Biology subjects

von Philipsborn, A. C.

Publications and source records attributed to von Philipsborn, A. C..

6 recordsLinked to original sources

bioRxiv2026

Female acoustic signaling of sexual immaturity depresses male courtship in Drosophila

In an early phase of life, most animals are behaviorally and physiologically not yet able to reproduce but show adaptations specific to a juvenile state. In Drosophila females, sexual maturation after metamorphosis is achieved by acquiring receptivity to male courtship and completing oogenesis, a transition that is under hormonal control and requires coordinates changes in the nervous system. Here, we show that immature females display a transient signaling behavior during the time window of asexuality by flicking their wings in response to and dependent on male courtship stimuli. Immature wing flicks require the activity of Doublesex (Dsx) expressing central brain pC1a neurons that mediate receptivity in mature virgins. Immature wing flicks generate patterned sound pulse trains that differ from other intraspecific acoustic signals, but resemble pulses produced during mature male agonistic interactions. Courting males exposed to immature flicks shorten courtship singing and abstain from copulation attempts, indicating that immature wing flicks serve as an effective rejection signal of asexual females to minimize futile male mating pursuits.

animal behavior and cognition↗

bioRxiv2026

Abdominal-B regulates the male seminal fluid transferome and new female fecundity factors required for sperm sex peptide binding

Seminal fluid proteins determine reproductive success in a wide range of animals. In the Drosophila male accessory gland, seminal fluid is mainly produced by two cell types, a vast majority of main cells and a small number of secondary cells that possess a specialized secretory apparatus with unusually enlarged dense core granule vesicles. Loss of Abdominal-B expression from secondary cells in the enhancer mutant iab-6cocu disrupts their transcriptional and secretory identity. Consequently, mutant males fail to induce the long-term post-mating response in females, which is characterized by a loss of receptivity and sustained egg laying. Here, we determine how secondary cells shape the seminal transferome and the female response by assessing iab-6cocu male accessory gland and female mate reproductive tract proteomes. We find downregulation of seminal fluid proteins that constitute a signaling network that enables sperm binding and the sustained action of the key regulator Sex peptide and identify two new Sex peptide network proteins crucial for female fecundity, Cornutus (CG1701) and Hanrej (CG42564). Cornutus is required for mating dependent dense core granule vesicle release, providing a link between the products of these compartments and the female long-term post-mating response. Our data highlights the importance of secondary cell signaling and secretion for overall seminal fluid composition and Sex peptide network function as well as the interdependence of main and secondary cells and their secretory products, advancing the general understanding of how seminal fluid signaling pathways modulate female physiology, sperm use and offspring production.

physiology↗

bioRxiv2025

Correlated Gene Copy Number Changes in a Seminal Fluid Protein Network in Drosophila

Reproductive proteins often diverge rapidly between species, yet network function must be maintained. Shared selective pressures on network members and compensatory changes between members can drive their parallel evolutionary trajectories. Indeed, correlated evolutionary rates of amino acid sequence change have been observed for interacting reproductive proteins. But whether gene copy number changes also correlate has not been widely studied. Here, we investigated copy number variation (CNV) of genes in the Drosophila Sex Peptide Seminal Fluid Protein (Sfp) network. Previous research analyzed CNV of the Sfp Sex Peptide (SP) in Drosophila species. We focus on 9 other Sfps whose function is required to mediate the binding of SP to sperm in D. melanogaster which is required for persistence of female post-mating responses. To exhaustively annotate CNV of genes, we developed a computational pipeline pairing iterative protein queries to genome sequence searches with phylogenetic clustering to resolve homology relationships. We observed that the Sfp networks genes are ancestral to Drosophila and that there were repeated duplications and losses of network members across the genus. We detect statistically significant correlations in gene duplication or loss events among network proteins, and show this can be used to identify new members of the network. We also investigated CNV of female-derived proteins that act downstream of the SP sperm-binding network to modulate SP function, these proteins showed no significant correlation of gene turnover events with SP or its network. Our results provide insight into how evolving reproductive genes tolerate duplication and loss, and how network relationships could constrain reproductive protein evolution. Significance StatementReproductive proteins often diverge rapidly between species, yet network function must be maintained. Shared selective pressures on network members and compensatory changes between members can drive their parallel evolutionary trajectories. We report correlated gene duplication and loss among members of the Drosophila Sex Peptide seminal fluid protein network, suggesting that duplication or loss events may drive corresponding events in other network genes. This work is a natural extension of the idea of evolutionary rate covariation, but instead of scoring rates of substitution it tracks correlated duplication and loss events on the phylogeny. Applied to the Sex Peptide network, the method reveals striking patterns, especially for coordinated loss, and identifies a new network gene that is experimentally confirmed.

