Doctor Sharon Towett-Kirui

Candidature

Graduated PhD 2022

Thesis title

Molecular characterisation of the twisted wing endoparasitoid Dipterophagus daci (Strepsiptera) and its interactions with Wolbachia and multiple tephritid fruit fly host species

Research Project

Queensland fruit fly (Bactrocera tryoni) and several other Bactrocera species are recognized as the most significant horticultural pests and biosecurity threats in Australia. So far, pest management programmes have primarily relied on insecticides; however, several effective insecticides have recently been banned due to human and environmental health concerns. A successful strategy to control fruit fly is the Sterile Insect Technique (SIT) involving the release of irradiated males that mate with females in the field, effectively stopping their reproduction. However, irradiation damages the mating performance of irradiated males. An alternative to SIT is the Incompatible Insect Technique (IIT) using Wolbachia, and this strategy is currently used to successfully control mosquito populations in Australia and elsewhere.

Wolbachia is a maternally transmitted intracellular bacterium, Wolbachia is common in many insect species, and within its host can manipulate reproduction and affect host fitness. Opportunities to study Wolbachia – host interactions have not be exhausted given that Wolbachia prevalence varies in different insect species, and that its effect on the host is dependent on the Wolbachia strain and the specific host. My research will focus on the Wolbachia symbiosis of Queensland fruit fly (Bactrocera tryoni, Tephritidae), Australia’s most significant horticultural pest. This will entail characterisation of Wolbachia in field populations of Queensland fruit fly and related Australian tephritid species by looking at the temporal distribution of Wolbachia and whole genome sequencing of previously reported Wolbachia infections (Morrow et al., 2014; Morrow et al., 2015). Furthermore, I will utilise embryonic microinjection technique to establish a stable Wolbachia infection in B. tryoni and to test whether this pest species could be controlled by exploiting the reproductive sterility some strains of Wolbachia induce in incompatible crosses.

Findings from this study will shed some light on the relationship between Wolbachia and its host, a comprehensive characterization of Wolbachia infections in Australian fruit flies and hence underscore the possibility of applying Wolbachia in the control of B. tryoni and other fruit fly pests

Awards

Industrial Transformation Postgraduate Research Award, Western Sydney University, Australia
Swiss Nation Science Foundation /R. Geigy. Stiftung: International Centre for Insect Physiology and Ecology (ICIPE) Master Research Scholarship. Nairobi, Kenya
Internship Scholarship: Professor Bruno Lemaitre lab (3months): Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland
UNESCO MARS travel grant: UNESCO- Merck Africa Research Summit (MARS) 28th and 29th November 2016: Addis Ababa, Ethiopia

Supervisors

A/Pro. Markus Riegler, Dr. Jennifer Morrow, Dr. Toni Chapman

Publications

Towett-Kirui S, Morrow JL, Riegler M, (2022) 'Substantial rearrangements, single nucleotide frameshift deletion and low diversity in mitogenome of Wolbachia-infected strepsipteran endoparasitoid in comparison to its tephritid hosts', Scientific Reports, vol.12, Article no.477

Towett-Kirui S, Morrow JL, Close S, Royer JE, Riegler M, (2021) 'Host-endoparasitoid-endosymbiont relationships: concealed Strepsiptera provide new twist to Wolbachia in Australian tephritid fruit flies', Environmental Microbiology, vol.23, no.9, pp 5587–5604

Chepkemoi ST, Mararo E, Butungi H, Paredes J, Masiga D, Sinkins SP, Herren JK, (2017) 'Identification of Spiroplasma insolitum symbionts in Anopheles gambiae', Wellcome Open Research, (in press)