George Wang Rose Hills
Chemosensory Adaptation to Host Specialization in Herbivorous Drosophilidae
Herbivory is a key innovation that accounts for half of all insects and one-third of all living orders. It is believed that loss-of-function in chemoreceptor genes is the driving force behind the transition to herbivory in insects, but the underlying mechanisms are still poorly understood. One such chemoreceptor gene within the ionotropic receptor (IR) family, IR92a, mediates behavioral attraction of amines in microbe-feeding flies and mosquitoes through a population of olfactory sensory neurons (OSNs). I will investigate the hypothesis that in herbivorous flies, this chemoreceptor protein has diminished sensitivity toward amines, and that the number of OSNs expressing this chemoreceptor is lower than in microbe-feeding flies, due to olfactory specializations that entail greater emphasis on the detection of volatiles from living plants rather than on by-products of fermentation. Understanding whether S. flava has decreased sensitivity to volatile amines will shed light onto how the losses of chemosensory genes sensitive to these compounds have played a role in a major ecological transition, from microbe-feeding to herbivory, in insects.