Male Drosophila Research Articles

Nutrient conditions sensed by the reproductive organ during development optimize male fecundity in Drosophila.

Nutrient conditions affect the reproductive potential and lifespan of many organisms through the insulin signaling pathway. Although this is well characterized in female oogenesis, nutrient-dependent regulation of fertility/fecundity in males is not known. Seminal fluid components synthesized in the accessory gland are required for high fecundity in Drosophila males. The accessory gland is composed of two types of binucleated cells: a main cell and a secondary cell (SC). The transcription factors Defective proventriculus (Dve) and Abdominal-B (Abd-B) are strongly expressed in adult SCs, whose functions are essential for male fecundity. We found that gene expression of both Dve and Abd-B was down-regulated under nutrient-poor conditions. In addition, nutrient conditions during the pupal stage affected the size and number of SCs. These morphological changes clearly correlated with fecundity, suggesting that SCs act as nutrient sensors. Here, we provide evidence that Dve associates nutrient conditions with optimal reproductive potential in a target of rapamycin signaling-dependent manner.

Chronic unpredictable mild stress-induced depressive-like behavior and dysregulation of brain levels of biogenic amines in Drosophila melanogaster

The etiopathogenesis of depression may involve repeated exposure to several unpredictable stressors. This study was conducted to investigate changes induced by chronic unpredictable mild stress (CUMS) and to assess behavioral and neurochemical changes that predict depressive-like behavior in Drosophila melanogaster. Male Drosophila melanogaster flies were exposed to CUMS with several stressors (cold, heat, starvation, and sleep deprivation) in an unpredictable and chronic manner for ten days. At the end of treatment, in vivo behavioral tests (open field, aggression, forced swimming, mating, light/dark box, male fertility evaluation, sucrose preference, weight evaluation) and ex vivo analyses (dopamine and serotonin levels) were performed. Using this CUMS model, we obtained results that contribute to the construction of a depressive model in Drosophila, where we reproduce some behavioral phenotypes corresponding to depressive symptoms, such as immobility in the forced swimming test, less exploration in the light/dark test, changes in mating behavior, changes in the aggressiveness test, reduced sucrose preference, and weight-loss, in addition to a significant reduction in the levels of serotonin and dopamine when compared to the control group. Fluoxetine was used in our study as a positive control to demonstrate that CUMS-induced depressive-like behaviors in flies can be reversed by antidepressants. In conclusion, male Drosophila melanogaster exposed to CUMS display a depressive-like phenotype, and, while this poses some limitations as an animal model for depression, it meets some of the criteria required to be a valid model, such as good face and construct validity.

Brains, not biochemistry, speed up hot flies

![Figure][1] A small male Drosophila melanogaster fly. By Andre Karwath aka Aka (own work) [CC BY-SA 2.5], via Wikimedia Commons. It's a predicament to which warm-blooded (endothermic) animals cannot relate: the sun nips out from behind a cloud and suddenly your entire metabolism bursts

Transcriptional modulation of entire chromosomes: dosage compensation

Dosage compensation is a regulatory system designed to equalize the transcription output of the genes of the sex chromosomes that are present in different doses in the sexes (X or Z chromosome, depending on the animal species involved). Different mechanisms of dosage compensation have evolved in different animal groups. In Drosophila males, a complex (male-specific lethal) associates with the X chromosome and enhances the activity of most X-linked genes by increasing the rate of RNAPII elongation. In Caenorhabditis, a complex (dosage compensation complex) that contains a number of proteins involved in condensing chromosomes decreases the level of transcription of both X chromosomes in the XX hermaphrodite. In mammals, dosage compensation is achieved by the inactivation, early during development, of most X-linked genes on one of the two X chromosomes in females. The mechanism involves the synthesis of an RNA (Tsix) that protects one of the two Xs from inactivation, and of another RNA (Xist) that coats the other X chromosome and recruits histone and DNA modifying enzymes. This review will focus on the current progress in understanding the dosage compensation mechanisms in the three taxa where it has been best studied at the molecular level: flies, round worms and mammals.

Increase in viability due to the accumulation of X chromosome mutations in Drosophila melanogaster males.

