Behavior In Drosophila Research Articles

Hierarchical chemosensory regulation of male-male social interactions in Drosophila.

Pheromones regulate male social behaviors in Drosophila, but the identities and behavioral role(s) of these chemosensory signals, and how they interact, are incompletely understood. Here we show that (Z)-7-tricosene (7-T), a male-enriched cuticular hydrocarbon (CH) previously shown to inhibit male-male courtship, is also essential for normal levels of aggression. The opposite influences of 7-T on aggression and courtship are independent, but both require the gustatory receptor Gr32a. Surprisingly, sensitivity to 7-T is required for the aggression-promoting effect of 11-cis-vaccenyl acetate (cVA), an olfactory pheromone, but 7-T sensitivity is independent of cVA. 7-T and cVA therefore regulate aggression in a hierarchical manner. Furthermore, the increased courtship caused by depletion of male CHs is suppressed by a mutation in the olfactory receptor Or47b. Thus, male social behaviors are controlled by gustatory pheromones that promote and suppress aggression and courtship, respectively, and whose influences are dominant to olfactory pheromones that enhance these behaviors.

Remembering Nutrient Quality of Sugar in Drosophila

Taste is an early stage in food and drink selection for most animals [1, 2]. Detecting sweetness indicates the presence of sugar and possible caloric content. However, sweet taste can be an unreliable predictor of nutrient value because some sugars cannot be metabolized. In addition, discrete sugars are detected by the same sensory neurons in the mammalian [3] and insect [4, 5] gustatory systems, making it difficult for animals to readily distinguish the identity of different sugars using taste alone [6-8]. Here we used an appetitive memory assay in Drosophila [9-11] to investigate the contribution of palatability and relative nutritional value of sugars to memory formation. We show that palatability and nutrient value both contribute to reinforcement of appetitive memory. Nonnutritious sugars formed less robust memory that could be augmented by supplementing with a tasteless but nutritious substance. Nutrient information is conveyed to the brain within minutes of training, when it can be used to guide expression of a sugar-preference memory. Therefore, flies can rapidly learn to discriminate between sugars using a postingestive reward evaluation system, and they preferentially remember nutritious sugars.

Drosophila Evaluates and Learns the Nutritional Value of Sugars

Living organisms need to search for and ingest nutritional chemicals, and gustation plays a major role in detecting and discriminating between chemicals present in the environment. Using Drosophila as a model organism, we asked whether animals have the ability to evaluate the nutritional value of sugars. In flies, chemosensilla on the tarsi and labellum are the gustatory organs used to discriminate between edible and nonedible compounds [1, 2]. We noticed that Drosophila do not assign nutritional values to all sweet chemicals. D-arabinose is sweet to flies, but it provides them with no nutrition. By contrast, the sugar alcohol D-sorbitol is not sensed as sweet, but flies can live on it. We performed behavioral and electrophysiological measurements to confirm these gustatory and feeding responses. We found that Drosophila can learn the nutritional value of nonsweet D-sorbitol when it is associated with an odor cue. The learning process involved the synapsin molecule, suggesting that a neuronal mechanism is involved. We propose that Drosophila uses neural machinery to detect, evaluate, and learn the nutritional value of foods after ingestion.

Presynaptic Facilitation by Neuropeptide Signaling Mediates Odor-Driven Food Search

Internal physiological states influence behavioral decisions. We have investigated the underlying cellular and molecular mechanisms at the first olfactory synapse for starvation modulation of food-search behavior in Drosophila. We found that a local signal by short neuropeptide F (sNPF) and a global metabolic cue by insulin are integrated at specific odorant receptor neurons (ORNs) to modulate olfactory sensitivity. Results from two-photon calcium imaging show that starvation increases presynaptic activity via intraglomerular sNPF signaling. Expression of sNPF and its receptor (sNPFR1) in Or42b neurons is necessary for starvation-induced food-search behavior. Presynaptic facilitation in Or42b neurons is sufficient to mimic starvation-like behavior in fed flies. Furthermore, starvation elevates the transcription level of sNPFR1 but not that of sNPF, and insulin signaling suppresses sNPFR1 expression. Thus, starvation increases expression of sNPFR1 to change the odor map, resulting in more robust food-search behavior.

Optogenetics in the teaching laboratory: using channelrhodopsin-2 to study the neural basis of behavior and synaptic physiology in Drosophila.

