CRISPR/Cas9-Mediated SlMYBS2 Mutagenesis Reduces Tomato Resistance to Phytophthora infestans

Phytophthora infestans (P. infestans) recently caused epidemics of tomato late blight. Our study aimed to identify the function of the SlMYBS2 gene in response to tomato late blight. To further investigate the function of SlMYBS2 in tomato resistance to P. infestans, we studied the effects of SlMYBS2 gene knock out. The SlMYBS2 gene was knocked out by CRISPR-Cas9, and the resulting plants (SlMYBS2 gene knockout, slmybs2-c) showed reduced resistance to P. infestans, accompanied by increases in the number of necrotic cells, lesion sizes, and disease index. Furthermore, after P. infestans infection, the expression levels of pathogenesis-related (PR) genes in slmybs2-c plants were significantly lower than those in wild-type (AC) plants, while the number of necrotic cells and the accumulation of reactive oxygen species (ROS) were higher than those in wild-type plants. Taken together, these results indicate that SlMYBS2 acts as a positive regulator of tomato resistance to P. infestans infection by regulating the ROS level and the expression level of PR genes.