Identification of MicroRNAs Involved in Different Layers of Rice-Magnaporthe oryzae Interaction

Rice blast disease is one of the most destructive rice diseases worldwide. Rice MicroRNAs (miRNAs) play an essential role in immunity against blast fungus Magnaporthe oryzae. However, it remains unclear which miRNAs are involved in the three layers of rice-M. oryzae interaction, including pathogen associated molecular patterns (PAMPs)-triggered immunity (PTI), effector-triggered susceptibility (ETS), and effector-triggered immunity (ETI). In this study, we performed small RNA-sequencing to systemically identify miRNAs regulating PTI, ETS, and ETI in rice-M. oryzae interaction. A totally 441 miRNAs were identified, with 13, 30, and 14 miRNAs screened out and classified as regulators of PTI, ETS, and ETI, respectively. We investigated and confirmed the roles of 9 previously reported miRNAs and an uncharacterized miRNA, miR408-5p, in the three interaction processes. We demonstrated that miR1320-5p positively regulated PTI; miR396 family members and miR164a improved, whereas miR171b and miR172a suppressed ETS; miR166a enhanced, whereas miR169a and miR396 family members suppressed ETI. Moreover, we demonstrated that miR397b and miR408-5p enhanced rice susceptibility by promoting ETS and suppressing ETI; miR398b enhanced rice resistance by promoting both PTI and ETI while suppressing ETS. Our findings figured a miRNA-mediated regulatory network in which distinct miRNAs modulate PTI, ETS, and ETI against M. oryzae. This study provides new sight into the regulation mechanism of plant disease resistance.