Voila, a new Drosophila courtship variant that affects the nervous system: behavioral, neural, and genetic characterization

Abstract

In Drosophila melanogaster, a specific PGAL4 transposon induces the Voila1 genetic variant and produces multiple phenotypes. Homozygous Voila1/1 flies rarely reach adulthood, whereas heterozygous Voila1/+ adult males show strong bisexual behavior. Males with a single copy of Voila1 driving the feminizing transgene UAS-transformer show very reduced sexual activity but no overall effect on their behavior. Voila1 is specifically expressed in the nervous system. In the CNS, it is expressed mainly in the mushroom bodies and, to a lesser extent, in the antennal lobes. In the peripheral nervous system, GAL4 expression is almost entirely restricted to the gustatory sensilla. Using chromosomal deficiencies, the behavioral alteration was genetically mapped to the same location as the PGAL4 element (86E1-2). The multiple behavioral effects of the Voila genetic variant are discussed in light of its expression in the nervous system and its genetic basis.

Fig. 1.

Courtship behavior ofVoila¹,Voila¹ UAS-tra, and control males. The courtship directed toward intact and decapitated male or female targets is expressed as the courtship index (A) or as the frequency of complete courtship (B). For each genotype, the courtship of 35 and 20 males was measured with male and female targets, respectively. For description of genotypes, see Material and Methods. A, Courtship index values were measured as the percentage of time spent courting by the subject male, during a 10 min observation period. The height of each bar indicates the mean (±SE) for the corresponding genotype. B, The frequency of complete courtship was calculated from the percentage of subject males that attempted copulation with an object fly.

Fig. 2.

Mapping ofVoila¹. A, In situ chromosomal mapping of the PGAL4 insertion in salivary gland of w;Voila¹/+ larva. B, Deficiencies used to map the bisexual courtship observed inVoila¹/TM3 males. Deficiencies are aligned with the salivary gland chromosome map (Lindsley and Zimm, 1992). Bars represent the extent of the deficiencies, and the hatched region represents uncertainty as to breakpoint position. The double-arrowed line indicates the chromosomal region 86D₄–E₁₉. C, Deficiency mapping of the behavioral phenotype ofVoila¹/TM3. Courtship responses of w; Df(3R)/TM3 males toward decapitated male or female targets were measured. The height of each bar indicates the mean (±SE) courtship index measured in at least 25 individuals per genotype (15 for w; +/TM3). All deficiencies were tested over the TM3, Sb Ser balancer chromosome from theVoila¹/TM3 strain. Sexual discrimination (difference between the intensity of homo- and heterosexual courtship) was statistically tested (two-factor ANOVA, Newman–Keuls test) for each genotype. ***p < 0.001. ns, Not significant.

Fig. 3.

Expression ofVoila¹ in the adult nervous system of 4-d-old flies. A, Head cuticle with a complete proboscis. B, Frontal section (10 μm) of the brain.C, Anterior wing margin. D, Frontal view of a whole brain. Expression of the β-galactosidase inVoila¹-UAS-lacZ males (A, C, D). Anti-tau labeling onVoila¹ UAS-tau male (B). The main peripheral nervous structures (shown on A) are the third antennal segment (A), the labial palps (LB), the labral sense organ (LSO), the ventral cibarial sense organ (V), and the maxillary palps (MX). The arrow onC indicates neuronal expression associated with a wing gustatory sensillum. In the brain, structures strongly labeled with TAU (shown on B) are the mushroom bodies (MB;arrow on D) and the antennal lobes (AL). Scale bar, 25 μm.

Fig. 4.

lacZ Expression ofVoila¹ in female (A) and male (B) prothoracic legs. Each picture is a composition showing the tibia (top) and upper tarsal segments (bottom) of Voila¹ UAS-lacZ4-d-old flies. Arrowheads indicate some of the taste bristles that are always associated with neuronal labeling. Scale bar, 25 μm.