Motor Control of Drosophila Courtship Song

SummaryMany animals utilize acoustic signals—or songs—to attract mates. During courtship, Drosophila melanogaster males vibrate a wing to produce trains of pulses and extended tone, called pulse and sine song, respectively. Courtship songs in the genus Drosophila are exceedingly diverse, and different song features appear to have evolved independently of each other. How the nervous system allows such diversity to evolve is not understood. Here, we identify a wing muscle in D. melanogaster (hg1) that is uniquely male-enlarged. The hg1 motoneuron and the sexually dimorphic development of the hg1 muscle are required specifically for the sine component of the male song. In contrast, the motoneuron innervating a sexually monomorphic wing muscle, ps1, is required specifically for a feature of pulse song. Thus, individual wing motor pathways can control separate aspects of courtship song and may provide a “modular” anatomical substrate for the evolution of diverse songs

Rapid Evolution of Sex-Pheromone-producing Enzyme in Drosophila

A wide range of organisms use sex pheromones to communicate with each other and to identify appropriate mating partners. While the evolution of chemical communication has been suggested to cause sexual isolation and speciation, the mechanisms that govern evolutionary transitions in sex pheromone production are poorly understood. Here, we decipher the molecular mechanisms underlying the rapid evolution in the expression of a gene involved in sex pheromone production in Drosophilid flies. Long-chain cuticular hydrocarbons (e.g., dienes) are produced female-specifically, notably via the activity of the desaturase DESAT-F, and are potent pheromones for male courtship behavior in Drosophila melanogaster. We show that across the genus Drosophila, the expression of this enzyme is correlated with long-chain diene production and has undergone an extraordinary number of evolutionary transitions, including six independent gene inactivations, three losses of expression without gene loss, and two transitions in sex-specificity. Furthermore, we show that evolutionary transitions from monomorphism to dimorphism (and its reversion) in desatF expression involved the gain (and the inactivation) of a binding-site for the sex-determination transcription factor, DOUBLESEX. In addition, we documented a surprising example of the gain of particular cis-regulatory motifs of the desatF locus via a set of small deletions. Together, our results suggest that frequent changes in the expression of pheromone-producing enzymes underlie evolutionary transitions in chemical communication, and reflect changing regimes of sexual selection, which may have contributed to speciation among Drosophila

Rapid Evolution of Sex Pheromone-Producing Enzyme Expression in Drosophila

Rapid evolution of gene expression patterns responsible for pheromone production in 24 species of Drosophila was mapped to simple mutations within the regulatory domain of the desatF gene

Sex in flies: what 'body--mind' dichotomy

Abstract Sexual behavior in Drosophila results from interactions of multiple neural and genetic pathways. Male-specific fruitless (fruM) is a major component inducing male behaviors, but recent work indicates key roles for other sex-specific and sex-non-specific components. Notably, malelike courtship by retained (retn) mutant females reveals an intrinsic pathway for male behavior independent of fruM, while behavioral differences between males and females with equal levels of fruM expression indicate involvement of another sex-specific component. Indeed, sex-specific products of doublesex (dsxF and dsxM), that control sexual differentiation of the body, also contribute to sexual behavior and neural development of both sexes. In addition, the single product of the dissatisfaction (dsf) gene is needed for appropriate behavior in both sexes, implying additional complexities and levels of control. The genetic mechanisms controlling sexual behavior are similar to those controlling body sexual development, suggesting biological advantages of modifying an intermediate intrinsic pathway in generation of two substantially different behavioral or morphological states

Nuclear degradation of p53 occurs during down‐regulation of the p53 response after DNA damage

