Fusarium sacchari Effector FsMEP1 Contributes to Virulence by Disturbing Localization of Thiamine Thiazole Synthase ScTHI2 from Sugarcane

<i>Fusarium sacchari</i> is a significant pathogenic fungus that causes sugarcane Pokkah Boeng. Proteins secreted by pathogenic fungi can be delivered into hosts to suppress plant immunity and establish infection. However, there is still much to be discovered regarding <i>F. sacchari</i>'s secreted effectors in overcoming plant immunity. In this paper, we characterize a novel effector called FsMEP1, which is essential for the virulence of <i>F. sacchari</i>. FsMEP1 contains a conserved zinc-binding motif sequence, HEXXH, and is highly expressed during host infection. Using the <i>Agrobacterium tumefaciens</i>-mediated transient expression system, it was confirmed that FsMEP1 could suppress Bcl-2-associated X protein (BAX)-triggered cell death, callose deposition, and ROS explosion in <i>Nicotiana benthamiana</i>. Furthermore, the deletion of FsMEP1 demonstrated its requirement for contributing to the pathogenicity of <i>F. sacchari</i> in sugarcane. Further analysis revealed that FsMEP1 could interact with the sugarcane thiamine thiazole synthase ScTHI2 and disrupt its normal localization, thereby inhibiting the synthesis of thiamine and the defense responses mediated by ScTHI2. Based on these findings, we propose that ScTHI2 represents a potential molecular target for improving sugarcane resistance to Pokkah Boeng disease.