The evolution of prey-selectivity for snake venom neurotoxins, and the parallel evolution of neurotoxin resistance in prey

This Earmarked Scholarship project is aligned with a recently awarded Category 1 research grant. It offers you the opportunity to work with leading researchers and contribute to large projects of national significance.

Supervisor – Associate Professor Bryan

Venom is a dynamic evolutionary trait that have underpinned the explosive radiation of the advanced snakes. The ability to block nerve impulses from triggering muscle contraction is an efficient way in which to subjugate prey items. This project will use a world-class biomolecular interaction facility, which has at its core the only Octet HTX in the Southern Hemisphere, to investigate what amino acids in the nerve receptors of prey animals are selectively targeted by snake venoms in a taxon-specific manner. For example, we have shown that the king cobra, which specialises in feeding on other snakes, has a venom that is highly selective for the post-synaptic nicotinic acetylcholine receptors of the colubrid snakes upon which it feeds, and is dramatically much less potent upon non-prey animals like rats.

As there are several key amino acid variations between snake and rodent nicotinics, the testing of the venom against native nicotinics and mutated versions where a snake specific amino acid is swapped into a rodent receptor and testing undertaken to ascertain if such a swap increases sensitivity. With each difference tested one-by-one in such a systematic way, the identificatoin of the snake-specific particular amino acids selectively bound by king cobra venom can be elucidated. Similarly, we have shown that the venoms of snakes in the genus Aspidelaps and Elapsoidea are both highly selective for lizards. As these two genera are not each others closest relatives, this is due to a functional convergence between them.

In a similar manner as for the king cobra, by comparing lizard versus rodent, the particular amino acids selectively bound can be ascertained, and a determination made whether Aspidelaps and Elapsoidea have not only functionally converged in evolved lizard-specific venoms, but if there is also if there is a molecular convergence whereby the same amino acids in the lizard nicotinics have been targeted in a 'the target selects the toxins' manner. Other projects will examine the evolution of resistance in prey. For example, we have shown that of all the lizards tested so far, the Australian Eastern bearded dragon is unique in being almost totally resistant to snake venom neurotoxins. As these lizards are slow moving, they are highly vulnerable to predatory snakes. In contrast, we have shown that fast moving relatives like the Gilbert's dragon lizard are not resistant, which is consistent with their greater ability to escape relative to bearded dragons.

For this part of the PhD, the student would extract DNA from the lineages intervening between Gilbert's and bearded dragons, as well as additional species of bearded dragon to determine when this form of resistance evolved. Is it found in all bearded dragons? Is it found only in bearded dragons? Or do related genera such as Rankinia (eg mountain heath dragon (Rankinia diemensis)) share this trait?

Preferred educational background

Applications will be judged on a competitive basis taking into account the applicant's previous academic record, publication record, honours and awards, and employment history.

A working knowledge of evolutionary biology would be of benefit to someone working on this project.

A background or knowledge of biochemistry and molecular biology is highly desirable.

*The successful candidate must commence by Research Quarter 1, 2022. You should apply at least 3 months prior to the research quarter commencement date. International applicants may need to apply much earlier for visa reasons.

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