An evolutionary step ahead: developing synthetic immunity against plant-parasitic nematodes

PhD project strategic theme: Bioscience for sustainable agriculture and food

Plant-parasitic nematodes threaten global food security and account for over 10% of the annual life-sustaining crop losses. The aim of my PhD is to develop a synthetic immune response against plant-parasitic nematode infection as a new tool to mitigate these losses.

Plant pathogens are an increasing concern for global food security. Extensive use of monoculture has led to increased populations of pests, including plant-parasitic nematodes. Much research is focussed on finding and generating resistant crops. As part of the evolutionary arms-race with their host, plant-parasitic nematodes have evolved various strategies to evade and/or nullify the existing plant immune system (e.g. "effectors"). To get a step ahead in the arms-race, and increase the robustness of resistance we need an immune system that these parasites have not co-evolved with.

The project will focus on the cyst nematode Heterodera schachtii, a sedentary endo-parasite that burrows into the root and parasitises a single cell. By regulating plant cell gene expression, it causes the host cell to re-differentiate into a syncytial feeding site. Once established, the survival of the nematode is dependent on this single cell: death of the cell means death of the nematode.

Based on preliminary data of nematode infection we hypothesise that there is a unique transcriptional expression pattern associated with the formation of this feeding-site. We aim to utilise this unique pattern as a 'fingerprint' for nematode infection to drive circuits for selective cell death.

The power of H. schachtii for testing these logic circuits lie in the ability to infect Arabidopsis thaliana in sterile tissue culture. This allows for rapid screening of circuits as genetic tools in this plant model are refined.

To design and build synthetic immunity we need to investigate, understand and create the following:

i) Refine the current dataset of H. schachtii infection for genes that uniquely describes feeding site formation in A. thaliana. ii) combining the dataset from objective i, with the extensive resources available for A. thaliana, identify, validate, and test promotor parts that are driven by nematode infection.; iii) construct synthetic logic circuits in A. thaliana using Boolean logic operators to detect nematode infection; and iv) Ultimately, utilise synthetic logic circuits to initiate programmed cell death and thus kill the nematode.

In summary, my PhD aims to increase knowledge on the regulation of host genes which lie in the core of cyst nematode feeding site formation, use this knowledge to develop a more flexible immune system, and ultimately provide a proof-of-principle that could be applied to other plant diseases.