Tomato-Thaumatin-like Protein Genes and Confer Resistance to Five Soil-Borne Diseases by Enhancing β-1,3-Glucanase Activity.

Although thaumatin-like proteins () are involved in resistance to a variety of fungal diseases, whether the 5 and 6 genes in tomato plants () confer resistance to the pathogenesis of soil-borne diseases has not been demonstrated. In this study, five soil-borne diseases (fungal pathogens: , , and ; bacterial pathogens: subsp. and ) were used to infect susceptible "No. 5" and disease-resistant "S-55" tomato cultivars. We found that and transcript levels were higher in susceptible cultivars treated with the three fungal pathogens than in those treated with the two bacterial pathogens and that transcript levels varied depending on the pathogen. Moreover, the and transcript levels were much higher in disease-resistant cultivars than in disease-susceptible cultivars, and the and transcript levels were higher in cultivars treated with the same fungal pathogen than in those treated with bacterial pathogens. transcript levels were higher than . and overexpression and gene-edited transgenic mutants were generated in both susceptible and resistant cultivars. Overexpression and knockout increased and decreased resistance to the five diseases, respectively. Transgenic plants overexpressing and inhibited the activities of peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) after inoculation with fungal pathogens, and the activities of POD, SOD, and APX were similar to those of fungi after infection with bacterial pathogens. The activities of CAT were increased, and the activity of β-1,3-glucanase was increased in both the fungal and bacterial treatments. Overexpressed plants were more resistant than the control plants. After and knockout plants were inoculated, POD, SOD, and APX had no significant changes, but CAT activity increased and decreased significantly after the fungal and bacterial treatments, contrary to overexpression. The activity of β-1,3-glucanase decreased in the treatment of the five pathogens, and the knocked-out plants were more susceptible to disease than the control. In summary, this study contributes to the further understanding of disease resistance mechanisms in tomato plants.