Race 1 strains of Pseudomonas syringae pv. tomato, which cause bacterial speck disease of tomato, are becoming increasingly common and no simply inherited genetic resistance to such strains is known. We discovered that a locus in Solanum lycopersicoides, termed Pseudomonas tomato race 1 (Ptr1), confers resistance to race 1 P. syringae pv. tomato strains by detecting the activity of type III effector AvrRpt2. In Arabidopsis, AvrRpt2 degrades the RIN4 protein, thereby activating RPS2-mediated immunity. Using site-directed mutagenesis of AvrRpt2, we found that, like RPS2, activation of Ptr1 requires AvrRpt2 proteolytic activity. Ptr1 also detected the activity of AvrRpt2 homologs from diverse bacteria, including one in Ralstonia pseudosolanacearum. The genome sequence of S. lycopersicoides revealed no RPS2 homolog in the Ptr1 region. Ptr1 could play an important role in controlling bacterial speck disease and its future cloning may shed light on an example of convergent evolution for recognition of a widespread type III effector.
Bibliographical noteFunding Information:
Funding: This work was supported by National Science Foundation (NSF) grants IOS-1546625 (to G. B. Martin) and IOS-0923312 (to J. J. Giovannoni), NSF Research Experience for Undergraduates DBI-1358843 (to M. Vachev), Laboratoire d’Excellence (LABEX), TULIP (ANR-10-LABX-41 to N. Peeters and F. Maviane-Macia), and Colciencias Depar-tamento Administrativo de Ciencia, Tecnología e Innovació grant 673 (to C. Mazo-Molina).
© 2019 The American Phytopathological Society.
- Disease resistance
- NLR-triggered immunity
- Solanum lycopersicoides
- Solanum lycopersicum
ASJC Scopus subject areas
- Agronomy and Crop Science