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Doctoral thesis, 2017

Neuropeptidergic regulation of mosquito host-seeking behaviour

Christ, Peter

Abstract

Mosquitoes are vectors of numerous pathogens that cause human diseases, putting more than half of the world’s population at risk. These diseases are transmitted when a mosquito takes a blood meal following the successful seeking of a human host. Hostseeking is highly state dependent and predominantly mediated by olfactory cues. The goal of this thesis is to describe the neuropeptidergic regulation of the state dependent odour-mediated host-seeking behaviour. In order to identify and characterize the neuropeptides that are modulated by feeding and are involved in host-seeking, I analysed the antennal lobes, the primary olfactory centre, of Aedes aegypti, using semi-quantitative MALDI-TOF mass spectrometry. Functional evidence for the involvement of the identified neuropeptides in the regulation of host-seeking was provided using neuropeptide injections. I demonstrated that short neuropeptide F-2 (sNPF-2) and allatostatin-A-5 (AstA-5) are regulated upon blood feeding and that the injection of a binary mix of sNPF-2 and AstA-5 inhibited host-seeking in non-blood fed mosquitoes, mimicking the effect of a blood meal. I next characterized the sNPF and AstA receptors (sNPFR and AstAR) from Ae. aegypti and two other important disease vectors, Culex quinquefasciatus and Anopheles coluzzii assessing the receptor conservation and function as well as the regulation of the receptors in response to blood feeding. Within the AstA signalling system, I described a dipteran-specific duplication of the AstARs (R1 and R2) in mosquitoes. Functional characterization revealed that the AstAR2s show a higher sensitivity to AstAs compared to AstAR1s in the culicine mosquitoes Ae.aegypti and Cx. quinquefasciatus. In contrast, both AstARs in An. coluzzii showed a similar sensitivity to the AstA ligands, which suggests a divergence in the AstA signalling in mosquitoes. This is in contrast to the sNPFRs in the three species, which showed a high conservation in structure and receptor sensitivity. Blood feeding results in a selective regulation of transcript abundance of the more sensitive AstAR2 and the sNPFR in Cx. quinquefasciatus, but not in Ae. aegypti or An. coluzzii. This is indicative of differences in the regulatory mechanisms for AstA and sNPF in Cx. quinquefasciatus compared with the other species. In this thesis, I provide strong evidence that host-seeking is regulated by complex mechanisms involving at least two neuropeptidergic systems. These findings may shed new light on previous results and should encourage further investigation of other neuropeptide families. The functional characterization of the AstA and sNPF receptors leads to a better understanding of the conservation and regulation of neuropeptide signalling system and provides new targets for future research.

Keywords

olfaction,, modulation,, neuropeptides,, short neuropeptide F, allatostatin-A, host-seeking, sugar feeding, behaviour, G protein coupled receptors

Published in

Acta Universitatis Agriculturae Sueciae
2017, number: 2017:96
ISBN: 978-91-7760-082-4, eISBN: 978-91-7760-083-1
Publisher: Department of Plant Protection Biology, Swedish University of Agricultural Sciences

Authors' information

Christ, Peter
Swedish University of Agricultural Sciences, Department of Plant Protection Biology

UKÄ Subject classification

Behavioral Sciences Biology
Biochemistry and Molecular Biology
Other Biological Topics

URI (permanent link to this page)

https://res.slu.se/id/publ/104136