Biology subjects

Pal Mahadevan, V.

Publications and source records attributed to Pal Mahadevan, V..

5 recordsLinked to original sources

bioRxiv2026

Conserved odor detection and divergent behavioral valence in ecologically distinct drosophilid flies

Competition among living organisms often drives selection for the exploitation of new ecological niches. Successfully colonizing these niches requires the evolution of specialized physiological adaptations. In drosophilid flies, which depend heavily on their sense of smell, such adaptations frequently involve the modification of specific olfactory circuits to detect and respond to niche-defining odorants. Although evolutionary patterns within the Sophophora subgenus have been studied to a great extent, the peripheral circuit evolution, as well as the extent to which the peripheral code is conserved in other subgenera, remains poorly understood. Here, I compared the antennal basiconic olfactory coding patterns in D. melanogaster, D. virilis and D. busckii, belonging to the subgenera Sophophora, Drosophila and Dorsilopha, respectively. Despite their substantial evolutionary divergence ([~]40 Mya), I found partial conservation of basiconic peripheral coding, together with several strongly conserved ligand responses across species. I then tested whether conserved peripheral detection also corresponds to conserved behavioral valence. These experiments revealed that species can exhibit divergent behavioral responses to the same ligand, even when peripheral detection is conserved. Finally, I describe four individual cases of circuit evolution across selected species pairs, providing independent case studies of peripheral olfactory evolution.

evolutionary biology↗

bioRxiv2024

Preference for and resistance to a toxic sulfur volatile opens up a unique niche in Drosophila busckii

The ability to tolerate otherwise toxic compounds can open up unique niches in nature. Among drosophilid flies few examples of such adaptations are known and then typically from highly host specific species. Here we show that the human commensal Drosophila busckii uses dimethyldisulfide (DMDS) as a key mediator in its host selection. Despite DMDSs neurotoxic properties1, D. busckii has evolved tolerance towards high concentrations and uses the compound as an olfactory cue to pinpoint food and oviposition sites. This adaptability is likely linked to an insensitive cytochrome c oxidase (COX), a DMDS target in other insects. Our findings position D. busckii as a potential model for studying resistance to toxic gases affecting COX and offer valuable insights into evolutionary adaptations within specific ecological contexts.

ecology↗

bioRxiv2023

Temperature-dependent modulation of odor-dependent behavior in three drosophilid fly species of differing thermal preference

Rapid and ongoing climate change increases global temperature and impacts both feeding and reproduction in insects. The sense of smell plays an important underlying role in these behaviors in most insect species. Here, we aimed to investigate how changing temperatures affect odor detection and ensuing behavior in three drosophilid flies: Drosophila novamexicana, D. virilis and D. ezoana, species that have adapted to life in desert, global and subarctic climates, respectively. Using a series of thermal preference assays, we confirmed that the three species indeed exhibit distinct temperature preferences. Next, using single sensillum recording technique, we classified olfactory sensory neurons (OSNs) present in basiconic sensilla on the antenna of the three species and thereby identified ligands for each OSN type. In a series of trap assays we proceeded to establish the behavioral valence of the best ligands and chose guaiacol, methyl salicylate and isopropyl benzoate as representatives of a repellent, attractant and neutral odor. Next, we assessed the behavioral valence of these three odors in all three species across a thermal range (10-35 C), with flies reared at 18{degrees}C and 25{degrees}C. We found that both developmental and experimental temperatures affected the behavioral performance of the flies. Our study thus reveals temperature-dependent changes in odor-guided behavior in drosophilid flies.

ecology↗

bioRxiv2021

Response plasticity of Drosophila olfactory sensory neurons

In insect olfaction, sensitization refers to the amplification of a weak olfactory signal when the stimulus is repeated within a specific time window. In the vinegar fly, Drosophila melanogaster, his occurs already at the periphery, at the level of olfactory sensory neurons (OSNs) located in the antenna. In our study, we investigate whether sensitization is a widespread property in a set of seven types of OSNs, as well as the mechanisms involved. First, we characterize and compare differences in spontaneous activity, response velocity and response dynamics among the selected OSN types. These express different receptors with distinct tuning properties and behavioral relevance. Second, we show that sensitization is not a general property. Among our selected OSNs types, it occurs in those responding to more general food odors, while OSNs involved in very specific detection of highly specific ecological cues like pheromones and warning signals show no sensitization. Moreover, we show that mitochondria play an active role in sensitization by contributing to the increase in intracellular Ca2+ upon weak receptor activation. Thus, by using a combination of single sensillum recordings (SSR), calcium imaging and pharmacology, we widen the understanding of how the olfactory signal is processed at the periphery. O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

neuroscience↗

bioRxiv2021

Functional interaction between Drosophila olfactory sensory neurons and their support cells

Insects detect volatile chemicals using antennae, which house a vast variety of olfactory sensory neurons (OSNs) that innervate hair-like structures called sensilla where odor detection takes place. In addition to OSNs, the antenna also hosts various support cell types. These include the triad of trichogen, tormogen and thecogen support cells that lie adjacent to their respective OSNs. The arrangement of OSN supporting cells occurs stereotypically for all sensilla and is widely conserved in evolution. While insect chemosensory neurons have received considerable attention, little is known about the functional significance of the cells that support them. For instance, it remains unknown whether support cells play an active role in odor detection, or only passively contribute to homeostasis, e.g. by maintaining sensillum lymph composition. To investigate the functional interaction between OSNs and support cells, we used optical and electrophysiological approaches in Drosophila. First, we characterized the distribution of various supporting cells using genetic markers. By means of an ex vivo antennal preparation and genetically-encoded Ca2+ and K+ indicators, we then studied the activation of these auxiliary cells during odor presentation in adult flies. We observed acute responses and distinct differences in Ca2+ and K+ fluxes between support cell types. Finally, we observed alterations in OSN responses upon thecogen cell ablation in mature adults. Upon inducible ablation of thecogen cells, we notice a gain in mechanical responsiveness to mechanical stimulations during single-sensillum recording, but a lack of change to neuronal resting activity. Taken together, these results demonstrate that support cells play a more active and responsive role during odor processing than previously thought. Our observations thus reveal that support cells functionally interact with OSNs and may be important for the extraordinary ability of insect olfactory systems to dynamically and sensitively discriminate between odors in the turbulent sensory landscape of insect flight.

neuroscience↗