Study : Positive roles for Osa-miR7695 in regulating defense responses against the rice blast fungus


Positive roles for Osa-miR7695 in regulating defense responses against the rice blast fungus
MicroRNAs (miRNAs) are small non-coding RNAs that function as post-transcriptional regulators of gene expression in eukaryotes. In rice, miR7695 targets an alternatively spliced transcript of natural resistance-associated macrophage protein 6 (OsNramp6) encoding an iron transporter whose expression is regulated by infection with the rice blast fungus Magnaporthe oryzae. Rice plants grown under high iron supply showed blast resistance, which supports that iron is a factor in controlling blast resistance by still unknown mechanisms. Here, iron accumulated near M. oryzae appressoria, the sites of pathogen entry, and in cells surrounding infected regions of the rice leaf. Activation-tagged MIR7695 rice plants (MIR7695-Ac) exhibited enhanced resistance to M. oryzae infection. RNA-seq analysis revealed that blast resistance in MIR7695-Ac plants was associated with strong induction of defense-related genes, including pathogenesis-related and diterpenoid biosynthetic genes. Levels of phytoalexins during pathogen infection were higher in MIR7695-Ac than wild-type plants. Early phytoalexin biosynthetic genes, OsCPS2 and OsCSP4, were highly upregulated in rice plants grown under high iron supply. Our data indicate that miR7695 positively regulates rice immunity while establishing links between defense and iron signaling in rice. MiR7695-mediated regulation of OsNramp6 has great potential for the development of strategies to control rice blast disease. Overall design: 8 samples in total: 2 genotypes (WT-Az, MIR7695-Ac) with 2 treatments (Control, Infected), 2 biological replicates each. Samples are: WT-Az (Control); MIR7695-Ac (Control); WT-Az (Infected); MIR7695-Ac (Infected)


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