Genèse de l’Observatoire du Patrimoine et de la Culture Scientifiques et Techniques

L’OCIM a reçu une nouvelle mission : celle d’un Observatoire du Patrimoine et de la Culture Scientifiques et Techniques. Partant d’une interrogation sur la définition d’un observatoire, cet article présente les premières réflexions et pistes de travail qui animent la gestation de ce nouveau dispositif, au service des acteurs de ce champ spécifique.L’OCIM has been doted with a new mission: that of being a Heritage and Scientific Culture Observatory. Stemming from a wish to define what an observatory is, this article presents the initial ideas and ways to advance with the new entity that is available to all actors within this specific field through its gestation process

An Inhibitory Sex Pheromone Tastes Bitter for Drosophila Males

Sexual behavior requires animals to distinguish between the sexes and to respond appropriately to each of them. In Drosophila melanogaster, as in many insects, cuticular hydrocarbons are thought to be involved in sex recognition and in mating behavior, but there is no direct neuronal evidence of their pheromonal effect. Using behavioral and electrophysiological measures of responses to natural and synthetic compounds, we show that Z-7-tricosene, a Drosophila male cuticular hydrocarbon, acts as a sex pheromone and inhibits male-male courtship. These data provide the first direct demonstration that an insect cuticular hydrocarbon is detected as a sex pheromone. Intriguingly, we show that a particular type of gustatory neurons of the labial palps respond both to Z-7-tricosene and to bitter stimuli. Cross-adaptation between Z-7-tricosene and bitter stimuli further indicates that these two very different substances are processed by the same neural pathways. Furthermore, the two substances induced similar behavioral responses both in courtship and feeding tests. We conclude that the inhibitory pheromone tastes bitter to the fly

Analyse génétique de la réponse gustative aux phéromones sexuelles et aux substances amères chez Drosophila melanogaster

DIJON-BU Sciences Economie (212312102) / SudocSudocFranceF

Taste discrimination of pheromones in Drosophila

1095-6433 doi: DOI: 10.1016/j.cbpa.2007.01.15

Is mate choice in Drosophila males guided by olfactory or gustatory pheromones?

International audienceDrosophila melanogaster flies use both olfactory and taste systems to detect sex pheromones and select the most suitable mate for reproduction. In nature, flies often face multiple potential partners and should have an acute sensory ability to discriminate between different pheromonal bouquets. We investigated both the pheromones and the chemosensory neurons influencing Drosophila mate choice. We measured various courtship traits in single tester males simultaneously presented with two target male and/or female flies carrying different pheromonal bouquets (pairs of control flies of the same or different sex, same-sex target pairs of pheromonal variant strains). The courtship traits reflected the perception of either olfactory cues perceived before or gustatory cues perceived after the first physical taste contact. Our results suggest that male mate choice exists in D. melanogaster and that male discrimination between potential mates could be a two-step process involving chemical cues perceived before and after the first gustatory contact. In addition, when a male was simultaneously presented with two potential sexual partners, the olfactory and gustatory cues he used depended on the pheromonal patterns of both flies, but his response could also depend on additional effects resulting from the simultaneous perception of the two flies, leading to a nonlinear choice of a sexual partner. Moreover, some tester males with genetically altered gustatory receptor neurons strongly changed their partner preference, indicating that the fly's peripheral nervous system is essential for pheromonal detection and mate choice

Feminization and Alteration of Drosophila Taste Neurons Induce Reciprocal Effects on Male Avoidance Behavior

0001-8244 (Print) 1573-3297 (Online)Taste perception allows most animals to find edible food, potential mates, and avoid ingesting toxic molecules. Intriguingly, a small group of Drosophila taste neurones (expressing Gr66a-Gal4) involved in the perception of bitter substances is also used to detect 7-tricosene (7-T), a male cuticular pheromone. Male flies tend to be inhibited by 7-T whereas females are stimulated by this pheromone. To better understand their role on male courtship, Gr66a-Gal4 neurons were genetically feminized or altered with various transgenes, and the response of transgenic males was measured toward live targets carrying various amounts of 7-T, or of bitter molecules (caffeine, quinine and berberine). Surprisingly, tester males with feminized taste neurons showed an increased dose-dependent avoidance toward targets with high level of any of these substances, compared to other tester males. Conversely, males with altered neurons showed no, or very little avoidance. Moreover, the surgical ablation of the sensory appendages carrying these taste neurons differently affected the behavioral response of the various tester males. The fact that this manipulation did not affect the courtship toward control females nor the locomotor activity of tester males suggests that Gr66a-Gal4 neurons are involved in the sex-specific perception of molecules inducing male avoidance behavio

7-T elicits a dose-dependent electrophysiological response in a subset of labial palp gustatory neurons.

