An OsPRMT5-OsAGO2/miR1875-OsHXK1 module regulates rice immunity to blast disease

Rice ARGONAUTE2(OsAGO2)is a core component of the rice RNA-induced silencing complex(RISC),which is repressed by Magnaporthe oryzae(M.oryzae)infection.Whether and how OsAGO2-mediated gene silencing plays a role in rice blast resistance and which sRNAs participate in this process are unknown.Our results indicate that OsAGO2 is a key immune player that manipulates rice defense responses against blast disease.OsAGO2 associates with the 24-nt miR1875 and binds to the promoter region of HEXOKINASE1(OsHXK1),which causes DNA methylation and leads to gene silencing.Our multiple genetic evidence showed that,without M.oryzae infection,OsAGO2/miR1875 RISC promoted OsHXK1 promoter DNA methylation and OsHXK1 silencing;after M.oryzae infection,the reduced OsAGO2/miR1875 led to a relatively activated OsHXK1 expression.OsHXK1 acts as a positive regulator of blast disease resistance that OsHXK1-OE rice exhibited enhanced resistance,whereas Cas9-Oshxk1 rice showed reduced resistance against M.oryzae infection.OsHXK1 may function through its sugar sensor activity as glucose induced defense-related gene expression and reactive oxygen species(ROS)accumulation in Nipponbare and OsHXK1-OE but not in Cas9-Oshxk1 rice.OsAGO2 itself is delicately regulated by OsPRMT5,which senses M.oryzae infection and attenuates OsAGO2-mediated gene silencing through OsAGO2 arginine methylation.Our study reveals an OsPRMT5-OsAGO2/miR1875-OsHXK1 regulatory module that fine tunes the rice defense response to blast disease.