Evolution of the olfactory code in the Drosophila melanogaster subgroup

Area of Science:

• Evolutionary biology
• Neuroscience
• Genomics

Background:

• The Drosophila melanogaster subgroup comprises nine closely related species, offering a model for evolutionary studies.
• Understanding olfactory code evolution is crucial for deciphering species-specific adaptations and behaviors.

Purpose of the Study:

• To investigate the evolutionary trajectory of the olfactory code across nine sister species within the Drosophila melanogaster subgroup.
• To identify specific changes in olfactory receptor neuron (ORN) ligand affinity and tuning profiles.

Main Methods:

• In vivo electrophysiological measurements, specifically single-cell recordings, were employed.
• Ligand affinity of a defined subset of olfactory receptor neurons (ORNs) was measured across all nine species.

Main Results:

• The olfactory code, as relayed by the studied ORNs, demonstrates a high degree of conservation across the species.
• Distinct evolutionary shifts were observed within the simulans clade, characterized by altered tuning profiles of specific ORN types.
• A more drastic olfactory alteration in D. sechellia involved a sensillum type replacement, potentially linked to its specific host plant.

Conclusions:

• The olfactory system in the Drosophila melanogaster subgroup is largely conserved, despite variations in distribution and host preference.
• Specific evolutionary adaptations in the olfactory code, particularly in D. sechellia, may be driven by host-specific pressures.
• The study highlights the interplay between olfactory system evolution and ecological specialization.