Protease inhibitors and directed evolution: enhancing plant resistance to nematodes

Plant nematodes are agricultural pests, the control of which relies on chemical nematicides and fumigants that are among the most toxic and environmentally damaging of all agrochemicals. New approaches to control, based on transgenic resistance, would provide important health and environmental benefits. In this chapter we consider briefly some targets for engineering nematode resistance and discuss the use of plant protease inhibitors as anti-feedants. This approach has provided plants that display good levels of resistance against a range of nematode species. To enhance this defence strategy further we are investigating the value of directed evolution to improve the characteristics of protease inhibitors. We describe the approaches of DNA shuffling and phage display that are being used to create and screen variant libraries in the search for inhibitors with improved features.