Males have finite resources to spend on reproduction. Thus, males rely on a ‘time investment strategy’ to maximize their reproductive success. For example, male Drosophila melanogaster extends their mating duration when surrounded by conditions enriched with rivals. Here we report a different form of behavioral plasticity whereby male fruit flies exhibit a shortened duration of mating when they are sexually experienced; we refer to this plasticity as ‘shorter-mating-duration (SMD)’. SMD is a plastic behavior and requires sexually dimorphic taste neurons. We identified several neurons in the male foreleg and midleg that express specific sugar and pheromone receptors. Using a cost-benefit model and behavioral experiments, we further show that SMD behavior exhibits adaptive behavioral plasticity in male flies. Thus, our study delineates the molecular and cellular basis of the sensory inputs required for SMD; this represents a plastic interval timing behavior that could serve as a model system to study how multisensory inputs converge to modify interval timing behavior for improved adaptation.

Backgrounds Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disorder characterized by motor neuron degeneration in the primary motor neurons. C9orf72 repeat expansion mutation is the most prevalent genetic causes of ALS/FTD. Due to the complexity of ALS, there has been no successful therapy for the condition. The traditional neurocentric concept of ALS derives in part from the assumption that the degradation of motor neuron (MN) cells in ALS is driven by cell-autonomous mechanisms, however, recent research has focused on the non-cell-autonomous pathogenic mechanisms such as glial, immune cells and blood-brain barriers participate in the degeneration of MNs in ALS. Drosophila melanogaster is widely used as a genetic model for ALS, giving essential mechanistic data on disease onset and development. Methods Using newly developed genetic tools to individually mark each subtype of the adult glial system in the fruit fly, we demonstrate that surface glia is the major and the only glial subtypes for the pathogenesis of C9orf72-mediated ALS/FTD. Results The surface glia of flies is the most critical of the six different subtypes of fly glia when it comes to developmental toxicity as well as anomalies in adult locomotion and lifespan. The fact that the expression of DPR in surface glia did not result in the death of neurons or glia in the CNS (Fig. 10) lends credence to the hypothesis that C9orf72-mediated defects in adult physiology are not caused by deficiencies only in the CNS. Conclusion Therefore, understanding the non-cell autonomous pathogenic pathways in ALS requires an understanding of surface glia.

Males have finite resources to spend on reproduction. Thus, males rely on a 'time investment strategy' to maximize their reproductive success. For example, male Drosophila melanogaster extends their mating duration when surrounded by conditions enriched with rivals. Here we report a novel form of behavioral plasticity whereby male fruit flies exhibit a shortened duration of mating when they are sexually experienced; we refer to this plasticity as 'shorter-mating-duration (SMD)'. SMD is a plastic behavior and requires sexually dimorphic taste neurons. We identified several neurons in the male foreleg and midleg that express specific sugar, pheromone and mechanosensory receptors. Using a cost-benefit model and behavioral experiments, we further show that SMD behavior exhibits adaptive behavioral plasticity in male flies. Thus, our study delineates the molecular and cellular basis of the sensory inputs required for SMD; this represents a plastic interval timing behavior that could serve as a model system to study how multisensory inputs converge to modify interval timing behavior for improved adaptation.

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disorder characterized by motor neuron degeneration in the primary motor neurons. C9orf72 repeat expansion mutation is the most prevalent genetic causes of ALS/FTD. Due to the complexity of ALS, there has been no successful therapy for the condition. The traditional neurocentric concept of ALS derives in part from the assumption that the degradation of motor neuron (MN) cells in ALS is driven by cell-autonomous mechanisms, however, recent research has focused on the non-cell-autonomous pathogenic mechanisms such as glial, immune cells and blood-brain barriers participate in the degeneration of MNs in ALS. Drosophila melanogaster is widely used as a genetic model for ALS, giving essential mechanistic data on disease onset and development. Using newly developed genetic tools to individually mark each subtype of the adult glial system in the fruit fly, we demonstrate that surface glia are the major glial subtypes for the pathogenesis of C9orf72-mediated ALS/FTD.

Similar to the human brain, Drosophila glia may well be divided into several subtypes that each carry out specific functions. Glial GPCRs plays key roles in crosstalk between neurons and glia. Drosophila Lgr4 (dLgr4) is a human relaxin receptor homolog involved in angiogenesis, cardiovascular regulation, collagen remodeling, and wound healing. Recent study suggests that ilp7 might be the ligand for Lgr4 and regulates escape behavior of Drosophila larvae. Here we demonstrate that Drosophila Lgr4 expression in glial cells, not neurons, is necessary for early development, adult behavior, and lifespan. Reducing the Lgr4 level in glial cells, but not neurons, disrupts Drosophila development, although knocking down other LGR family members in glia has no impact. Adult-specific knockdown of Lgr4 in glia but not neurons reduce locomotion, male reproductive success, and animal longevity. The investigation of how glial expression of Lgr4 contributes to this behavioral alteration will increase our understanding of how insulin signaling via glia selectively modulates neuronal activity and behavior.

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