Two Polyketide Synthase Genes, and , Regulated by VpLaeA Are Essential to the Virulence of .

, the causal agent of pear canker disease, typically induces cankers on the bark of infected trees and even leads to tree mortality. Secondary metabolites produced by pathogenic fungi play a crucial role in the pathogenic process. In this study, secondary metabolic regulator VpLaeA was identified in . was found to strongly affect the pathogenicity, fruiting body formation, and toxicity of secondary metabolites of . Additionally, was found to be required for the response of to some abiotic stresses. Transcriptome data analysis revealed that many of differentially expressed genes were involved in the secondary metabolite biosynthesis. Among them, about one third of secondary metabolite biosynthesis core genes were regulated by at different periods. Seven differentially expressed secondary metabolite biosynthesis core genes (, , , , , , and ) were selected for knockout. Two modular polyketide synthase genes ( and ) that were closely related to the virulence of from the above seven genes were identified. Notably, and also affected the production of fruiting body of but did not participate in the resistance of to abiotic stresses. Overall, this study demonstrates the multifaceted biological functions of in and identifies two toxicity-associated polyketide synthase genes in species fungi for the first time.