A rice-specific miRNA miR24584 enhances JA signaling by silencing OsJAZ13 to boost rice blast resistance

Abstract

Many conserved miRNAs are reported to function in plant immunity, while the discovery and functional characterization of additional immunity-related miRNAs remain an active area of research. In this study, we identified miR24584, a 24-nucleotide miRNA, as a critical positive regulator of rice immunity against Magnaporthe oryzae. The accumulation of miR24584 exhibits dynamic patterns upon pathogen challenge, with upregulation in resistant rice accessions and downregulation in susceptible accessions. The transgenic lines overexpressing miR24584 conferred resistance against diverse M. oryzae isolates, whereas suppression through target mimicry rendered plants susceptible. Furthermore, miR24584 targets the 3′ untranslated region of OsJAZ13, a transcriptional repressor of jasmonate (JA) signaling, and suppresses its expression. Transgenic overexpression of OsJAZ13 caused seedling lethality, whereas CRISPR/Cas9-mediated knockout lines displayed blast resistance accompanied by elevated JA accumulation and upregulated expression of JA-responsive marker genes. Intriguingly, following M. oryzae inoculation and chitin treatment, osjaz13 mutant lines displayed significantly increased callose deposition similarly to the transgenic lines overexpressing miR24584. Altogether, our results establish the miR24584-OsJAZ13 regulatory module that activates JA signaling to enhance physical barrier formation to optimize blast resistance. This work expands the known repertoire of immunity-associated miRNAs.