Recombinant cystatins in plants

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Protease inhibitors have long been recognized as potential biopesticides for the development of pest-resistant crops. In recent years, studies have also described indirect effects for these proteins on the plant's own physiology, potentially useful to introduce such new traits of agronomical value as pathogen, cold or drought tolerance. Taking advantage of recent developments in functional proteomics and protein engineering, this project aims at further understanding the effects of recombinant protease inhibitors in plants, and at expanding their usefulness to protect plants in drought conditions. Protease inhibitors of the plant cystatin protein family will be used as model for the project, given the number of recent reports suggesting their positive impact on plants under stress conditions. Candidate cystatins with different affinities for plant proteases will first be isolated among a collection of cystatin variants designed based on a novel protein design approach developed during the last funding cycle of this Discovery program. The selected variants will then be used for expression studies to test the feasibility of triggering variable effects in the plant depending on each variant's target proteases. Finally, the most promising variants will be used to implement drought tolerance in potato selected as a drought-susceptible crop model of major agronomic significance. A first output of this project will be a novel way to implement drought stress tolerance in crop plants, in the current climate change context where an increased incidence of drought episodes is likely to affect several major crops worldwide, including potato. Another output will be a proof-of-concept of our ability to rationally controlling the fine balance between intended and unintended effects of foreign proteins in genetically modified crops using the new tools of protein design and functional proteomics.