To increase our understanding of the role of new X-chromosome mutations in adaptive evolution, single-X Drosophila melanogaster males were mated with attached-X chromosome females, allowing the male X chromosome to accumulate mutations over 28 generations. Contrary to our hypothesis that male viability would decrease over time, due to the accumulation and expression of X-linked recessive deleterious mutations in hemizygous males, viability significantly increased. This increase may be attributed to germinal selection and to new X-linked beneficial or compensatory mutations, possibly supporting the faster-X hypothesis.

Dynamic changes in ejaculatory bulb size during Drosophila melanogaster aging and mating

The ejaculatory bulb of Drosophila melanogaster males produces proteins and pheromones that play important roles in reproduction. This tissue is also the final mixing site for the ejaculate before transfer to the female. The ejaculatory bulb’s dynamics remain largely unstudied. By microscopy of the ejaculatory bulb in maturing adult males, we observed that the ejaculatory bulb expands in size as males age. Moreover, we document that when males mate, their ejaculatory bulb expands further as ejaculate transfer begins, and then contracts halfway through the course of mating as ejaculate transfer finishes. Although there is some male-to-male variation in the timing of these changes, ultimately the tissue changes in a predictable pattern that gives insight into the active mating process in Drosophila.

Cereblon Maintains Synaptic and Cognitive Function by Regulating BK Channel.

Mutations in the cereblon (CRBN) gene cause human intellectual disability, one of the most common cognitive disorders. However, the molecular mechanisms of CRBN-related intellectual disability remain poorly understood. We investigated the role of CRBN in synaptic function and animal behavior using male mouse and Drosophila models. Crbn knock-out (KO) mice showed normal brain and spine morphology as well as intact synaptic plasticity; however, they also exhibited decreases in synaptic transmission and presynaptic release probability exclusively in excitatory synapses. Presynaptic function was impaired not only by loss of CRBN expression, but also by expression of pathogenic CRBN mutants (human R419X mutant and Drosophila G552X mutant). We found that the BK channel blockers paxilline and iberiotoxin reversed this decrease in presynaptic release probability in Crbn KO mice. In addition, paxilline treatment also restored normal cognitive behavior in Crbn KO mice. These results strongly suggest that increased BK channel activity is the pathological mechanism of intellectual disability in CRBN mutations.SIGNIFICANCE STATEMENTCereblon (CRBN), a well known target of the immunomodulatory drug thalidomide, was originally identified as a gene that causes human intellectual disability when mutated. However, the molecular mechanisms of CRBN-related intellectual disability remain poorly understood. Based on the idea that synaptic abnormalities are the most common factor in cognitive dysfunction, we monitored the synaptic structure and function of Crbn knock-out (KO) animals to identify the molecular mechanisms of intellectual disability. Here, we found that Crbn KO animals showed cognitive deficits caused by enhanced BK channel activity and reduced presynaptic glutamate release. Our findings suggest a physiological pathomechanism of the intellectual disability-related gene CRBN and will contribute to the development of therapeutic strategies for CRBN-related intellectual disability.

Wolbachia affects sleep behavior in Drosophila melanogaster

Wolbachia are endosymbiotic bacteria present in a wide range of insects. Although their dramatic effects on host reproductive biology have been well studied, the effects of Wolbachia on sleep behavior of insect hosts are not well documented. In this study, we report that Wolbachia infection caused an increase of total sleep time in both male and female Drosophila melanogaster. The increase in sleep was associated with an increase in the number of nighttime sleep bouts or episodes, but not in sleep bout duration. Correspondingly, Wolbachia infection also reduced the arousal threshold of their fly hosts. However, neither circadian rhythm nor sleep rebound following deprivation was influenced by Wolbachia infection. Transcriptional analysis of the dopamine biosynthesis pathway revealed that two essential genes, Pale and Ddc, were significantly upregulated in Wolbachia-infected flies. Together, these results indicate that Wolbachia mediates the expression of dopamine related genes, and decreases the sleep quality of their insect hosts. Our findings help better understand the host-endosymbiont interactions and in particular the Wolbachia’s impact on behaviors, and thus on ecology and evolution in insect hosts.

The "unguarded-X" and the genetic architecture of lifespan: Inbreeding results in a potentially maladaptive sex-specific reduction of female lifespan in Drosophila melanogaster.

