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A Δ11 desaturase gene genealogy reveals two divergent allelic classes within the European corn borer (Ostrinia nubilalis)

DOI: 10.1186/1471-2148-10-112

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Abstract:

The Δ11 desaturase gene genealogy does not differentiate O. nubilalis pheromone strains. However, we find two distinct clades, separated by 2.9% sequence divergence, that do not sort with pheromone strain, geographic origin, or emergence time. We demonstrate that these clades do not represent gene duplicates, but rather allelic variation at a single gene locus.Analyses of patterns of variation at the Δ11 desaturase gene in ECB suggest that this enzyme does not contribute to reproductive isolation between pheromone strains (E and Z). However, our genealogy reveals two deeply divergent allelic classes. Standing variation at loci that contribute to mate choice phenotypes may permit novel pheromone mating systems to arise in the presence of strong stabilizing selection.The origin of novel sex pheromone signaling systems may play an important role in insect speciation. Insect sex pheromones are volatile compounds or mixtures of such compounds, used in many species for mate location, species recognition, and mate choice [1]. In many moths, females produce species-specific chemical cues, and males exhibit species-specific responses (both physiological and behavioral) that are important in mate finding. Males may also produce pheromones that are used by females in exercising mate choice (e.g., [2]). These chemical cues are often blends of long-chain hydrocarbons with acetate, alcohol, or aldehyde functional groups. Because pheromone biosynthetic pathways have been well characterized [3,4], it is now possible to examine how changes at the level of protein sequence or gene expression affect pheromone phenotype, patterns of mating, and ultimately, the nature and origin of barriers to gene exchange.Pheromone signaling systems are described as "highly canalized" because changes in production or response are opposed by strong selection against novel phenotypes [5,6]. Only if the same genes control signal and response (pleiotropy), or if the genes controlling these traits are tigh

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