Effector Sntf2 Interacted with Chloroplast-Related Protein Mdycf39 Promoting the Colonization of in Apple Leaf.

Glomerella leaf spot of apple, caused by , is a devastating disease that leads to severe defoliation and fruit spots. The species secretes a series of effectors to manipulate the host's immune response, facilitating its colonization in plants. However, the mechanism by which the effector of inhibits the defenses of the host remains unclear. In this study, we reported a novel effector Sntf2 of . The transient expression of inhibits BAX-induced cell death in tobacco plants. Sntf2 suppresses plant defense responses by reducing callose deposition and HO accumulation. is upregulated during infection, and its deletion reduces virulence to the plant. Sntf2 is localized to the chloroplasts and interacts with Mdycf39 (a chloroplast PSII assembly factor) in apple leaves. The overexpression line increases susceptibility to , whereas the transgenic silent line does not grow normally with pale white leaves, indicating that Sntf2 disturbs plant defense responses and growth by targeting Mdycf39.