Sex differences in ageing and lifespan are ubiquitous in nature. The "unguarded-X" hypothesis (UXh) suggests they may be partly due to the expression of recessive mutations in the hemizygous sex chromosomes of the heterogametic sex, which could help explain sex-specific ageing in a broad array of taxa. A prediction central to the UX hypothesis is that inbreeding will decrease the lifespan of the homogametic sex more than the heterogametic sex, because only in the former does inbreeding increase the expression of recessive deleterious mutations. In this study, we test this prediction by examining the effects of inbreeding on the lifespan and fitness of male and female Drosophila melanogaster across different social environments. We found that, across social environments, inbreeding resulted in a greater reduction of female than male lifespan, and that inbreeding effects on fitness did not seem to counterbalance sex-specific effects on lifespan, suggesting the former are maladaptative. Inter- and intra-sexual correlation analyses also allowed us to identify evidence of an underlying joint genetic architecture for inbreeding effects on lifespan. We discuss these results in light of the UXh and other alternative explanations, and suggest that more attention should be paid to the possibility that the "unguarded-X" may play an important role in the evolution of sex-specific lifespan.

Culex pipiens crossing type diversity is governed by an amplified and polymorphic operon of Wolbachia

Culex pipiens mosquitoes are infected with Wolbachia (wPip) that cause an important diversity of cytoplasmic incompatibilities (CIs). Functional transgenic studies have implicated the cidA-cidB operon from wPip and its homolog in wMel in CI between infected Drosophila males and uninfected females. However, the genetic basis of the CI diversity induced by different Wolbachia strains was unknown. We show here that the remarkable diversity of CI in the C. pipiens complex is due to the presence, in all tested wPip genomes, of several copies of the cidA-cidB operon, which undergoes diversification through recombination events. In 183 isofemale lines of C. pipiens collected worldwide, specific variations of the cidA-cidB gene repertoires are found to match crossing types. The diversification of cidA-cidB is consistent with the hypothesis of a toxin–antitoxin system in which the gene cidB co-diversifies with the gene cidA, particularly in putative domains of reciprocal interactions.

Physicochemical characterization of polysaccharides from Chlorella pyrenoidosa and its anti-ageing effects in Drosophila melanogaster

The physicochemical characteristics and in vitro antioxidant and in vivo anti-ageing activities of partial purified Chlorella pyrenoidosa polysaccharides (PCPPs) were investigated. The building blocks of PCPPs were mainly composed of D-glucose, D-galactose and D-mannose. The average molecular weight of PCPPs was 9,950 Da. In vitro antioxidant activity assays showed that PCPPs could effectively scavenge hydroxyl, 1,1-diphenyl-2-picrylhydrazyl, and superoxide radicals, with stronger effect on hydroxyl radicals. Furthermore, the mean lifespan of the male and female Drosophila melanogaster was extended by 11.5% and 10.6%, respectively. This was accompanied by an increase in the total activity of the endogenous antioxidant enzymes, superoxide dismutase, glutathione peroxidase, and catalase in young or old D. melanogaster administered with PCPPs. Moreover, a gender-dependent difference was observed both in lifespan and antioxidant enzyme activities in D. melanogaster. The results indicated that C. pyrenoidosa polysaccharides are potential natural antioxidants in extending lifespan.

Isolation of Aggressive Behavior Mutants in Drosophila Using a Screen for Wing Damage.

Aggression is a complex social behavior that is widespread in nature. To date, only a limited number of genes that affect aggression have been identified, in large part because the complexity of the phenotype makes screening difficult and time-consuming regardless of the species that is studied. We discovered that aggressive group-housed Drosophila melanogaster males inflict damage on each other's wings, and show that wing damage negatively affects their ability to fly and mate. Using this wing-damage phenotype, we screened males from ∼1400 chemically mutagenized strains and found ∼40 mutant strains with substantial wing damage. Five of these mutants also had increased aggressive behavior. To identify the causal mutation in one of our top aggressive strains, we used whole-genome sequencing and genomic duplication rescue strategies. We identified a novel mutation in the voltage-gated potassium channel Shaker (Sh) and show that a nearby previously identified Sh mutation also results in increased aggression. This simple screen can be used to dissect the molecular mechanisms underlying aggression.

