MoMad2 With a Conserved Function in the Spindle Assembly Checkpoint Is Required for Maintaining Appressorial Turgor Pressure and Pathogenicity of Rice Blast Fungus.

Abstract

Mad2, a conserved core component of the spindle assembly checkpoint (SAC) in eukaryotes, delays anaphase onset in case of incorrect kinetochore-microtubule attachment. However, its functions in plant-pathogenic fungi remain largely unknown. Here, we identified the Mad2 homologue in rice blast fungus Magnaporthe oryzae (MoMad2), which shows high similarity with Mad2 in fission yeast. When expressed in fission yeast, MoMad2 associated with native SpMad1 and SpCdc20, and successfully rescued the ΔSpmad2 mutant's defect in arresting anaphase onset upon damaged spindle, indicating the conserved SAC function of MoMad2. Moreover, MoMad2 interacted with MoMad1 and depends on MoMad1 for its nuclear envelope-localisation. Although it plays a dispensable role in M. oryzae growth, MoMad2 is required for tolerance to the microtubule depolymerising agent treatment. ΔMomad2 mutants exhibited shorter hyphal compartments and earlier conidial germination and appressorium formation, suggesting that MoMad2 deletion shortens M. oryzae's mitotic cell cycle due to defective SAC arrest. Additionally, knockout of MoMAD2 decreased the appressorial turgor pressure, impaired appressorium penetration and compromised M. oryzae pathogenicity. Taken together, our findings revealed that MoMad2, as a conserved component in SAC signalling, is essential for full pathogenicity of rice blast fungus.