<p>(A) Schematic illustration of the “tungsten electrod method” which allows simultaneous but separate stimulation and recording of gustatory and pheromonal stimuli. The stimulus was contained in a glass microelectrode capping the tip of the sensillum; caffeine and 7-T were dissolved in mineral oil, sucrose and salts were dissolved in water. Recordings were obtained from three types of labellar sensilla (l-, i- and s-type) determined according to both their location and shape <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000661#pone.0000661-Shanbhag1" target="_blank">[21]</a>–<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000661#pone.0000661-Hiroi1" target="_blank">[23]</a> in wild-type Canton-S males. So far, we were unable to use this method to record from sensilla on the fore-tarsus, because of the relative hardness of the leg cuticle and the slender form of this appendage. (B) In i-type sensilla, one cell responded to 10⁻⁸M 7-T, whereas the second cell responded to 0.2 M NaCl. The shaded bar represents the duration of the stimulation (2 sec). Elicited spikes were separated according to spike height (amplitude of “class 0” and “class 1” were 0.3–0.5 mV and 0.1–0.2 mV, respectively); see left side of panel; n = 20 flies. (C) Conversely, l-type sensilla responded normally to NaCl, sucrose, KCl but not to 10⁻⁸M 7-T. Recording were made in similar conditions as described for i-type sensilla; n = 32 flies. (D) 7-T responsive sensilla were mapped on the labial palp with tungsten electrode recordings. Both i- and s-types-but no l-type—sensilla responded to stimulation with 7-T (a sensillum was considered as responsive if it showed at least one response to 7-T among 2-5 trials). Anterior is up, dorsal is right. GRN = gustatory receptor neuron; MR = mechanoreceptor neuron. (E) In a s-type sensillum (S2), the L2 cell showed a dose-dependent increased activity to 7-T (between 10⁻¹² and 10⁻⁸M) while the L1 cells were not activated. Vertical axis: total number of spikes during 2 sec stimulation. Significantly increased activity of the L2 cell is indicated (a–b: <i>p</i><0.05, a–c: <i>p</i><0.01; n = 4–10).</p

7-T and caffeine both inhibit the proboscis extension reflex (PER) of male and female flies.

<p>Data indicate the PER frequency in male and female flies either unilaterally stimulated with 0.1M sucrose (empty bars), or bilaterally stimulated with 0.1M sucrose on one side and a test solution on the other side (filled bars). The test solution either consisted of 10⁻⁸M 7-T, or 0.1M caffeine (both dissolved in mineral oil), or mineral oil (tested only in males). Significant differences in PER between the two stimulation conditions were estimated for each treatment and sex by Chi2 with Yates' correction (*** : <i>p</i><0.001 ; * : <i>p</i><0.05). Each data set was obtained from 6–7 series of experiments with 70–90 flies except for caffeine (n = 22–30).</p

7-T and of bitter molecules dose-dependently inhibit male courtship.

<p>The intensity of courtship (CI) was measured in tester WT males (empty circles) and in <i>Gr66a-Gal4</i>/WT males (filled circles) paired with decapitated <i>desat1</i> target males covered either with pure 7-T or with one of the three bitter molecules—caffeine, quinine or berberine—as indicated below the curves. Each chemical to be tested was diluted in the appropriate solvent at a concentration adjusted to standardize the volume of solvent deposited on each object fly (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0000661#s4" target="_blank">Material and methods</a>). The solvents used here had no effect on male CI. The frequency of inhibition corresponds to the number of males with CI<44.1 (observed in the control situation between two WT males). For example, 50% inhibition indicates that 50% of the tester males showed a CI<44.1. n = 20–30.</p