A Knockout Mutation in TTM2 Confers Disease Resistance in Tomato and Pepper

The triphosphate tunnel metalloenzyme (TTM) superfamily comprises a group of enzymes that hydrolyze organophosphate substrates. They exist in all domains of life, yet the biological role of most family members is unclear. Arabidopsis thaliana encodes three TTM genes (AtTTM1, 2, 3). AtTTM2 is transcriptionally down-regulated upon infection with pseudomonas syringae and AtTTM2 knockout mutant plants exhibit enhanced pathogen resistance (Ung et al. 2014). There are 2 orthologous copies of TTM2 in tomato and pepper and we identified deleterious mutations in all copies within an EMS mutagenized population of tomato and pepper. The mutants SlTTM2a and SlTTM2b were combined by crossing to create fixed double mutants as were the mutants CaTTM2a and CaTTM2b in pepper. A number of pathology test were executed using all single mutant and double mutant combinations to determine if TTM2 knockouts would confer disease resistance in tomato and pepper. We observed a 22-35% reduction in Xanthomonas infection in tomato double mutants between 7-12 days post inoculation. We also observed a 22% reduction in powdery mildew infection in a SlTTM2a mutant 11 days post inoculation. The reduction in powdery mildew infection was also evident in plants that had been chemically primed to resist disease. These data suggest that incorporation of TTM2 mutant alleles into tomato will improve the plants defence against bacterial and fungal diseases and can be combined with chemical priming of plants for greater crop protection.