Suppression of male courtship by a Drosophila pheromone receptor

Abstract

In male Drosophila, chemosensory cues control many aspects of social behavior. We found that males with a mutated Gustatory receptor 32a gene (Gr32a) show high courtship toward males and mated females, indicating that GR32a functions as a pheromone receptor for a male inhibitory pheromone. Notably, we discovered that tarsal Gr32a-expressing neurons were essential for courtship suppression and projected to the ventrolateral protocerebrum, implying direct communication of chemosensory neurons with a higher-order brain structure.

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).…”

“…Among the Grs observed to express in neurons apparently innervating the reproductive organs, Gr32a is required for pheromone detection (Miyamoto and Amrein, 2008;Wang et al, 2011), and Gr64c is a member of the putative sugar receptor subfamily . It is as yet unclear whether these Grs act as chemosensors for certain molecules in the reproductive organs, or if they act as sensors for completely different modalities.…”

Same-sex sexual behavior and evolution

“…For example, many Drosophila studies examine genetic mutations that affect pheromone receptors (Box 1). Sex-specific pheromones and their accurate detection are crucial for sex recognition in fruit flies, and alterations in sex-recognition pathways can produce males that court other males, females that court females, or males that switch from same-sex to opposite-sex courtship within minutes [4][5][6][7][8][9][10][11][12][13]. In other words, the mutations cause same-sex sexual behavior.…”

“…In other words, the mutations cause same-sex sexual behavior. However, this behavior often occurs alongside opposite-sex courtship as well, with males mating indiscriminately [8,10,11]. So although they show same-sex sexual behavior, males might not actually be exhibiting a preference for one sex over the other (see Box 1).…”

“…Males that lack functional copies of either gene cannot accurately distinguish the sexes using sex-specific pheromones, and therefore court males as well as females. However, the neural pathways and brain centers that are affected differ markedly between the two types of mutants [10,11].…”