Tomato cysteine proteases and pathogen-derived inhibitors: the molecular arms-race towards defense and recognition

• Applicant: Professor Dr. Renier A.L. van der Hoorn
• Subject Area: Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
• Term: from 2009 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 146331277

The way how plants recognize pathogens and mount defense responses has been subject of intense research over the past decade, resulting in important working models such as the Guard Model, which explains the indirect perception mechanism by resistance gene products in gene-for-gene interactions. One of the key examples is tomato protease RCR3, which is required for recognition of pathogenic fungi producing AVR2 by the tomato resistance gene Cf-2. The Cf2 protein seems to ‘guard’ RCR3 to monitor its inhibition by AVR2 (Guard Model). However, our recent data showed that AVR2 also inhibits a more abundant protease called PIP1, suggesting that PIP1 is the operative target of AVR2 and that RCR3 acts as a decoy to trap the fungus into a recognition event (Decoy Model). In addition, we found that tomato pathogens from bacterial and oomycete kingdoms also produce inhibitors that can target RCR3 and related proteases, and that the proteases targeted by these inhibitors are under diversifying selection. These data suggest an important role for RCR3 and related proteases in defense and recognition of pathogens from different kingdoms. This proposal concerns a series of simple pathogen assays and inhibition experiments that will be used to determine: 1) the role of RCR3 and other proteases in plant-pathogen interactions (testing Guard and Decoy Models); 2) the role of variant residues in RCR3 and other proteases in inhibition and recognition of AVR2 and inhibitors from other kingdoms; 3) test novel ways of crop protection using inhibitor-insensitive proteases and improved sensors for pathogen-derived inhibitors. Thus, with a series of straightforward, feasible assays and through a continuation of a fruitful collaboration with Dr. Sophien Kamoun (Sainsbury lab, Norwich, UK), this project aims to deliver answers to many of the current key questions in molecular plant pathology.

• DFG Programme: Research Grants
• International Connection: United Kingdom
• Participating Person: Professor Sophien Kamoun, Ph.D.