Physiological and transcriptomic analysis of tomato leaf mold resistance gene Cf-12 against Cladosporium fulvum

Tomato leaf mold caused by Cladosporium fulvum (C. fulvum, syn. Passalora fulva) is one of the most devastating diseases affecting tomatoes. C. fulvum evolves very fast. Cultivars containing Cf that are resistant to C. fulvum are easily infected by newly differentiated physiological races. In this study, physiological and biochemical indicators of Cf-12 plants and knockout lines Slcf-12-28 were determined, and transcriptomic analysis was performed after inoculation to elucidate the molecular mechanism of the incompatibility interaction between Cf-12 and C. fulvum. The results showed that Cf-12 could quickly recognize the effectors secreted by C. fulvum and induce a large number of reactive oxygen species at the infection site, which led to a rapid increase in antioxidant enzyme activities and the accumulation of antibacterial substances such as phenylalanine ammonia-lyase, phytoalexin, lignin, phenols, and flavonoids during secondary metabolism. At the same time, it induces the upregulation of AOS, AOC and OPR in the JA synthesis pathway, and activates the expression of early resistance response genes initiated by JA. Finally, local hypersensitive necrosis occurred in the cells around the infection points of C. fulvum, limiting further infection of C.fulvum. In conclusion, these results contribute to further understanding of the molecular mechanism of the incompatibility interaction between Cf and C. fulvum.