What does the fruitless gene tell us about nature vs. nurture in the sex life of Drosophila?

Abstract

The fruitless (fru) gene in Drosophila has been proposed to play a master regulator role in the formation of neural circuitries for male courtship behavior, which is typically considered to be an innate behavior composed of a fixed action pattern as generated by the central pattern generator. However, recent studies have shed light on experience-dependent changes and sensory-input-guided plasticity in courtship behavior. For example, enhanced male-male courtship, a fru mutant "hallmark," disappears when fru-mutant males are raised in isolation. The fact that neural fru expression is induced by neural activities in the adult invites the supposition that Fru as a chromatin regulator mediates experience-dependent epigenetic modification, which underlies the neural and behavioral plasticity.

Keywords: Or47b; behavioral plasticity; courtship; fruitless; olfaction; vision.

Figure 1.

fru-dependent behavioral and physiological plasticities. (A) Development of a behavioral phenotype via social experience in fru mutants. (B and C) When kept in a group, fru^sat males exhibit courtship chaining under freely moving conditions (B), or courtship-like pursuit under tethered conditions in response to a moving visual target displayed on a computer screen (C). The inset in (C) shows the visual pattern used as a target. Arrows indicate the wing extended to vibrate for song generation. (D) Quantification of courtship following activities directed toward an artificial visual target in wild-type and fru^sat males. (E) Ca²⁺ activities recorded from dsx-expressing neurons in the lateral protocerebrum during the presentation of an artificial visual target. The background shading indicates the period during which the target was displayed on the screen. “G” and “S” in (D) and (E) denote that males were reared in a group of 10 individuals and in isolation for 6–9 d after eclosion, respectively. Panels (D) and (E) were reproduced, with permission, from ref..

Figure 2.

Plastic changes in the structure and function of male courtship-circuitry components in the adult stage.