P-140 - N-glycosylation Enables Smut Fungal Nge1 Orthologs to Counteract PMEI Evasion from Recognition

Cell wall integrity (CWI) is co-regulated by cell wall modifying enzymes, Pectin methylesterase (PME) and its inhibitor (PMEI). PME de-methylesterifies pectins, making them susceptible to degradation and loosening the CW, thereby facilitating pathogen invasion. Conversely, inhibitory effects from PMEI strengthen the wall. However, how fungal pathogens override PMEIs remains unclear. Here, we demonstrate that the smut fungus Ustilago maydis N-glycosylated Effector 1 (Nge1) targets maize multiple PMEIs including PMEI45, PMEI46, and auto-inhibitory PRO-domains in PMEs to manipulate CWI and confer virulence advantages. Interactions between Nge1 and these PMEIs liberate their targets, PME19 and PME20. Consequently, the free PMEs could loosen the cell walls, enhancing U. maydis virulence. Notably, Nge1 interaction with PMEI45, but not PMEI46, requires glycosylation, as demonstrated by functional complementation with N-glycosylated Nge1 orthologs. Our findings reveal that glycan modifications drive the co-evolution of effectors and their targets, enabling effectors to overcome host defensive PMEIs that have evolved to evade them.