Here we incorporate recent advances in Drosophila neurogenetics and "optogenetics" into neuroscience laboratory exercises. We used the light-activated ion channel channelrhodopsin-2 (ChR2) and tissue-specific genetic expression techniques to study the neural basis of behavior in Drosophila larvae. We designed and implemented exercises using inexpensive, easy-to-use systems for delivering blue light pulses with fine temporal control. Students first examined the behavioral effects of activating glutamatergic neurons in Drosophila larvae and then recorded excitatory junctional potentials (EJPs) mediated by ChR2 activation at the larval neuromuscular junction (NMJ). Comparison of electrically and light-evoked EJPs demonstrates that the amplitudes and time courses of light-evoked EJPs are not significantly different from those generated by electrical nerve stimulation. These exercises introduce students to new genetic technology for remotely manipulating neural activity, and they simplify the process of recording EJPs at the Drosophila larval NMJ. Relatively little research work has been done using ChR2 in Drosophila, so students have opportunities to test novel hypotheses and make tangible contributions to the scientific record. Qualitative and quantitative assessment of student experiences suggest that these exercises help convey principles of synaptic transmission while also promoting integrative and inquiry-based studies of genetics, cellular physiology, and animal behavior.

Engineered Alterations in RNA Editing Modulate Complex Behavior in Drosophila: REGULATORY DIVERSITY OF ADENOSINE DEAMINASE ACTING ON RNA (ADAR) TARGETS

Select proteins involved in electrical and chemical neurotransmission are re-coded at the RNA level via the deamination of particular adenosines to inosine by adenosine deaminases acting on RNA (ADARs). It has been hypothesized that this process, termed RNA editing, acts to "fine-tune" neurophysiological properties in animals and potentially downstream behavioral outputs. However, the extreme phenotypes resulting from deletions of adar loci have precluded investigations into the relationship between ADAR levels, target transcripts, and complex behaviors. Here, we engineer Drosophila hypomorphic for ADAR expression using homologous recombination. A substantial reduction in ADAR activity (>80%) leads to altered circadian motor patterns and abnormal male courtship, although surprisingly, general locomotor coordination is spared. The altered phenotypic landscape in our adar hypomorph is paralleled by an unexpected dichotomous response of ADAR target transcripts, i.e. certain adenosines are minimally affected by dramatic ADAR reduction, whereas editing of others is severely curtailed. Furthermore, we use a novel reporter to map RNA editing activity across the nervous system, and we demonstrate that knockdown of editing in fruitless-expressing neurons is sufficient to modify the male courtship song. Our data demonstrate that network-wide temporal and spatial regulation of ADAR activity can tune the complex system of RNA-editing sites and modulate multiple ethologically relevant behavioral modalities.

Female Contact Activates Male-Specific Interneurons that Trigger Stereotypic Courtship Behavior in Drosophila

We determined the cellular substrate for male courtship behavior by quasinatural and artificial stimulation of brain neurons. Activation of fruitless (fru)-expressing neurons via stimulation of thermosensitive dTrpA1 channels induced an entire series of courtship acts in male Drosophila placed alone without any courting target. By reducing the number of neurons expressing dTrpA1 by MARCM, we demonstrated that the initiation of courtship behavior is significantly correlated with the activation of the transmidline P1 interneurons, the descending P2b interneurons, or both, indicating that these interneurons trigger courtship. Using an experimental paradigm in which a tethered male can be stimulated to initiate courtship by touching his foreleg tarsus to a female's abdomen, we found that P1 neurites of tethered males showed a transient Ca(2+) rise after tarsal stimulation with the female-associated sensory cues. These observations strongly suggest that P1 neurons are the prime components of the neural circuitry that initiates male courtship.

Neuronal Control of Drosophila Courtship Song

The courtship song of the Drosophila male serves as a genetically tractable model for the investigation of the neural mechanisms of decision-making, action selection, and motor pattern generation. Singing has been causally linked to the activity of the set of neurons that express the sex-specific fru transcripts, but the specific neurons involved have not been identified. Here we identify five distinct classes of fru neuron that trigger or compose the song. Our data suggest that P1 and pIP10 neurons in the brain mediate the decision to sing, and to act upon this decision, while the thoracic neurons dPR1, vPR6, and vMS11 are components of a central pattern generator that times and shapes the song's pulses. These neurons are potentially connected in a functional circuit, with the descending pIP10 neuron linking the brain and thoracic song centers. Sexual dimorphisms in each of these neurons may explain why only males sing.

