Supervisors

Dr Mark Hanson University of Exeter, ESE, CEC
Dr Bartek Troczka University of Exeter, ESE, CEC
Prof Chris Bass University of Exeter, ESE, CEC

Location:

Centre for Ecology and Conservation, Penryn Campus, Cornwall

The University of Exeter’s Centre for Ecology and Conservation is inviting applications for a PhD studentship funded by the Faculty of Environment, Science and Economy to commence on 23 September 2024 or as soon as possible thereafter.  For eligible students the studentship will cover Home or International tuition fees plus an annual tax-free stipend of at least £19,237 for 3.5 years full-time, or pro rata for part-time study.  International applicants need to be aware that you will have to cover the cost of your student visa, healthcare surcharge and other costs of moving to the UK to do a PhD. The following project is one of four being advertised as part of a competitive process for funding, there is one award available.

Project keywords (up to 5): Innate immunity, Toll-like receptors, cGAS-STING, host-pathogen interaction, Lysozyme and antimicrobial peptide.

Project Background

It is projected the world must increase crop yield by 40% from current levels to feed the human population of 2050. Insect pests such as aphids are responsible for billions of dollars (USD) of damage. Aphids vector viral and microbial diseases, and directly damage crops. This problem demands effective biocontrol strategies, yet chemical insecticide use is increasingly discouraged. Segregating insecticide resistance also requires contingency strategies to handle pest species: in 2020, insecticide resistance in Green peach aphids (Myzus persicae) caused ~£67 million of economic losses to UK sugar beet agriculture alone. Similar economic threats unquestionably apply to crops attacked by other pest species. A promising strategy already being employed is the use of insect-infecting microbes that can be spread on crops.

Insect-pathogenic microbes have specific host ranges determined by the host immune system. Insect immunity has been extensively characterised in fruit flies, but also other species of holometabolous insects including flies, beetles, and moths. However, there is a considerable knowledge gap in relation to the aphid immune system, and hemipteran immune systems more generally. From what is known, aphids have many bacterial symbionts, some of which supplement their diet with essential nutrients. However, some facultative symbionts are known to protect aphids against infection by parasites. Perhaps as a consequence, the Green pea aphid Acyrthosiphon pisum, has lost the “Immune deficiency” (Imd) pathway conserved across insects (Gerardo et al., 2010; Genome Biology). Moreover, Green pea aphids succumb to infection easily, and lack critical bacteria-killing enzymatic activity in their blood. It’s thought aphids evolved loss of this immune pathway to avoid harming beneficial bacterial symbionts – however, this has never been formally scrutinized.

Recent advances in immune study have discovered an immensely under-appreciated complexity to host-pathogen interactions. First, beyond the RNA interference (RNAi) pathway, cGAS-STING was recently described as a core antiviral immune pathway of animals. In fruit flies, cGAS-STING relies on cross-talk with the Imd pathway. It’s therefore unclear if aphids are expected to retain cGAS-STING signalling given A. pisum has lost core elements of the Imd pathway. Moreover, it is now understood that host-symbiont interactions can rely largely on resilience of symbiotic bacteria to host immune responses, counter to the idea that hosts should evolve loss of immune defences to avoid disrupting symbionts.

It's therefore unclear if the findings of A. pisum regarding aphid immune evolution are the exception or the rule. It’s further unclear how aphid immunity might compare to other insects, particularly for cGAS-STING signalling critical to antiviral defence for which nothing is known in hemipterans. Presently, the broader aphid immune system is a black box. This project will characterise aphid immunity, and in doing so, improve the potential for deployment of insect pathogens as biocontrol agents. More fundamentally, it will also improve our understanding of insect humoral immunity, which has largely been neglected in aphids and their relatives of economic importance (e.g. bed bugs, bean bugs, kissing bugs).

Project Aims and Methods

This project will characterize the immune system of the Green peach aphid M. persicae. The student will screen newly-available aphid genomes, including from other species, to learn what are the core elements of the aphid immune system. The student may further utilise a living library of 110 sequenced M. persicae strains to screen for variation in immune genes with functional importance. The student will learn BLAST, annotation, genome comparative techniques, and phylogenetics.

To validate the aphid immune response functionally, the student will perform infections in aphids and fruit flies monitoring survival and core immune response genes. The student will further use molecular techniques (e.g. qPCR, RNAseq) and approaches to measure enzymatic or antimicrobial activity (fluorescence, growth kinetics, protein gels).

Student Experience
This project will be led by an interdisciplinary team with complementary expertise in insect immunity (MAH), molecular biology (BT), and aphid genetics and genomics (CB), providing a rich environment for learning. The student is encouraged to shape the study and its focal direction, and will gain experience across molecular biology, bioinformatics, genetics, innate immunity, and molecular evolution. These are skills highly valued in research and industry.

Candidate requirements
The candidate should be enthusiastic to work with insects, with some experience in any of the following categories: genetics, immunity, insect biology, bioinformatics and/or computer science. Applicants are encouraged to apply from a broad range of backgrounds.

Training
The candidate will receive training in relevant techniques from the supervisors. Further, the candidate will be supported with opportunities to attend relevant training workshops or inter-laboratory collaborative visit to develop skills and knowledge at the cutting edge. The candidate will further benefit from support for annual conference/meeting attendance, including one international conference over the course of their fellowship.

Useful links/Information
The candidate is encouraged to read more on the research of the supervisory team of Mark A. Hanson, Bartek Troczka and Chris Bass.

Entry requirements

Applicants for this studentship must have obtained, or be about to obtain, a First or Upper Second Class UK Honours degree, or the equivalent qualifications gained outside the UK, in an appropriate area of science or technology. 

If English is not your first language you will need to meet the required level as per our guidance at https://www.exeter.ac.uk/pg-research/apply/english/

How to apply

Apply now

In the application process you will be asked to upload several documents. 
• CV
• Letter of application (outlining your academic interests, prior research experience and reasons for wishing to undertake the project).
• Transcript(s) giving full details of subjects studied and grades/marks obtained (this should be an interim transcript if you are still studying)
• Names of two referees familiar with your academic work. You are not required to obtain references yourself. We will request references directly from your referees if you are shortlisted.
• If you are not a national of a majority English-speaking country you will need to submit evidence of your proficiency in English.

The closing date for applications is midnight on 29 July 2024. 

If you have any general enquiries about the application process please email PGRApplicants@exeter.ac.uk or phone 0300 555 60 60 (UK callers) +44 (0) 1392 723044 (EU/International callers)  Project-specific queries should be directed to the main supervisor.

Summary