ABSTRACT The principal regulator of p53 stability is HDM2, an E3 ligase that mediates p53 degradation via the ubiquitin‐26S proteasome pathway. The current model holds that p53 degradation occurs exclusively on cytoplasmic proteasomes and hence has an absolute requirement for nuclear export of p53 via the CRM‐1 pathway. However, proteasomes are abundant in both cytosol and nucleus, and no studies have been done to determine under what physiological circumstances p53 degradation might occur in the nucleus. We analyzed HDM2‐mediated degradation of endogenous p53 in the presence of various nuclear export inhibitors of CRM‐1, including leptomycin B (LMB), a noncompetitive, specific, and fast‐acting inhibitor; and HTLV1‐Rex protein, a potent competitive inhibitor. We found that significant HDM2‐mediated p53 degradation took place in the presence of LMB or HTLV1‐Rex, indicating that endogenous p53 degradation occurs locally in the nucleus, in parallel to cytoplasmic degradation. Moreover, p53 null cells that coexpressed export‐defective mutants of p53 and HDM2 retained partial competence for p53 degradation. It is important that nuclear degradation of p53 occurred during the poststress recovery phase of a p53 response, after DNA damage ceased. We propose that the capability of local p53 degradation within the nucleus provides a tighter and faster control during the down‐regulatory phase, when an active p53 program needs to be turned off quickly

Evolution of sexual size dimorphism in the wing musculature of Drosophila

Male courtship songs in Drosophila are exceedingly diverse across species. While much of this variation is understood to have evolved from changes in the central nervous system, evolutionary transitions in the wing muscles that control the song may have also contributed to song diversity. Here, focusing on a group of four wing muscles that are known to influence courtship song in Drosophila melanogaster, we investigate the evolutionary history of wing muscle anatomy of males and females from 19 Drosophila species. We find that three of the wing muscles have evolved sexual dimorphisms in size multiple independent times, whereas one has remained monomorphic in the phylogeny. These data suggest that evolutionary changes in wing muscle anatomy may have contributed to species variation in sexually dimorphic wing-based behaviors, such as courtship song. Moreover, wing muscles appear to differ in their propensity to evolve size dimorphisms, which may reflect variation in the functional constraints acting upon different wing muscles

12A in T2 is a variability “hot-spot.”

<p>(<b>A</b>) Two examples of transverse projections through the T2 neuromere showing the neurite bundles of hemilineages 11A and 11B (magenta) relative to those of 12A (green). The right 12A hemilineages failed to split but the lineage 11 projections were invariant. Lineages from the genotype: <i>w; R26B05-LexA(attP40)/LexAop2-myr</i>::<i>tdTomato-P10; R24B02-GAL4(attP2)/UAS-myr</i>::<i>GFP-P10</i>. (<b>B</b>) Single examples of S3, T1, and T2, showing the effects of expressing UAS-Ubx.Ia. The immature neurite bundles in S3 are consistently transformed toward the unsplit T2 morphology. The 12A neurons in T1 become T2-like with respect to variability in the failure to split and in forming ectopic branches. Percentages shown are for the fraction of hemilineages that split into a dorsal and intermediate bundle and the fraction of split hemilineages that have an ectopic branch. (<b>C</b>) Quantification of anti-Ubx staining for four individuals that showed bilateral asymmetry. A difference in staining intensity was only observed in one of the four individuals. (<b>D</b>) An image stack from one of the four individuals (Sample1), with GFP in green and anti-Ubx in magenta. (<b>E</b>) A single optical section of the sample in D (showing area in the dashed box). Note the Ubx expression in T2 and lack of expression in T1. (<b>F</b>) When Ubx was expressed in 12A neurons in T1 using R24B02-GAL4 with UAS-Ubx.1a, Ubx was detectable (arrows) in the T1 neurons but still very low when compared to the endogenous levels in T2.</p

Other examples of 12A variants.