Assay for Courtship Suppression in Drosophila

INTRODUCTIONUnsuccessful courtship reduces subsequent courtship behavior of male Drosophila. This experience-dependent behavior modification is called courtship conditioning and has been one of the major paradigms used to study learning and memory in Drosophila. This article describes a basic behavioral assay for quantifying short-term memory of courtship suppression induced by training with a mated female.

Reverse engineering in Drosophila larvae - Modeling neural control of learned versus innate behavior

Event Abstract Back to Event Reverse engineering in Drosophila larvae - Modeling neural control of learned versus innate behavior Evren Pamir1, 2*, Michael Schleyer3, Timo Saumweber3, Bertram Gerber3, 4, 5 and Martin P. Nawrot1, 2 1 Freie Universität, Neuroinformatics and Theoretical Neuroscience, Germany 2 Bernstein Center for Computational Neuroscience, Germany 3 Universität Leipzig, Genetics, Institute of Biology, Germany 4 Universität Magdeburg, Behaviour Genetics, Institute of Biology, Germany 5 Leibniz Institute of Neurobiology, Genetics of Learning and Memory, Germany A series of recent behavioral studies have described learned and innate behavior in Drosophila larvae under a variety of experimental conditions (reviewed in Gerber & Stocker, 2007). In order to conceptualize these findings, a qualitative circuit-level model for the regulation of this behavior has been proposed (Schleyer et al., In Press). Here we follow and extend this approach by simulating the processing of olfactory and reinforcing stimuli in a simple sensory-to-motor circuit during olfactory conditioning and during testing of naive behavior. The proposed circuitry is constrained by neuroanatomy, in particular we introduced plastic synapses between mushroom body Kenyon cells and their output neurons, receiving reinforcement signals from the subesophageal ganglion. The expression of behavior is regulated as follows in the circuitry: (i) Innate preference is driven by the net sum of innate appetitive or aversive values of sensory stimuli. (ii) Learned preferences, in contrast, are behaviorally expressed only if this yields a positive gain compared to the acute testing situation. As expected we find that our circuit-model can well reproduce the majority of behavioral observations. In addition the proposed model constitutes a possible control-architecture for a biased random walk of an artificial agent searching for food in a circular arena. We further aim at a more detailed understanding of the extracted behavioral control principles by analyzing trajectories of individual animals recorded under different experimental conditions. Acknowledgements This work was supported by the BMBF through grant 01GQ0941 within the Bernstein Focus Neuronal Basis of Learning (BFNL). E.P was funded by the DFG within the Research Training Group 1589 Sensory Computation in Neural Systems. M.S. was funded by the Studienstiftung des Deutschen Volkes, T.S. by the University of Würzburg Graduate School Life Science. References Gerber B, Stocker RF. (2007) The Drosophila Larva as a Model for Studying Chemosensation and Chemosensory Learning: A Review. Chem. Senses 32: 65–89 Schleyer M, Saumweber T, Nahrendorf W, Fischer B, von Alpen D, Pauls D, Thum A, Gerber B. A behaviour-based circuit-model of how outcome expectations organize learned behavior in larval Drosophila. Learning & Memory, In Press. Keywords: Learning, Locomotion, Olfactory classical conditioning, plasticity Conference: BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011, Freiburg, Germany, 4 Oct - 6 Oct, 2011. Presentation Type: Poster Topic: learning and plasticity (please use "learning and plasticity" as keyword) Citation: Pamir E, Schleyer M, Saumweber T, Gerber B and Nawrot MP (2011). Reverse engineering in Drosophila larvae - Modeling neural control of learned versus innate behavior. Front. Comput. Neurosci. Conference Abstract: BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011. doi: 10.3389/conf.fncom.2011.53.00194 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Aug 2011; Published Online: 04 Oct 2011. * Correspondence: Mr. Evren Pamir, Freie Universität, Neuroinformatics and Theoretical Neuroscience, Berlin, Germany, evren.pamir@lin-magdeburg.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Evren Pamir Michael Schleyer Timo Saumweber Bertram Gerber Martin P Nawrot Google Evren Pamir Michael Schleyer Timo Saumweber Bertram Gerber Martin P Nawrot Google Scholar Evren Pamir Michael Schleyer Timo Saumweber Bertram Gerber Martin P Nawrot PubMed Evren Pamir Michael Schleyer Timo Saumweber Bertram Gerber Martin P Nawrot Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

