Saturday, February 12, 2005

The Scientist :: Mutation and speciation

The Scientist :: Mutation and speciation

Mutation in a single fly gene affects environmental adaptation, leading to reproductive isolation | By Cathy Holding

The path from single mutation to reproductive isolation in speciation may not be immediately obvious, but a technique reported by Anthony Greenberg and coworkers at the University of Chicago in the December 5 Science enables direct visualization of the effect of an alteration in a gene in an otherwise unaltered genetic background. It depends on precise integration of a specific gene into the correct genomic locus, and in this way, the role of a gene mutation in differential adaptation can be precisely observed (Science, 302:1754-1757, December 5, 2003).

Greenberg et al. examined the effect of an inactivating mutation in the Drosophila melanogaster gene desaturase 2, which has a role in pheromone production and hence mating in the fruit fly. In a genomic background of the inactive gene, ds2M, the authors introduced an active form of the gene ds2z precisely into the location of the endogenous gene, by recombination using FLP-FRT technology. They examined cuticular hydrocarbon profiles—the basis of pheromone chemistry—in the active and inactive lines and observed that the active profile was not recapitulated despite integration of active ds2, suggesting involvement of other, previously unrecognized gene systems. The authors also studied the role of the desaturase in cold tolerance and observed that active ds2 decreased cold tolerance and increased starvation tolerance when used to replace the inactive gene.

“Although the role of ds2 in premating isolation remains to be firmly established, we have identified a potential ecological basis for the maintenance of pheromone polymorphism as a result of strong geographical differentiation at the ds2 locus,” conclude the authors.
Links for this article
F. Cohan, “Sexual isolation and speciation in bacteria,” Genetica, 116:359-370, November 2002.
[PubMed Abstract]