Mechanistic Analysisand Design of Phenamacril-BasedInhibitors Targeting Myosin I of Rice Blast Disease Pathogen Magnaporthe oryzae

Magnaporthe oryzae is a devastating fungal pathogen causing blast disease in rice and other crops, threatening global grain production and food security. Phenamacril (PHA) effectively inhibits Fusarium graminearum by targeting F. graminearum myosin I (FgMyoI). However, PHA shows limited activity against M. oryzae, despite the high sequence similarity between FgMyoI and M. oryzae myosin I (MoMyoI). Using our published PHA-FgMyoI complex structure as a template, we identified K378 in MoMyoI as a key determinant of insensitivity to PHA. Substitution of K378 with methionine, the corresponding residue in FgMyoI, markedly enhanced PHA-mediated inhibition of MoMyoI ATPase activity and improved PHA efficacy against M. oryzae. Guided by structure-based design, we synthesized PHA derivatives targeting MoMyoI. Among them, NJY-10 showed improved MoMyoI binding, ATPase inhibition, and protective efficacy against rice blast disease.