Desaturases Drosophila

Dallerac R., Labeur C., Jallon J.-M, Knipple D. C., Roelofs W. L. and Wicker-Thomas, C. (2000) A A9 desaturase gene with a different substrate specificity is responsible for the cuticular diene hydrocarbon polymorphism in Drosophila melanogaster. Proc. 

Wicker-Thomas C., Henriet C. and Dallerac R. (1997) Partial characterization of a fatty acid desaturase gene in Drosophila melanogaster. Insect Biochem. Molec. Biol. 27, 963-972. 

Females of most Drosophila populations have high amounts of 7,11-FID, while those of African and Caribbean populations have high amounts of 5,9-HD (Jallon and P6chin6, 1989). This difference in hydrocarbons has been mapped to a single locus, 87C-D, which is close to the location of desatl gene (Coyne et al., 1999). This is due to the second desaturase gene, desatl, being located close to desatl. 

After the first three molecular characterizations of animal desaturases from rat liver (Thiede et al., 1986), mouse adipose tissue (Ntambi et al., 1988) and carp (Tiku et al., 1996), a Drosophila desaturase was isolated in 1997 (Wicker-Thomas et al., 1997). Since then, numerous studies have been made on lepidopteran desaturases involved in nonhydrocarbon short-chain pheromones (Knipple et al., 1998 reviewed in Knipple and Roelofs, 2003). In Drosophila, there are seven fatty acyl-CoA desaturase genes, which are all located on chromosome III (Figure 4.1), but only three desaturases appear to be involved in hydrocarbon synthesis. In the cricket, a desaturase has been characterized but there is no evidence that this desaturase is involved in pheromone biosynthesis (Riddervold et al., 2002). On the other hand, the desaturase isolated from the housefly is probably involved in both lipid and pheromone biosynthesis (Eigenheer et al., 2002). 

Can a general pathway be drawn for HC synthesis in Drosophila In mature D. mela-nogaster, only three desaturases seem to participate in pheromone biosynthesis, but as reported in the previous paragraphs, at least four elongases are involved (in cytological positions 55, 68, 85). 

Figure 4.7 Phylogenetic tree of Drosophila, principal pheromones of the species and desaturases involved in their synthesis, (http //flybase.bio.indiana.edu/).

In the melanogaster subgroup, the same enzyme Desatl seems to be involved in the first desaturation step of pheromone synthesis (Figure 4.7), even if the specificity concerning the desaturation is somewhat modified (for example, in D. erecta, stearic acid is used for the first desaturation, instead of palmitic acid as in other species). In other Drosophila species, other enzymes could be involved Desat2 in D. ananassae and another yet unknown desaturase in D. virilis. The position of the double bond on carbon 11 in the latter species could indicate either that the desaturase acts on C20 saturated fatty acid, or that it has another unknown specificity, resembling the unusual specificities of some lepidopteran desaturases. 

Chertemps, T., Duportets, L., Labeur, C., Ueyama, M. and Wicker-Thomas, C. (2006). A female-specific desaturase gene responsible for diene hydrocarbon biosynthesis and courtship behaviour in Drosophila melanogaster. Insect Mol. Biol., 15,465—473. Chertemps, T., Duportets, L., Labeur, C. and Wicker-Thomas, C. (2005). A new elongase selectively expressed in Drosophila male reproductive system. Biochem. Biophys. Res. Commun., 333,1066-1072. 

Coyne, J. A. and Elwyn, S. (2006). Does the desaturase-2 locus in Drosophila melanogaster cause adaptation and sexual isolation Evolution, 60, 279-291. 

Fang, S., Takahashi, A. and Wu, C. (2002). A mutation in the promoter of desaturase 2 is correlated with sexual isolation between Drosophila behavioral races. Genetics, 162, 781-784. 

A female-specific desaturase gene responsible for diene hydrocarbon biosynthesis and courtship behaviour in Drosophila melanogaster. Insect Mol. Biol., 15,465 473. 

Legendre, A., Miao, X.-X., Da Lage, J.-L. and Wicker-Thomas, C. (2008). Evolution of a desaturase involved in female pheromonal cuticular hydrocarbon biosynthesis and courtship behavior in Drosophila. Insect Biochem. Mol. Biol., 38, 244-253. 

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