Asymmetric Histone Incorporation During DNA Replication in <i>Drosophila </i>Male Germline Stem Cells

Many stem cells undergo asymmetric division to produce both a self-renewing stem cell and a differentiating daughter cell. We previously reported that in male Drosophila germline stem cells (GSCs), preexisting (old) histone H3 is segregated to the self-renewed stem cell, whereas the daughter incorporates newly synthesized (new) H3. Here, we show that histone H4 is likewise segregated asymmetrically, while histones H2A and H2B are segregated symmetrically. Using superresolution imaging, we visualize spatially separable old and new H3 distributions in interphase GSC nuclei and on isolated replicating chromatin fibers. Furthermore, using both superresolved chromatin fibers and proximity ligation assay, we demonstrate that old H3 are preferentially retained on the leading strand while new H3 preferentially associate with the lagging strand. Finally, using a dual nucleoside analog incorporation assay, the temporal separation between leading strand and lagging strand synthesis is detectable. Together, these results demonstrate that the spatial and temporal asymmetries inherent to DNA replication may serve to bias histone incorporation, suggesting an unappreciated role for DNA replication in asymmetrically dividing cells.

Drosophila Endurance Training and Assessment of Its Effects on Systemic Adaptations

Exercise induces beneficial systemic adaptations that reduce the incidence of age-related diseases. However, the molecular pathways that elicit these adaptations are not well understood. Understanding the molecular mechanisms that underlie the exercise response can lead to widely beneficial therapies. Large populations, relatively short lifespan, and easily modifiable genetics make Drosophila a well-suited model system for complex, longitudinal studies. We have developed an enforced climbing apparatus for Drosophila, known as the Power Tower, for the study of systemic exercise adaptations. The Power Tower takes advantage of the fly's natural instinct for negative geotaxis, an innate behavior to run upwards after being tapped to the bottom of their vial. Flies will continuously run either to the point of exhaustion or until the machine is turned off, whichever comes first. After 3 weeks of exercise, male Drosophila adapt to training with a number of conserved, easily quantifiable physiological improvements similar to those seen in mammalian models and humans. Here, we describe a useful endurance training protocol and a suite of post-training assessments that effectively quantify training effects.

Changes in courtship behaviour following rejection: The influence of female phenotype in Drosophila melanogaster

AbstractCourtship can be costly and so selection should favour individual males that reduce courtship towards female types that have a low probability of resulting in copulation. One way males can do this is by associating previous courtship failure with the traits of particular rejecting females. We characterised changes in male Drosophila melanogaster courtship behaviour following a failed mating attempt with one of the four female phenotypes that varied in size, age or mating status. To do this, we assessed individual courtship behaviour for each male presented again with a female of the same phenotype that previously rejected him. Males reduced subsequent courtship most strongly for recently mated (sexually non‐receptive) females. More interestingly, males also significantly reduced courtship activity following a failed mating experience from old females but did not do so for control (large, young, virgin) or small females. As such, males significantly reduced courtship towards both female types possessing chemical cues associated with their phenotype (age and mating status), but not towards a female phenotype based on physical characteristics (body size). Our results suggest that males are able to modify their courtship behaviour following experience, but that they are better prepared to associate chemical traits that may be more reliable indicators of the likelihood of courtship failure.

The trend of courtship and mating behavior of Drosophila melanogaster fitT15 mutants based on caloric restriction

The nutrients gleaned from an organism's diet provide the metabolic energy necessary for normal physiological function. If an organism is unable to consume the required nutrients, then its normal behavior and metabolic activity will be impaired. This study employs Drosophila melanogaster as a model to study the effect of diet restriction on courtship and mating behaviors. To investigate the proposed link between diet and reproduction, samples of male and female fitT15 (female-specific independent of transformer) Drosophila were subjected to two diets: a 100% Standard diet and a 50% Standard diet containing indigestible cellulose. Previous work has shown that these null fit mutants have inappropriate male courtship behavior; however, effects of the mutation for female Drosophila are not currently known. Mutant males and females fed one diet were paired with Canton-S flies fed the 100% Standard diet. Reproductive capabilities were assayed in terms of courtship latency, courtship index, and mating latency. Theoretically, flies on the restricted diet were expected to exhibit higher courtship and mating latencies and lower courtship indices. As of yet, significant differences between these times for the diets have not been demonstrated; however, experimental female flies on the 50% diet have exhibited a trend toward higher courtship and mating latencies when compared to the 100% control specimens. In general, it is possible that diet restriction may have a physiological effect on reproduction.

