Parasite mind control
My current research looks into how parasites control the behaviour of their hosts. Using transcriptomics we are investigating how terrestrial insects are manipulated to drown themselves in water. This fascinating host manipulation occurs in two systems, earwig/nematodes and wētā/hairworm. We are interested to know if the genetic interactions between parasites and hosts are similar between the two systems.
Fig. Host manipulation in Weta by a Nematomorpha parasite.
Battle of the body snatchers
In 2019 I was awarded a Marsden fast-start grant to investigate how parasites interact with each other inside their hosts. Well working on the parasite mind control project I noticed that a complication (for the hairworms at least) arises when, as is often the case, the host is infected by more than one hairworm. If any of these co-occurring hairworms have not yet developed enough to emerge, then they will die alongside the host when the mature hairworm successfully manipulates the host to seek water and drown itself. If these immature hairworm are to survive, they must work to sabotage and delay the host manipulations induced by mature hairworms. Alternatively, closely related hairworms found in the same host could sacrifice their own survival for that of a close relative (kin-selection).
A weta with hairworm emerging, image: Jean-François Doherty (PhD student Otago)
Diapause regulation in Rhagoletis pomonella and Rhagoletis cerasi
Diapause is a hormonally controlled seasonal response to environmental cues that results in developmental arrest, enabling arthropods to avoid unfavorable environmental conditions. Development and cell proliferation are halted during diapause until termination is triggered via environmental cues.
My previous research focuses on understanding how diapause regulation differs in two populations of two species of Rhagoletis flies. Using a large scale comparative transcriptomic dataset through winter pupal diapause we compared gene expression changes between populations that terminate diapause earlier (apple hosts R. pomonella, low altitude R. cerasi) to populations that terminate diapause later (haw hosts R. pomonella, high altitude R. cerasi). Previous work (PI Greg Ragland) showed that by the end of winter gene expression differences are already pronounced between R. pomonella populations that infest apple and haw hosts (Meyers et al 2016). By combining gene expression differences through winter (from diapause initiation to near diapause termination) and whole genome resequencing of early/late/average eclosers we have been able to build a clearer understanding of how diapause termination timing is controlled in early and late diapausing populations (Dowle et al 2020).
Dowle, EJ., Powell, THQ., Doellman, MM., Meyers, PJ., Calvert, MB., Walden, KKO., Robertson, HM., Berlocher, SH., Feder, JL., Hahn, DA., Ragland, GJ. Genome-wide variation and transcriptional changes in diverse developmental processes underlie the rapid evolution of seasonal adaptation. PNAS 2020 117 (38): 23960-23969
Meyers, PJ., Powell, THQ., Walden, KKO, Schieferecke, AJ., Feder, JL., Hahn, DA., Robertson HM., Berlocher, SH., Ragland, GJ. Divergence of the diapause transcriptome in apple maggot flies: winter regulation and post-winter transcriptional repression.