Biology subjects

Monsempes, C.

Publications and source records attributed to Monsempes, C..

4 recordsLinked to original sources

bioRxiv2026

Diversity of pheromone temporal coding disruptions by plant volatiles

Moth pheromone-sensitive olfactory receptor neurons (Phe-ORNs) encode the intermittent structure of pheromone plumes through precisely timed spikes, a mechanism that is essential for odor plume tracking behavior in flying insects. However, natural olfactory scenes are composed of diverse volatile plant compounds (VPCs) with complex temporal dynamics whose effects on pheromone signal intermittency encoding remain unclear. Two lines of research, encoding of pheromone intermittency and background interference, remain largely disconnected. Here, we performed electrophysiological recordings from moth Phe-ORNs to quantify their responses to turbulent plume-like flickering pheromone stimuli in constant or fluctuating backgrounds of a diversity of VPCs. We found that some VPCs reversibly disrupted the temporal coding of various subregions of the pheromone stimulus and the trial-to-trial variability. While Phe-ORN activation by VPCs partially accounted for the decrease in coding performance, Phe-ORN gain reduction was insufficient to explain the full extent of the disruption. Some VPCs disrupt temporal coding without activating Phe-ORNs, and others activate Phe-ORNs without altering temporal coding. A continuous background noise can induce strong adaptation and limit dynamic range, whereas a fluctuating background can interfere with pheromone pulse encoding by disrupting spike timing. Altogether, these results indicate that the pheromone detection system must contend with multiple forms of background noise rather than a uniform disturbance. Timing is key for olfactory navigation, and our results raise questions regarding how downstream circuits would process noisy sensory inputs. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=196 SRC="FIGDIR/small/713794v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@1c44fb6org.highwire.dtl.DTLVardef@14d5982org.highwire.dtl.DTLVardef@12f94a2org.highwire.dtl.DTLVardef@c731ee_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2021

Spodoptera littoralis genome mining brings insights on the dynamic of expansion of gustatory receptors in polyphagous noctuidae

The bitter taste, triggered via gustatory receptors, serves as an important natural defense against the ingestion of poisonous foods in animals, and the diversity of food diet is usually linked to an increase in the number of gustatory receptor genes. This has been especially observed in polyphagous insect species, such as noctuid species from the Spodoptera genus. However, the dynamic and physical mechanisms leading to these gene expansions and the evolutionary pressures behind them remain elusive. Among major drivers of genome dynamics are the transposable elements but, surprisingly, their potential role in insect gustatory receptors expansion has not been considered yet. In this work, we hypothesized that transposable elements and possibly positive selection would be involved in the active dynamic of gustatory receptor evolution in Spodoptera spp. We first sequenced de novo the full 465Mb genome of S. littoralis, and manually annotated all chemosensory genes, including a large repertoire of 373 gustatory receptor genes (including 19 pseudogenes). We also improved the completeness of S. frugiperda and S. litura gustatory receptor repertoires. Then, we annotated transposable elements and revealed that a particular category of class I retrotransposons, the SINE transposons, was significantly enriched in the vicinity of gustatory receptor gene clusters, suggesting a transposon-mediated mechanism for the formation of these clusters. Selection pressure analyses indicated that positive selection within the gustatory receptor gene family is cryptic, only 7 receptors being identified as positively selected. Altogether, our data provide a new good quality Spodoptera genome, pinpoint interesting gustatory receptor candidates for further functional studies and bring valuable genomic information on the mechanisms of gustatory receptor expansions in polyphagous insect species.

genomics↗

bioRxiv2019

A novel lineage of candidate pheromone receptors for sex communication in moths

Sex pheromone receptors (PRs) are key players in chemical communication between mating partners in insects. In the highly diversified insect order Lepidoptera, male PRs tuned to female-emitted type I pheromones (which make up the vast majority of pheromones identified) form a dedicated subfamily of odorant receptors (ORs). Here, using a combination of heterologous expression and in vivo genome editing methods, we bring functional evidence that at least one moth PR does not belong to this subfamily but to a distantly related OR lineage. This PR, identified in the cotton leafworm Spodoptera littoralis, is over-expressed in male antennae and is specifically tuned to the major sex pheromone component emitted by females. Together with a comprehensive phylogenetic analysis of moth ORs, our functional data suggest two independent apparitions of PRs tuned to type I pheromones in Lepidoptera, opening up a new path for studying the evolution of moth pheromone communication.

evolutionary biology↗

bioRxiv2017

Olfactory coding in the turbulent realm

Long-distance olfactory search behaviors depend on odor detection dynamics. Due to turbulence, olfactory signals travel as bursts of variable concentration and spacing and are characterized by long-tail distributions of odor/no-odor events, challenging the computing capacities of olfactory systems. How animals encode complex olfactory scenes to track the plume far from the source remains unclear. Here we focus on the coding of the plume temporal dynamics in moths. We compare responses of olfactory receptor neurons (ORNs) and antennal lobe projection neurons (PNs) to sequences of pheromone stimuli either with white-noise patterns or with realistic turbulent temporal structures simulating a large range of distances (8 to 64 m) from the odor source. For the first time, we analyze what information is extracted by the olfactory system at large distances from the source. Neuronal responses are analyzed using linear-nonlinear models fitted with white-noise stimuli and used for predicting responses to turbulent stimuli. We found that neuronal firing rate is less correlated with the dynamic odor time course when distance to the source increases because of improper coding during long odor and no-odor events that characterize large distances. Rapid adaptation during long puffs does not preclude however the detection of puff transitions in PNs. Individual PNs but not individual ORNs encode the onset and offset of odor puffs for any temporal structure of stimuli. A higher spontaneous firing rate coupled to an inhibition phase at the end of PN responses contributes to this coding property. This allows PNs to decode the temporal structure of the odor plume at any distance to the source, an essential piece of information moths can use in their tracking behavior.\n\nAuthor SummaryLong-distance olfactory search is a difficult task because atmospheric turbulence erases global gradients and makes the plume discontinuous. The dynamics of odor detections is the sole information about the position of the source. Male moths successfully track female pheromone plumes at large distances. Here we show that the moth olfactory system encodes olfactory scenes simulating variable distances from the odor source by characterizing puff onsets and offsets. A single projection neuron is sufficient to provide an accurate representation of the dynamic pheromone time course at any distance to the source while this information seems to be encoded at the population level in olfactory receptor neurons.

neuroscience↗