Identification of peptidergic markers in entomopathogenic nematodes for host-finding strategies

Insect pests pose a great threath to agriculture worldwide. About 10-16% of all crops is lost due to insect pests, which has an estimated yearly cost of 70 billion dollars. On top of this, due to the spreading of chemical pesticides in the environment, fresh water supplies and foods, there is an associated yearly health cost of nearly seven billion dollars. There is an increase in pesticide resistance among insects due to wide spread application and there is a need for more directed insect pest managment. A good solution to these problems would be to use biocontrol agents, of which entomopathogenic nematodes have a very high potential.

Entomopathogenic nematodes are small round worms, which may show a very high insect host specificity and have a very high killing rate of their insect hosts once infected. They are already being applied as biocontrol agents, but there is a need for new species that are adapted for new ecological niches and which have higher infection rates. To efficiently improve these aspects of entomopathogenic nematodes, it is the most interesting to look at host finding behaviour, and how this is regulated on a molecular level. This will lead to new possibilities, like breeding new strains, that can be more efficiently applied as biocontrol agents. Neuropeptides are very potent markers for following host finding behaviour during breeding programs, since they are very likely to have an important role in host finding behaviour regulation at a neuronal level.

In this doctorate, I aim to identify neuropeptides that regulate host finding behaviour. For this I will use mass spectrometry to analyse peptides from the entomopathogenic nematode Steinernema carpocapsae. First of all, I will optimise an extraction protocol for neuropeptides that is already applied in the very similar model organism Caenorhabditis elegans. Next, a reference peptidome can be compiled and differential peptidomics studies can be done. Different S. carpocapsae strains - showing different host finding behaviour strategies - will be analysed, leading to the identification of differentially expressed peptides with possible causal relations to the difference in host finding behaviour strategies. Finally, I will perform localisation and functional studies to confirm the roles and functions of these peptides in host finding behaviour.