Characterisation of cue-dependent behaviour in plant parasitic nematodes (PPNs); the neurobiology of host plant invasion

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Understanding of C. elegans neurobiology will be leveraged to provide insight into the neural mechanisms underpinning host location by plant parasitic nematodes (PPN). We will develop new assays for measuring cue-dependent behaviour in two species of PPN. Preliminary assays indicate PPNs exhibit a similar repertoire of locomotory behaviours as C. elegans comprising reversals, turns, speed of motility, direction of motility, and in a similar fashion to C. elegans, these behaviours are modified by chemosensory cues. Thus we will adapt video-based analysis designed for C. elegans to a discrete analysis of PPN behaviour and parameterise sub-components of locomotion that together enable the worm to localise its host. We will investigate the role of key signalling molecules, i.e. neurotransmitters and receptors, in mediating these behaviours. The work will be facilitated by maturing genome sequencing projects for PPNs permitting identification of PPN orthologues of key molecular components e.g. neurotransmitter receptors, involved in PPN navigation towards its host. These will be targeted by RNAi and the impact of their reduced expression on PPN plant cue-dependent responses will thus delineate potential nematicide targets. In addition, by testing the effects of compounds, encompassing known nematicides, anthelmintics and novel neuroactive chemicals we will quantify potential efficacy against PPN host location behaviour. Subsequent heterologous expression of the PPN receptors will build on the organism-based approaches and allow a more direct comparison of chemical action on the C. elegans and PPN targets. As this derives from a comparative approach it can contribute to the design of PPN selective compounds. This effort will be facilitated by an ongoing industrial collaboration in the field of crop protection that will provide access to compound libraries representing modifications of established nematicide chemistry or compounds with unknown mode of action.

A: Beneficiaries from this research

A1: Commercial private sector Crop protection industry: There is a need for basic research that will inform development of the next generation of crop protection products with the required specificity and lack of non-target effects. This is currently hampered by a relative lack of knowledge on the physiology and pharmacology of plant parasitic nematodes. UK potato growers: The British Potato Council (BPC) estimates the UK potato production, processing and retail market has an annual value of c. £3 billion. This research will, in the long term, support potato producers who need approaches to control potato cyst nematode, particularly the cyst nematode species Globodera pallida. The pesticides used to control this nematode are the largest variable cost of the growers who use them. This represents 23% of the UK potato acreage being treated each year. The proposed project will demonstrate that fundamental research can support their agronomic needs. International growers: Nematodes are responsible for worldwide crop losses of c. $ 125 billion per annum. This research will investigate a key aspect of plant-nematode interactions in two of the most economically important genera of plant parasitic nematodes. The information gained is likely to be relevant to a wide range of growers in both intensive and subsistence agriculture. Supermarkets: Some of the major supermarkets see value in removing even the theoretical risk of pesticide residues from the potatoes they sell. The outputs of this project may in the longer term support that policy.

A2: Policy-makers DEFRA and The Scottish Government (SG) must implement the EU's amendment Directive 91/414/EEC that seeks to reduce use of hazardous crop protection chemicals in EU agriculture. The Directive involves the abrupt or gradual withdrawal of nematicides from the UK market. This is a challenge for UK potato production as it receives more crop protection treatments than other broad acre crops. DEFRA and SG need evidence of effective alternatives for potato cyst nematode control as they must also support an EU Directive specifically aimed at potato cyst nematodes (2007/33/EC) that came into force in July 2010. The research addresses basic aspects of nematode behaviour that could culminate in improved pathogen management in the longer term.

A3: General Public Most of the UK population consumes potatoes and there is a need to maintain potatoes as a nutritious and inexpensive staple food. This work will support that need in the long term.

B: Nature of benefits from this research

B1: Benefits for UK economic competitiveness The prevalence of G. pallida contributed to a decline in the UK potato crop of 11.9% between 1999 and 2003. This is a larger fall than that of other major EU producers that lack this pest. This work would build a platform to address the problem of PCN control that faces many UK producers and is one cause of their move away from this crop.

B2: Increasing the effectiveness of public services and policy It is relevant for those who seek to implement change in policies such as an amendment to Directive 91/414/EEC and implementation of 2007/33/EC to be aware that the UK science base supports its agricultural sector and is working to develop measures to address new legislation.

B3: Enhancing cultural enrichment, quality of life and health? Reducing reliance on currently used hazardous pesticides carries a benefit for UK biodiversity and sustainability of food production. A recent report from the Royal Society identified the need for training in agricultural sciences and related topics. The Postdoctoral scientist will therefore be trained in an area of considerable importance and recent neglect. Impact activities will raise awareness in the general public of some of the problems associated with food production and the role science can play in addressing these issues.