Gene CG15630 (fipi) is involved in regulation of the interpulse interval in Drosophila courtship song

To study the central pattern generators functioning, previously we identified genes, whose neurospecific knockdowns led to deviations in the courtship song of Drosophila melanogaster males. Reduced expression of the gene CG15630 caused a decrease in the interpulse interval. To investigate the role of CG15630, which we have called here fipi (factor of interpulse interval), in the courtship song production, at first, we have characterized fipi transcripts and protein (FIPI) in the mutant flies carrying P insertion and deletions in this gene and in flies with its RNAi knockdown. FIPI is homologous to the mammalian NCAM2 protein, an important factor of neuronal development in the olfactory system. In this study, we have revealed that local fipi knockdown in the antennal olfactory sensory neurons (OR67d and IR84a), which are responsible for reception of chemosignals modulating courtship behavior, alters the interpulse interval in the opposite directions. Thus, a proper fipi expression seems to be necessary for perception of sexual chemosignals, and the effect of fipi knockdown on IPI value depends on the type of chemoreceptor neurons affected.

Gene expression changes in male accessory glands during ageing are accompanied by reproductive decline in Drosophila melanogaster.

Senescence is accompanied by loss of reproductive functions. Here, we studied reproductive ageing in Drosophila melanogaster males and asked whether the expected decline in male reproductive success is due to diminished functionality of the male accessory gland (AG). The male AG produces the majority of seminal fluid proteins (SFPs) transferred to the female at mating. SFPs induce female postmating changes and are key to male reproductive success. We measured age-dependent gene expression changes for five representative SFP genes in males from four different age groups ranging from 1 to 6weeks after eclosion. Simultaneously, we also measured male reproductive success in postmating traits mediated by transfer of these five SFPs. We found a decreased in male SFP gene expression with advancing age and an accompanying decline in male postmating success. Hence, male reproductive senescence is associated with a decline in functionality of the male AG. While overall individual SFP genes decreased in expression, our results point towards the idea that the composition of an ejaculate might change with male age as the rate of change was variable for those five genes.

Octopamine Drives Endurance Exercise Adaptations in Drosophila

Endurance exercise is an effective therapeutic intervention with substantial pro-healthspan effects. Male Drosophila respond to a ramped daily program of exercise by inducing conserved physiological responses similar to those seen in mice and humans. Female flies respond to an exercise stimulus but donot experience the adaptive training response seen in males. Here, we use female flies as a modelto demonstrate that differences in exercise response are mediated by differences in neuronal activity. The activity of octopaminergic neurons is specifically required to induce the conserved cellular and physiological changes seen following endurance training. Furthermore, either intermittent, scheduled activation of octopaminergic neurons or octopamine feeding is able to fully substitute for exercise, conferring a suite of pro-healthspan benefits to sedentary Drosophila. These experiments indicate that octopamine is a critical mediator of adaptation to endurance exercise in Drosophila.

Metabolic and functional phenotypic profiling of Drosophila melanogaster reveals reduced sex differentiation under stressful environmental conditions

Strong sexual dimorphism is commonly observed across species and, e.g., trade-offs between reproduction and maintenance are thought to explain this dimorphism. Here we test how the metabolic and functional phenotypic responses to varying types of environmental stress differ in male and female Drosophila melanogaster (Diptera: Drosophilidae), and how stress impacts the magnitude of sexual dimorphism. Experimental stressors that we exposed flies to during development were heat stress, poor nutrition, high acidity, high levels of ammonia and ethanol. Emerged male and female flies from the different rearing regimes were investigated using nuclear magnetic resonance (NMR) metabolomics and assessed for body mass and viability. Our results showed that environmental stress leads to reduced sexual dimorphism in both metabolic composition and body mass compared to the level of dimorphism observed at benign conditions. This reduced sexual dimorphism in stressful environments might be caused by a lower investment in sex-specific characteristics under such conditions, and our results provide support for the longstanding idea that ecological factors are important for shaping sexual dimorphism and possibly sexual selection. (Less)