Abstract
MicroRNAs (miRNAs) play essential roles in rice immunity against Magnaporthe oryzae, the causative agent of rice blast disease. Here we demonstrate that Osa-miR162a fine-tunes rice immunity against M. oryzae and yield traits. Overexpression of Osa-miR162a enhances rice resistance to M. oryzae accompanying enhanced induction of defense-related genes and accumulation of hydrogen peroxide (H2O2). In contrast, blocking Osa-miR162 by overexpressing a target mimic of Osa-miR162a enhances susceptibility to blast fungus associating with compromised induction of defense-related gene expression and H2O2 accumulation. Moreover, the transgenic lines overexpressing Osa-miR162a display decreased seed setting rate resulting in slight reduced yield per plant, whereas the transgenic lines blocking Osa-miR162 show an increased number of grains per panicle, resulting in increased yield per plant. Altered accumulation of Osa-miR162 had a limited impact on the expression of rice Dicer-like 1 (OsDCL1) in these transgenic lines showing normal gross morphology, and silencing of OsDCL1 led to enhanced resistance to blast fungus similar to that caused by overexpression of Osa-miR162a, suggesting the involvement of OsDCL1 in Osa-miR162a-regulated resistance. Together, our results indicate that Osa-miR162a is involved in rice immunity against M. oryzae and fine-tunes resistance and yield.
Highlights
Plants mount a multi-layered immune system in fighting against the invasion of pathogens, and small RNAs are essential regulators in this process (Katiyar-Agarwal and Jin 2010; Weiberg et al 2014). miRNAs are a subset of non-coding small RNAs of 20–24 nucleotides and play vital roles in the regulation of gene expression either by chromatin methyl modification, mRNA cleavage, or translational inhibition (Yu et al 2017)
Osa-miR162a Is Differentially Responsive to M. oryzae in Susceptible and Resistant Accessions To explore the involvement of Osa-miR162a in rice blast resistance, we examined the amounts of Osa-miR162a in a highly susceptible accession Lijiang xin Tuan Heigu (LTH) and a resistant accession IRBLKm-Ts
IRBLKm-Ts showed reduced accumulation at 12 and 48 hpi but increased at 24 hpi (Fig. 1b), indicating Osa-miR162a was involved in riceM. oryzae interaction
Summary
Plants mount a multi-layered immune system in fighting against the invasion of pathogens, and small RNAs are essential regulators in this process (Katiyar-Agarwal and Jin 2010; Weiberg et al 2014). miRNAs are a subset of non-coding small RNAs of 20–24 nucleotides (nt) and play vital roles in the regulation of gene expression either by chromatin methyl modification, mRNA cleavage, or translational inhibition (Yu et al 2017). Plants mount a multi-layered immune system in fighting against the invasion of pathogens, and small RNAs are essential regulators in this process (Katiyar-Agarwal and Jin 2010; Weiberg et al 2014). MiRNAs are a subset of non-coding small RNAs of 20–24 nucleotides (nt) and play vital roles in the regulation of gene expression either by chromatin methyl modification, mRNA cleavage, or translational inhibition (Yu et al 2017). DCL1 plays miR162 is involved in multiple abiotic stress responses in plants. In switchgrass (Panicum virgatum), the accumulation of miR162 was significantly changed under drought stress (Sun et al 2012). Li et al Rice (2020) 13:38 virus suppressors, such as Tombusvirus p19 and Cucumovirus 2b, had a binding preference for miR162 to counteract host antiviral RNA silencing, a plant immune response during viral infection initiation (Pertermann et al 2018)
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