A Panova & Nikolai G Kamyshev (2014) The effect of neurospecific knockdown of candidate genes for locomotor behavior and sound production in Drosophila melanogaster, Fly, 8:3, 176-187, DOI: 10.4161/19336934.2014.983389 To link to this article: https://doi.org/10. 4161/19336934.2014.983389 Molecular mechanisms underlying the functioning of central pattern generators (CPGs) are poorly understood. Investigations using genetic approaches in the model organism Drosophila may help to identify unknown molecular players participating in the formation or control of motor patterns. Here we report Drosophila genes as candidates for involvement in the neural mechanisms responsible for motor functions, such as locomotion and courtship song. Twenty-two Drosophila lines, used for gene identification, were isolated from a previously created collection of 1064 lines, each carrying a P element insertion in one of the autosomes. The lines displayed extreme deviations in locomotor and/or courtship song parameters compared with the whole collection. The behavioral consequences of CNS-specific RNAi-mediated knockdowns for 10 identified genes were estimated. The most prominent changes in the courtship song interpulse interval (IPI) were seen in flies with Sps2 or CG15630 knockdown. Glia-specific knockdown of these genes produced no effect on the IPI. Estrogen-induced knockdown of CG15630 in adults reduced the IPI. The product of the CNS-specific gene, CG15630 (a predicted cell surface receptor), is likely to be directly involved in the functioning of the CPG generating the pulse song pattern. Future studies should ascertain its functional role in the neurons that constitute the song CPG. Other genes (Sps2, CG34460), whose CNS-specific knockdown resulted in IPI reduction, are also worthy of detailed examination.

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.

Previous social experience may affect subsequent behavior. It was shown by other authors that Drosophila melanogaster males kept individually are more aggressive and sexually active than males kept in a group. In the present study, we tested the locomotor activity of individual males and females previously reared either individually, or in a group. We found that keeping 20 young males for three days together led to a strong long-term (up to 5 days) reduction in their further locomotor activity as individuals. Rearing of young males in groups of other sizes (2, 5, 10, and 30) produced a smaller or no after-effect. At the same time, we have not found any difference in subsequent behavior of individual females previously kept either individually, or in a group. We suppose that in a group, flies learned to suppress their locomotor activity to prevent unpleasant contacts with other animals (operant learning). It seems that in males this learning is more efficient because of the higher level of aggression producing the stronger negative reinforcement.

For about half a century Drosophila has served as a model subject in biomedical research in the influence of spaceflight factors on genome stability, lifespan, metabolism and immunity. Up to now behavioral investigations have been performed either with offspring of flies that had been to space or directly with flies onboard the International Space Station (ISS). Ours is the first research providing evidence that upon return to the Earth after the spaceflight to the ISS, drosophila males show impaired geotaxis, reduced locomotor activity and decreased courtship intensity. The behavioral changes retain for at least two weeks. The main stress factor during the spaceflight is microgravity. Under these conditions living organisms are less able to control posture and goal-directed movements. Microgravity disturbs warm air convection that may cause local changes in oxygen-carbon dioxide balance. This creates unfavorable conditions in vials worsening the physiological state of flies that may influence the results of postflight tests.

Drosophila melanogaster is a popular model organism in the study of memory due to a wide arsenal of methods used to analyze neuronal activity. The most commonly used tests in research of behavioral plasticity are shock avoidance associated with chemosensory cues and courtship suppression after mating failure. Many authors emphasize the value of courtship suppression as a model of behavior most appropriate to natural conditions. However, researchers often investigate courtship suppression using immobilized and decapitated females as targets of courtship by males, which makes the data obtained from such flies less valuable. In our study, we evaluate courtship suppression towards immature mobile non-receptive females after training with mated or immature females combined with an aversive stimulus (quinine). We have shown that the previously described mechanisms of courtship suppression, as a result of the association of the courtship object with the repellent, as well as due to increased sensitivity to the anti-aphrodisiac cVA after mating failure, are not confirmed when immature mobile females are used. We discuss the reasons for the discrepancies between our results and literature data, define the conditions to be met in the courtship suppression test if the aim is to analyze the natural forms of behavioral plasticity, and present data on the test modifications to approximate conditions to natural ones.