Slug viruses for biocontrol, and antiviral immunity in gastropods”

Supervisors: Darren J. Obbard, Dr Andy Evans

Project description:

Slugs are a perennial problem in crops across the arable and horticultural sector. Crops such as oilseed rape (up to 59% of the UK cropping area) and wheat (up to 22%) are significantly affected by slugs. The AHDB estimates that untreated, slug damage would cause losses in oilseed rape of £18M pa, £25.5M in wheat, and £53M in potatoes. Even with molluscicides, the loss to slugs in vegetables is estimated to be upwards of £8M a year. Approaches for slug management have not progressed appreciably since the introduction of molluscicide pellets several decades ago. However, these are now being revoked (methiocarb in 2015), or are under threat (due to metaldehyde contamination of drinking water catchments). Consequently, novel approaches for integrated slug management are required to safeguard metaldehyde for future use, and to utilise other available options. A biological control method that is suitable for integrated pest management is therefore highly desirable. 

Viruses have been successfully used to control insect pests. However, they have not been explored or advocated for the control of molluscs. In part, this may reflect the general lack of basic research in mollusc virology, pathology, and immunity – at least as compared with insects. 

However, advances in virus discovery are revolutionising our understanding of the viral diversity of molluscs, and provide an exciting opportunity to reassess viruses as a potential agent for mollusc control and to better understand their antiviral immune system. This proposal will use metagenomic sequencing to identify viruses naturally infecting wild slugs. To demonstrate active virus replication, we will use metagenomic sequencing of small RNAs. 

As the antiviral immune system of gastropods is little studied, we will capitalise on these data to elucidate the relative roles of antiviral RNAi (reported in a gastropod recently by the Obbard lab) and an interferon-like response (which has been reported for bivalve molluscs). We will do this by analysing RNAseq and small RNA expression patterns from wild slugs, and from slugs experimentally challenged with a poly-I:C immune elicitor. In parallel, we will attempt to isolate at least one virus by gradient centrifugation, and characterise its pathology. In combination, the approaches will (i) characterise the virus community of a pest slug species, (ii) generate fundamental information on the antiviral immune responses of that species, and (iii) potentially isolate viruses for future experimental work and/or development as biocontrol agents.

This project would suit anyone with an interest and background in virology, virus diversity, or innate immune mechanisms.