evolutionary biology↗

bioRxiv2024

Titin-dependent biomechanical feedback tailors sarcomeres to specialised muscle functions in insects

Sarcomeres are the contractile units of muscles that enable animals to move. Insect muscles are remarkable examples because they use extremely different contraction frequencies (ranging from [~]1 to 1000 Hz) and amplitudes for flying, walking and crawling. This is puzzling because sarcomeres are built from essentially the same actin-myosin components. We show here that the giant protein titin is the key to this functional specialisation. I-band titin spans and determines the length of the sarcomeric I-band, and occurs in muscle-type-specific isoforms. Surprisingly, it also rules the length of the force-generating myosin filament in a force feedback mechanism, even though it is not present there. We provide evidence for this model and its validity beyond insects. SummaryHere we identified a mechanical mechanism that instructs sarcomeres to fulfill the specific needs of different muscle types.

developmental biology↗

bioRxiv2023

GABAergic signaling shapes multiple aspects of Drosophila courtship motor behavior

Inhibitory neurons are essential for nervous system function. GABA is the most important neurotransmitter for fast neuronal inhibition in vertebrates and invertebrates. GABAergic signaling in sex specific, fruitless expressing neuronal circuits of Drosophila is required for multiple aspects of male courtship behavior. RNAi mediated knockdown of the GABA producing enzyme Gad1 and the ionotropic receptor Rdl in the ventral nerve cord causes uncoordinated and futile copulation attempts, defects in wing extension choice and severe alterations of courtship song. Altered song of GABA depleted males fails to stimulate female receptivity, but rescue of song patterning alone is not sufficient to rescue male mating success. Knockdown of Gad1 and Rdl in brain circuits abolishes courtship conditioning. We characterize the around 220 neurons coexpressing Gad1 and Fruitless in the Drosophila male nervous system and propose inhibitory circuit motifs underlying key features of courtship behavior based on the observed phenotypes.

neuroscience↗

bioRxiv2019

Foraging fruit flies mix navigational and learning-based decision-making strategies

Animals often navigate environments that are uncertain, volatile and complex, making it challenging to locate reliable food sources. Therefore, it is not surprising that many species evolved multiple, parallel and complementary foraging strategies to survive. Current research on animal behavior is largely driven by a reductionist approach and attempts to study one particular aspect of behavior in isolation. This is justified by the huge success of past and current research in understanding neural circuit mechanisms of behaviors. But focusing on only one aspect of behaviors obscures their inherent multidimensional nature. To fill this gap we aimed to identify and characterize distinct behavioral modules using a simple reward foraging assay. For this we developed a single-animal, trial-based probabilistic foraging task, where freely walking fruit flies experience optogenetic sugar-receptor neuron stimulation. By carefully analyzing the walking trajectories of flies, we were able to dissect the animals foraging decisions into multiple underlying systems. We show that flies perform local searches, cue-based navigation and learn task relevant contingencies. Using probabilistic reward delivery allowed us to bid several competing reinforcement learning (RL) models against each other. We discover that flies accumulate chosen option values, forget unchosen option values and seek novelty. We further show that distinct behavioral modules -learning and navigation-based systems-cooperate, suggesting that reinforcement learning in flies operates on dimensionality reduced representations. We therefore argue that animals will apply combinations of multiple behavioral strategies to generate foraging decisions.

neuroscience↗