<p>(<b>A</b>) An example of the ectopic branch phenotype in T1 (compare with the typical T1 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155957#pone.0155957.g002" target="_blank">Fig 2B</a> and the ectopic branch phenotype of T2 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155957#pone.0155957.g003" target="_blank">Fig 3A</a>). All examples were bilaterally symmetrical with a fully formed commissure (arrowhead), in contrast to 12A in T2, which often exhibits bilateral asymmetry. (<b>B</b>) Example of ventral arch routing of the late-born 12A neurons in T2. Compare the branch on the left (arrowhead) with the unoccupied Neuroglian-stained tract on the right (arrow). (<b>C</b>) Transverse optical section of S3 in which 12A shows the T2 morphology (with unsplit bundles). Compare with <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155957#pone.0155957.g006" target="_blank">Fig 6B</a> and the variants of 12A that are missing the intermediate bundle as shown in Figs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155957#pone.0155957.g003" target="_blank">3A</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155957#pone.0155957.g006" target="_blank">6A</a>. (<b>D</b>) Transverse optical section of T1 in which the left bundle fails to split. (<b>E</b>) Two examples of animals with duplicated hemilineages. (<b>F</b>) One of two cases in which one hemilineage ectopically projected all of its neurites to the contralateral side, leaving one T1 hemisegment completely uninnervated by 12A and the other double innervated.</p

Summary of neuroblast clones in T2 examined at 24 hours APF.

<p>Summary of neuroblast clones in T2 examined at 24 hours APF.</p

Single-neuron clones reveal variable development of late-born 12A neurons in T2.

<p>(<b>A</b>) Proportions of single-neuron clones taking either a dorsal or intermediate path in segments T1 or T2. Each bar shows the proportion of clones recovered from heat shocks at the time point on the x-axis. Numbers of clones are indicated above each bar. (<b>B</b>) Transverse optical section of T1 showing a twin-spot MARCM clone at 0 hours APF. Green and magenta show a single-neuron and neuroblast clone from the same neuroblast. The magenta neurons are all born after the green neuron. Neuroglian-labeled tracts are shown in grayscale. (<b>C-H</b>) Single-neuron clones of 12A in T2 at 24h APF. Transverse optical sections are shown on the left, followed by a z-projection of a dorsal substack, then a tracing of the dorsal view. In tracings, green indicates the clone and gray indicates landmarks as seen by anti-Neuroglian staining (magenta). Green asterisks indicate the point most proximal to the cell soma at which the neurite enters the substack. Dashed boxes indicate the core region of the mesothoracic triangle. (<b>C</b>) Example of a 12Ama clone induced at 72h AEL. (<b>D</b>) Example of a 12Amb clone, induced at 72h AEL. Arrow points to arbor originating from a T1 clone that is not part of the traced clone. (<b>E</b>) Example of a 12Amc clone, induced at 72h AEL. Arrows point to unrepressed signal that is not part of the clone. <b>(F</b>) Three examples of 12Ala clones. Note that the top clone routes along the dorsal path while the other two route along the intermediate path. While all three clones produce contralateral projections at the level of the intermediate commissure, only the bottom clone does so at the location of the ectopic branch of the neurite bundle (arrowheads). The top two clones produce this branch at a more anterior location (long arrows). (<b>G</b>) Two examples of 12Alb clones, induced at 96h AEL. Note the upper clone takes the dorsal path, whereas the lower example takes the intermediate path but otherwise looks identical. Arrows point to unrepressed signal from the right hemilineage and is not part of the clone. (<b>H</b>) Four examples of 12Alc clones induced at either 96h or 108h AEL. Projections into the T2 spur (sp) are indicated with brackets. The top two clones take either the intermediate (top) or dorsal (second from the top) path to an intermediate target, after which they look nearly identical and remain ipsilateral. In the third clone, the longitudinal projection jumps across the midline and continues projecting anteriorly. The bottom example shows two 12Alc clones, one on each side. The clone on the right sends a branch across the midline at the same point as the ectopic commissure (arrowheads); compare this example with the full 18h APF patterns in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155957#pone.0155957.g003" target="_blank">Fig 3C</a> and the 0h APF example in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155957#pone.0155957.g003" target="_blank">Fig 3A</a>.</p