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Doctoral thesis, 2020

Chemosensation in Aedes aegypti: from molecular response profiles to host-seeking behaviour

Tallon, Anaïs

Abstract

The female mosquito Aedes aegypti is the primary urban vector of various highly infectious neglected tropical diseases. Disease transmission relies heavily on odourmediated behaviours, including e.g., sugar- and host-seeking, which are crucial during the mosquito life cycle and has dire impacts on vectorial capacity. Olfaction is, one of the most sophisticated sensory systems, and is the sense by which insects locate and discriminate biologically-relevant odorant volatiles. In female mosquitoes, host-seeking is generally not observed before 2-3 days following adult emergence. Of note, males have also been shown to respond to and orient towards host-associated cues. Vector-borne pathogens can alter the behaviour and physiology of their host, consequently increasing the risk of disease transmission. Thus, the modulation of host-seeking depends on multiple factors, including e.g., age, sex, and infection by a pathogen, which is the main focus of this thesis. During my PhD, I have shown that the modulation of the onset of host-seeking coincides with changes in transcript abundance of chemosensory-related genes expressed in the antennae of newly-emerged mosquitoes. Of these genes, one particular odorant receptor, OR117, exhibits a decrease in transcript abundance as female mosquitoes become capable of host-seeking. Later, I have functionally characterised OR117, together with another odorant receptor-of-interest, OR103, which has previously been shown to be more abundant in the human-preferring subspecies of Ae. aegypti. Both OR117 and OR03 are tuned to monoterpenes, and their potential role in the transition between sugar- to host-seeking and human avoidance, respectively, is discussed. Furthermore, I have demonstrated that the locomotion and host-seeking is modulated in dengue-infected females in a time-dependent manner, i.e. depending on the time post-infection, and coincides with changes in transcript abundance of genes involved in neural signalling pathways. A better understanding of the modulation of odour-mediated behaviours in mosquitoes is crucial for the development of efficient control strategies against disease vector control.

Keywords

chemical ecology; chemosensory-related genes; dengue; deorphanization; electrophysiology; heterologous expression; mosquitoes; olfaction

Published in

Acta Universitatis Agriculturae Sueciae
2020, number: 2020:44
ISBN: 978-91-7760-606-2, eISBN: 978-91-7760-607-9
Publisher: Department of Plant Protection Biology, Swedish University of Agricultural Sciences

Authors' information

Tallon, Anaïs
Swedish University of Agricultural Sciences, Department of Plant Protection Biology

UKÄ Subject classification

Other Biological Topics
Behavioral Sciences Biology

URI (permanent link to this page)

https://res.slu.se/id/publ/107039