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Engineering Resistance to Wheat Stripe Rust (Puccinia striiformis f. sp. tritici) Using a Protease Recognition System

Matthew Helm: Indiana University

<div>This project focuses on a novel ‘decoy’ system for engineering resistance to wheat stripe rust (<em>Puccinia striiformis</em> f. sp. <em>tritici</em>; <em>Pst</em>) using endogenous disease resistance (R) proteins to detect <em>Pst </em>proteases. This approach represents an extension of our work on the Arabidopsis R protein RPS5, which mediates recognition of the protease AvrPphB by detecting cleavage of one of AvrPphB's targets, PBS1. We have recently shown that we can expand the recognition specificity of RPS5 by adding PBS1 ‘decoys’ that function as substrates for other pathogen proteases. Cleavage of these modified PBS1 proteins by pathogen proteases activates RPS5, thereby conferring resistance to multiple pathogens. Significantly, AvrPphB is recognized by most wheat cultivars; thus, wheat likely contains an <em>R</em> protein functionally analogous to RPS5 that recognizes cleavage of a wheat PBS1. We predict we can change the specificity of the wheat R protein simply by modifying the AvrPphB cleavage site in a wheat PBS1 ortholog. We have identified conserved <em>Pst </em>proteases that are expressed during infection and which may be translocated into host cells. Creation of wheat PBS1 decoys that are cleaved by one or more of these proteases should activate the endogenous <em>R</em> protein and thus resistance to <em>Pst</em>, one of the most economically important pathogens of wheat.</div>