How outcome expectations organize learned behaviour in larval Drosophila

Event Abstract Back to Event How outcome expectations organize learned behaviour in larval Drosophila Michael Schleyer1, 2*, Timo Saumweber1, 2, Wiebke Nahrendorf2, Benjamin Fischer2, Désirée Von Alpen3, Dennis Pauls3, Andreas S. Thum3 and Bertram Gerber1, 2 1 University of Leipzig, Institute of Biology, Germany 2 University of Würzburg, Department of Neurobiology and Genetics, Germany 3 Université de Fribourg, Switzerland Drosophila larvae combine a numerically simple brain, a correspondingly moderate behavioural complexity and the availability of a rich toolbox for transgenic manipulation. This makes them attractive as a study case when trying to achieve a circuit-level understanding of behaviour organization. From a series of behavioural experiments, we here suggest a circuitry of chemosensory processing, odour-tastant memory trace formation and the ‘decision’ process to behaviourally express these memory traces- or not. The model incorporates statements about the neuronal organization of innate versus conditioned chemosensory behaviour, and the kinds of interaction between olfactory and gustatory pathways during the establishment and behavioural expression of odour-tastant memory traces. It in particular suggests that innate olfactory behaviour is responsive in nature, whereas conditioned olfactory behaviour is captured better when seen as an action in pursuit of its outcome. It incorporates the available neuroanatomical and behavioural data and thus should be useful as scaffold for the ongoing investigations of the chemo-behavioural system in larval Drosophila. References Scherer S, Stocker RF, Gerber B. 2003. Olfactory learning in individually assayed Drosophila larvae. Learn Mem 10: 217-225. Gerber B, Hendel T. 2006. Outcome expectations drive learned behaviour in larval Drosophila. Proc R Soc B 273: 2965-2968. Gerber B, Stocker RF. 2007. The Drosophila larva as a model for studying chemosensation and chemosensory learning: a review. Chem Senses 32: 65-89. Schleyer M, Saumweber T, Nahrendorf W, Fischer B, von Alpen D, Pauls D, Thum A, Gerber B. In press. A behaviour-based circuit-model of how outcome expectations organize learned behavior in larval drosophila. Learn Mem. Keywords: decision-making, Drosophila, Learning and plasticity, memory retrieval, Outcome expectation Conference: BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011, Freiburg, Germany, 4 Oct - 6 Oct, 2011. Presentation Type: Poster Topic: learning and plasticity (please use "learning and plasticity" as keyword) Citation: Schleyer M, Saumweber T, Nahrendorf W, Fischer B, Von Alpen D, Pauls D, Thum AS and Gerber B (2011). How outcome expectations organize learned behaviour in larval Drosophila. Front. Comput. Neurosci. Conference Abstract: BC11 : Computational Neuroscience & Neurotechnology Bernstein Conference & Neurex Annual Meeting 2011. doi: 10.3389/conf.fncom.2011.53.00212 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 17 Aug 2011; Published Online: 04 Oct 2011. * Correspondence: Mr. Michael Schleyer, University of Leipzig, Institute of Biology, Leipzig, 04103, Germany, michael.schleyer@uni-leipzig.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Michael Schleyer Timo Saumweber Wiebke Nahrendorf Benjamin Fischer Désirée Von Alpen Dennis Pauls Andreas S Thum Bertram Gerber Google Michael Schleyer Timo Saumweber Wiebke Nahrendorf Benjamin Fischer Désirée Von Alpen Dennis Pauls Andreas S Thum Bertram Gerber Google Scholar Michael Schleyer Timo Saumweber Wiebke Nahrendorf Benjamin Fischer Désirée Von Alpen Dennis Pauls Andreas S Thum Bertram Gerber PubMed Michael Schleyer Timo Saumweber Wiebke Nahrendorf Benjamin Fischer Désirée Von Alpen Dennis Pauls Andreas S Thum Bertram Gerber Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Evening circadian oscillator as the primary determinant of rhythmic motivation for Drosophila courtship behavior

Circadian clocks of Drosophila melanogaster motivate males to court females at a specific time of day. However, clock neurons involved in courtship rhythms in the brain of Drosophila remain totally unknown. The circadian locomotor behavior of Drosophila is controlled by morning (M cells) and evening (E cells) cells in the brain, which regulate morning and evening activities, respectively. Here, we identified the brain clock neurons that are responsible for the circadian rhythms of the close-proximity (CP) behavior that reflects male courtship motivation. Interestingly, the ablation or functional molecular clock disruption of E cells caused arrhythmic CP behavior, but that of M cells resulted in sustained CP rhythms even in constant darkness. In addition, the ablation of some dorsal lateral neurons (LNd) of E cells using neuropeptide-F (NPF)-GAL4 did not impair CP rhythms. These findings suggested that the NPF-negative LNds and DN1s of E cells include cells essential for circadian CP behavior in Drosophila.

