Evolution of mosquito odour space

Many mosquito behaviours affect how dangerous females are as disease vectors. Clearly, finding people to bite is important for disease transmission, but so is, for example, sugar-feeding from flowers, which provides the energy to successfully host seek, and selecting a productive egg laying site, which guarantees a healthy next generation of disease vectors. This ability of mosquitoes to select resources is primarily odour mediated. Therefore, there is a fundamental need to understand the odour space inhabited by female mosquitoes. Understanding how that odour space differs among sympatric, closely related species, will give us insights into the evolution of odour space, which we currently know very little about. Additionally, it will provide practical knowledge that will help us predict future shifts in the odour space of these disease vectors and identify targets for future vector control initiatives. 

The purpose of this study is to describe the genetic mechanism that links the basic molecular building blocks of the peripheral olfactory system, the odorant receptors, with the ‘inherent’ odour-driven preferences displayed by sibling malaria mosquito species. 

We aim to describe the natural odour space of malaria mosquitoes, and assess its variation across three sibling species that display different innate resource preferences, in order to identify and assess the molecular mechanisms involved in actualising these different preferences. To this end, we will deorphanize the odorant receptors of adult female Anopheles gambiae with behaviourally active odorants that describe the natural odour space of this mosquito. We will then investigate the genotypic differences among three sibling species of malaria mosquitoes. Such differences may result in minor changes in odorant receptor structure that alters their functional identity in response to ecologically-relevant odours. To investigate the mechanism underlying such functional changes, we aim to systematically mutate each relevant polymorphism of select Ors, then assess their responses to odorants from the natural odour space. In addition, we will assess the effect of dynamic chemosensory gene expression on the differences described in the malaria mosquito odour space of these sibling species. 

This project is of significance because it builds on a strong foundation of extant but disparate behavioural, electrophysiological and molecular data on this system, which, when combined in this context, has the potential to unravel the molecular genetic basis of the evolution of malaria mosquito odour space.