Within-population variability in a moth sex pheromone blend, part 2: selection towards fixation

Astrid T Groot,David G Heckel,Ernesto Villacis-Perez,Peter Kuperus,Gerhard Schöfl,Michiel Van Wijk,Dennis Van Veldhuizen

doi:10.1098/rsos.182050

Abstract

To understand how variation in sexual communication systems evolves, the genetic architecture underlying sexual signals and responses needs to be identified. Especially in animals where mating signals are important for mate recognition, and signals and responses are governed by independently assorting genes, it is difficult to envision how signals and preferences can (co)evolve. Moths are a prime example of such animals. In the noctuid moth Heliothis virescens, we found within-population variation in the female pheromone. In previous selection experiments followed by quantitative trait locus (QTL) analysis and expression analysis of candidate desaturase genes, we developed a model involving a trans-acting repressor of the delta-11-desaturase. In our current study with new selection lines, we fixed the most extreme phenotype and found a single underlying mutation: a premature stop codon in the first coding exon of delta-11-desaturase, which we could trace back to its origin in the laboratory. Interestingly, we found no pleiotropic effects of this knock-out mutation on the male physiological or behavioural response, or on growth or fertility. This finding is in contrast to Drosophila melanogaster, where a single desaturase gene affects both female pheromone production and male behavioural response, but similar to other Lepidoptera where these traits are under independent genetic control. To our knowledge, this is the first time that a single point mutation has been identified that underlies the phenotypic variation in the pheromone signal of a moth.

Highlights

To understand how variation in sexual communication systems evolves, the genetic architecture underlying sexual signals and responses needs to be identified
We found no pleiotropic effects of this knock-out mutation on the male physiological or behavioural response, or on growth or fertility. This finding is in contrast to Drosophila melanogaster, where a single desaturase gene affects both female pheromone production and male behavioural response, but similar to other Lepidoptera where these traits are under independent genetic control
As we found C21 to explain most of the pheromone variance in both backcross family 46 (BC46) and backcross family 35 (BC35), our main candidate gene was delta-11-desaturase located on this chromosome

Summary

Introduction

To understand how variation in sexual communication systems evolves, the genetic architecture underlying sexual signals and responses needs to be identified. This finding is in contrast to Drosophila melanogaster, where a single desaturase gene affects both female pheromone production and male behavioural response, but similar to other Lepidoptera where these traits are under independent genetic control To our knowledge, this is the first time that a single point mutation has been identified that underlies the phenotypic variation in the pheromone signal of a moth. Each encoding the same desaturase enzyme, are expressed in neural and non-neural tissues, and transcript-specific RNAi of desat demonstrated effects on both pheromone emission and perception Such genetic coupling has not been found in moth sexual communication systems [17,18,26,27,28,29,30], which makes it difficult to envision how signals and preferences can (co)evolve. Even though the sex pheromones of more than 1600 moth species have been identified (Pherobase.com), the mechanisms of evolutionary change in pheromone systems are still obscure, because the genetic basis of these changes has been identified in only a few cases [15 –18,20]

Methods

Results

Conclusion