, flies use double bonds in cuticular hydrocarbons among other structural parameters to signal sex or species (12, 13). Males have high levels of monoenes, whereas females are rich in dienes, for example 7-tricosene (7T) and 7,11 heptacosadiene (7,11 HD) in the Canton-S strain (CS) (14).Studies in D. melanogaster strongly suggest that the biosynthesis of male monoenes and female dienes follows the same elongation-decarboxylation mechanism characterized in Musca domestica (15, 16) and shares early steps up to vaccenic acid, a common precursor (refs. 17 and 18; Fig. 1). The involvement of a desaturase with a ⌬9 specificity to introduce the common double bond has also been hypothesized (18). We have previously isolated a CS D. melanogaster desaturase gene, desat1, expre...
Drosophila melanogaster produces sexually dimorphic cuticular pheromones that are a key component of the courtship behavior leading to copulation. These molecules are hydrocarbons, with lengths of 23 and 25 carbons in males (mainly with one double bond) and 27 and 29 carbons in females (mainly with two double bonds). Here, we describe an elongase gene, eloF, with female-biased expression. The 771-bp ORF encodes a 257-aa protein that shows the highest sequence identity with mouse SSC1 elongase (33%). The activity of the cDNA expressed in yeast was elongation of saturated and unsaturated fatty acids up to C30. RNAi knockdown in Drosophila led to a dramatic modification of female hydrocarbons, with decreased C29 dienes and increased C25 dienes accompanied by a modification of several courtship parameters: an increase in copulation latency and a decrease in both copulation attempts and copulation. Feminization of the hydrocarbon profile in males by using targeted expression of the transformer gene resulted in high expression levels of eloF, suggesting that the gene is under the control of the sex-determination hierarchy. There is no expression of eloF in Drosophila simulans, which synthesize only C23 and C25 hydrocarbons. These results strongly support the hypothesis that eloF is a crucial enzyme for female pheromone biosynthesis and courtship behavior in D. melanogaster.
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