Mr-lac3 and Mr-lcc2 in Regulate Conidiation and Maturation, Enhancing Tolerance to Abiotic Stresses and Pathogenicity.

As a type of multicopper oxidase, laccases play multiple biological roles in entomopathogenic fungi, enhancing their survival, development, and pathogenicity. However, the mechanisms by which laccases operate in these fungi remain under-researched. In this study, we identified two laccase-encoding genes, and , from , both of which are highly expressed during conidiation. Knocking out and resulted in a significant increase in the conidial yields of . Furthermore, the relative expression levels of upstream regulators associated with the conidiation pathway were markedly up-regulated in and compared to the wild-type strain during conidiation, indicating that and negatively regulate conidia formation. qRT-PCR analyses revealed that and are regulated by the pigment synthesis gene cluster, including , , and , and they also provide feedback regulation to jointly control pigment synthesis. Additionally, and significantly reduced the trehalose content in conidia and increased the sensitivity to cell wall-perturbing agents, such as Congo red and guaiacol, which led to a marked decrease in tolerance to abiotic stresses. In conclusion, the laccases Mr-lac3 and Mr-lcc2 negatively regulate conidia formation while positively regulating conidial maturation, thereby enhancing tolerance to abiotic stresses and pathogenicity.