The effects of aging on stem cell behavior in Drosophila

Throughout life, adult stem cells play essential roles in maintaining tissue and organ function by providing a reservoir of cells for homeostasis and regeneration. A decline in stem cell number or activity may, therefore, lead to compromised organ and tissue function that is characteristic of aging. Drosophila has emerged as an ideal system for studying the relationship between stem cells and aging, as it has a short lifespan, tissues that are maintained by adult stem cells, and conserved pathways known to regulate aging. In this review, we highlight recent findings describing intrinsic and extrinsic age-related changes that affect the behavior of Drosophila germline and intestinal stem cells. We also discuss whether pathways affecting lifespan can act autonomously or non-autonomously in stem cells during aging.

The effects of CO 2 and chronic cold exposure on fecundity of female Drosophila melanogaster

Carbon dioxide and chilling are sometimes used to immobilise insects for laboratory research. Both of these methods are known to have short-term effects on behaviour and physiology in Drosophila, but their long-term impacts are unknown. We exposed female D. melanogaster adults to high CO 2 concentrations (4 h at 18,000 ppm) and chronic cold (72 h at 4 °C). The carbon dioxide exposure increased chill coma recovery time, but did not result in changes in offspring number, sex ratio, or size. By contrast, the cold exposure resulted in fewer, smaller offspring, and resulted in a male-biased sex ratio compared to controls. There was no significant interaction between CO 2 and cold. We conclude that although caution must be used in choosing an immobilisation method, CO 2 appears to have less long-term impact than cold.

Assaying locomotor activity to study circadian rhythms and sleep parameters in Drosophila.

Most life forms exhibit daily rhythms in cellular, physiological and behavioral phenomena that are driven by endogenous circadian (≡24 hr) pacemakers or clocks. Malfunctions in the human circadian system are associated with numerous diseases or disorders. Much progress towards our understanding of the mechanisms underlying circadian rhythms has emerged from genetic screens whereby an easily measured behavioral rhythm is used as a read-out of clock function. Studies using Drosophila have made seminal contributions to our understanding of the cellular and biochemical bases underlying circadian rhythms. The standard circadian behavioral read-out measured in Drosophila is locomotor activity. In general, the monitoring system involves specially designed devices that can measure the locomotor movement of Drosophila. These devices are housed in environmentally controlled incubators located in a darkroom and are based on using the interruption of a beam of infrared light to record the locomotor activity of individual flies contained inside small tubes. When measured over many days, Drosophila exhibit daily cycles of activity and inactivity, a behavioral rhythm that is governed by the animal's endogenous circadian system. The overall procedure has been simplified with the advent of commercially available locomotor activity monitoring devices and the development of software programs for data analysis. We use the system from Trikinetics Inc., which is the procedure described here and is currently the most popular system used worldwide. More recently, the same monitoring devices have been used to study sleep behavior in Drosophila. Because the daily wake-sleep cycles of many flies can be measured simultaneously and only 1 to 2 weeks worth of continuous locomotor activity data is usually sufficient, this system is ideal for large-scale screens to identify Drosophila manifesting altered circadian or sleep properties.

Assaying Locomotor Activity to Study Circadian Rhythms and Sleep Parameters in <em>Drosophila</em>

Most life forms exhibit daily rhythms in cellular, physiological and behavioral phenomena that are driven by endogenous circadian (≡24 hr) pacemakers or clocks. Malfunctions in the human circadian system are associated with numerous diseases or disorders. Much progress towards our understanding of the mechanisms underlying circadian rhythms has emerged from genetic screens whereby an easily measured behavioral rhythm is used as a read-out of clock function. Studies using Drosophila have made seminal contributions to our understanding of the cellular and biochemical bases underlying circadian rhythms. The standard circadian behavioral read-out measured in Drosophila is locomotor activity. In general, the monitoring system involves specially designed devices that can measure the locomotor movement of Drosophila. These devices are housed in environmentally controlled incubators located in a darkroom and are based on using the interruption of a beam of infrared light to record the locomotor activity of individual flies contained inside small tubes. When measured over many days, Drosophila exhibit daily cycles of activity and inactivity, a behavioral rhythm that is governed by the animal's endogenous circadian system. The overall procedure has been simplified with the advent of commercially available locomotor activity monitoring devices and the development of software programs for data analysis. We use the system from Trikinetics Inc., which is the procedure described here and is currently the most popular system used worldwide. More recently, the same monitoring devices have been used to study sleep behavior in Drosophila. Because the daily wake-sleep cycles of many flies can be measured simultaneously and only 1 to 2 weeks worth of continuous locomotor activity data is usually sufficient, this system is ideal for large-scale screens to identify Drosophila manifesting altered circadian or sleep properties.

