Gr39a, a Highly Diversified Gustatory Receptor in Drosophila, has a Role in Sexual Behavior

Abstract

Sexual recognition among individuals is crucial for the reproduction of animals. In Drosophila, like in many other animals, pheromones are suggested to play an important role in conveying information about an individual, such as sex, maturity and mating status. Sex-specific cuticular hydrocarbon components are thought to be major sex pheromones in Drosophila, and are postulated to act through the gustatory system, since they are mostly non-volatile chemicals. However, very little is known about the molecular and neural bases of gustatory pheromone reception. So far, a few putative gustatory receptors, including Gr32a and Gr68a, have been implicated in courtship behavior. Here, we examine another putative gustatory receptor, Gr39a, which shares a cluster with both Gr32a and Gr68a in a molecular phylogeny of the gustatory receptor family, for its potential role in courtship behavior. The Gr39a gene produces four isoforms through alternative splicing of different 5'-most exons. A quantitative real-time PCR analysis showed that the expression levels of all four splice variants of Gr39a were reduced in a fly line in which a P element was inserted into the Gr39a locus. Homozygous and hemizygous males for the P-element insertion, as well as males in which Gr39a was knocked down by RNAi, all showed reduced courtship levels toward females. The courtship levels returned to normal when the P element was excised out. A close analysis of courtship behavior of the mutant males revealed that the average duration of a continuous courtship bout was significantly shorter in the mutants than in the wild type. The results suggest that Gr39a has a role in sustaining courtship behavior in males, possibly through the reception of a stimulating arrestant pheromone.

Drosophila Chemoreceptors: A Molecular Interface Between the Chemical World and the Brain

“…Mutation or knockdown of Gr39a in males led to reduced courtship of females, consistent with the notion that these receptors signal the presence of an excitatory female pheromone [75]. Mutation of Gr32a also led males to court other males and previously mated females, as if this receptor signals the presence of an inhibitory pheromone [76].…”

A Systematic Analysis of Drosophila Gustatory Receptor Gene Expression in Abdominal Neurons which Project to the Central Nervous System

“…Genetic approaches disrupting the activity of Gr68a-expressing neurons, Gr32a, Gr33a, or Gr39a, cause alterations in courtship behavior, consistent with a role in pheromone detection (Bray and Amrein, 2003;Miyamoto and Amrein, 2008;Watanabe et al, 2011). Gr21a and Gr63a together mediate the CO 2 response in the antenna (Jones et al, 2007;Kwon et al, 2007).…”

Chemicals and chemoreceptors: ecologically relevant signals driving behavior in Drosophila

“…GR68a is exclusively expressed in male forelegs (Figure 2A), and its expression depends on the sex determination factor doublesex (Bray and Amrein, 2003). In addition, GR39a may also be involved in female pheromones perception since male mutants for GR39a display reduced courtship toward wild-type females (Watanabe et al, 2011).…”