Cellular Organization of the Neural Circuit that Drives Drosophila Courtship Behavior

Courtship behavior in Drosophila has been causally linked to the activity of the heterogeneous set of ∼1500 neurons that express the sex-specific transcripts of the fruitless (fru) gene, but we currently lack an appreciation of the cellular diversity within this population, the extent to which these cells are sexually dimorphic, and how they might be organized into functional circuits. We used genetic methods to define 100 distinct classes of fru neuron, which we compiled into a digital 3D atlas at cellular resolution. We determined the polarity of many of these neurons and computed their likely patterns of connectivity, thereby assembling them into a neural circuit that extends from sensory input to motor output. The cellular organization of this circuit reveals neuronal pathways in the brain that are likely to integrate multiple sensory cues from other flies and to issue descending control signals to motor circuits in the thoracic ganglia. We identified 11 anatomical dimorphisms within this circuit: neurons that are male specific, are more numerous in males than females, or have distinct arborization patterns in males and females. The cellular organization of the fru circuit suggests how multiple distinct sensory cues are integrated in the fly's brain to drive sex-specific courtship behavior. We propose that sensory processing and motor control are mediated through circuits that are largely similar in males and females. Sex-specific behavior may instead arise through dimorphic circuits in the brain and nerve cord that differentially couple sensory input to motor output.

Neurogenetics: Short-Circuiting Sexually Dimorphic Behaviors

It is clear that male and female animals behave differently, but how do those differences arise? New studies show that there are extensive, sex-specific differences in the anatomy of neurons that underlie reproductive behaviors in Drosophila.

Avoiding DEET through Insect Gustatory Receptors

DEET is the most widely used insect repellent worldwide. In Drosophila olfactory receptor neurons (ORNs), DEET is detected through a mechanism employing the olfactory receptor, OR83b. However, it is controversial as to whether ORNs respond directly to DEET or whether DEET blocks the response to attractive odors. Here, we showed that DEET suppressed feeding behavior in Drosophila, and this effect was mediated by gustatory receptor neurons (GRNs). DEET was potent in suppressing feeding as <0.1% DEET elicited aversive behavior. Inhibition of feeding required multiple gustatory receptors (GRs) expressed in inhibitory GRNs. DEET stimulated action potentials in GRNs that respond to aversive compounds, and this response was lost in the Gr32a, Gr33a, and Gr66a mutants. Since 0.02% DEET elicited action potentials, we conclude that DEET directly activates of GRNs. We suggest that the effectiveness of DEET in pest control owes to its dual action in inducing avoidance simultaneously via GRNs and ORNs.

Evolution of the Insect Yellow Gene Family

The yellow gene family is intriguing for a number of reasons. To date, yellow-like genes have only been identified in insect species and a number of bacteria. The function of the yellows is largely unknown, although a few have been associated with melanization and behavior in Drosophila, and a unique clade of genes from Apis mellifera may be involved in caste specification. Here, we show that yellow-like sequences are present in bacteria, insects, and fungi but absent from other eukaryotes apart from isolated putative sequences in Amphioxus, the Salmon Louse, and Naegleria. The yellow-like family forms a discrete gene class characterized by the presence of a major royal jelly protein domain, but eukaryote yellow-like proteins are not monophyletic. The unusual phylogenetic distribution of yellow-like sequences suggests either multiple horizontal transfer from bacteria into eukaryotes or extensive gene loss in eukaryote lineages. Comparative analysis of yellow family synteny and gene order demonstrates that a highly conserved block of three to five genes has been maintained throughout insect diversification despite extensive genome rearrangements. We show strong purifying selection on seven yellow genes over approximately 100 My separating the silkmoth and Heliconius butterflies and an association between spatial regulation of gene expression and distribution of melanic pigment in the developing butterfly wing. A single ancestral yellow-like gene has therefore undergone multiple rounds of duplication within the insects accompanied by functional constraint on both genomic location and protein evolution.