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MicroRNA168 (miR168) is a key miRNA that targets Argonaute1 (AGO1), a major component of the RNA-induced silencing complex1,2. Previously, we reported that miR168 expression was responsive to infection by Magnaporthe oryzae, the causal agent of rice blast disease3. However, how miR168 regulates immunity to rice blast and whether it affects rice development remains unclear. Here, we report our discovery that the suppression of miR168 by a target mimic (MIM168) not only improves grain yield and shortens flowering time in rice but also enhances immunity to M. oryzae. These results were validated through repeated tests in rice fields in the absence and presence of rice blast pressure. We found that the miR168–AGO1 module regulates miR535 to improve yield by increasing panicle number, miR164 to reduce flowering time, and miR1320 and miR164 to enhance immunity. Our discovery demonstrates that changes in a single miRNA enhance the expression of multiple agronomically important traits. In rice, it is known that miR168 regulates AGO1. Using a target mimic approach to suppress the microRNA enhances resistance against rice blast disease, increases grain yield and shortens growth period, including in field trials.

MicroRNAs (miRNAs) are known to fine-tune growth, development, and stress-induced responses. Osa-miR1873 is a rice-specific miRNA targeting LOC_Os05g01790. Here, we show that Osa-miR1873 fine-tunes rice immunity against Magnaporthe oryzae and yield traits via LOC_Os05g01790. Osa-miR1873 was significantly upregulated in a susceptible accession but downregulated in a resistance accession at 24 h post-inoculation (hpi) of M. oryzae. Overexpressing Osa-miR1873 enhanced susceptibility to M. oryzae and compromised induction of defense responses. In contrast, blocking Osa-miR1873 through target mimicry compromised susceptibility to M. oryzae and enhanced induction of defense responses. Altered expression of Osa-miR1873 also resulted in some defects in yield traits, including grain numbers and seed setting rate. Moreover, overexpression of the target gene LOC_Os05g01790 increased rice blast disease resistance but severely penalized growth and yield. Taken together, we demonstrate that Osa-miR1873 fine-tunes the rice immunity-growth trade-off via LOC_Os05g01790, and blocking Osa-miR1873 could improve blast disease resistance without significant yield penalty. Thus, the Osa-miR1873-LOC_Os05g01790 regulatory module is valuable in balancing yield traits and blast resistance.

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.

MicroRNAs (miRNAs) play essential roles in rice immunity against Magnaporthe oryzae, the causative agent of rice blast disease. Osa-miR162a targets Dicer-like 1 (DCL1) genes, which play vital roles in miRNA biogenesis and act as negative regulators in rice immunity. Here we demonstrate that Osa-miR162a improves rice immunity against M. oryzae and balances the trade-off between rice yield and resistance. Overexpression of Osa-miR162a compromises rice susceptibility to M. oryzae accompanying enhanced induction of defense-related genes and accumulation of hydrogen peroxide (H2O2). In contrast, blocking miR162 by overexpressing a target mimic of miR162 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 reduced yield per plant, whereas blocking miR162 leads to an increased number of grains per panicle, resulting in increased yield per plant. Altered accumulation of miR162 had limited impact on the expression of OsDCL1. Together, our results indicate that Osa-miR162a improves rice blast resistance and plays a role in the balance of trade-off between resistance and yield.

Additional file 1: Figure S1. Overexpression of Osa-miR162a leads to enhanced resistance to Magnaporthe oryzae upon spray-inoculation. (a) Disease phenotypes on leaves of the indicated lines following spray-inoculation with M. oryzae strain GZ8. The phenotype was captured at 5 days post-inoculation. Bar = 5 mm. (b) Quantification analysis of the fungal biomass in (a). Relative fungal biomass was measured by using the ratio of DNA level of M. oryzae Pot2 gene against the rice genomic ubiquitin DNA level. Error bars indicate SD (n = 3). Different letters above the bars indicate a significant difference (P

Additional file 2: Figure S2. Overexpression of Osa-miR162a results in enhanced resistance to multiple Magnaporthe oryzae strains. (a) Disease phenotypes on leaves of NPB, OX162 and MIM162 following punch-inoculation with field-derived M. oryzae strains. The phenotype was captured at 5 days post-inoculation. Bars = 5 mm. (b-e) Quantification analysis of the fungal biomass in (a). Relative fungal biomass was measured by using the ratio of DNA level of M. oryzae Pot2 gene against the rice genomic ubiquitin DNA level. Error bars indicate SD (n = 3). Different letters above the bars indicate a significant difference (P

Additional file 4: Table S1. Primers used in this study.

Additional file 3: Figure S3. Osa-miR162a does not repress the expression of DUF292. (a) The alignment of Osa-miR162a and Osa-miR162b with MIM162. (b) The sequence alignment of Osa-miR162a with target sites of candidate genes. Mismatched nucleotides were highlighted in red colors. (c and d) Quantitative reverse transcription polymerase chain reaction (RT-qPCR) data indicate amounts of Osa-miR162a levels in OX162 (c) and MIM162 lines (d) in comparison with Nipponbare (NPB). For qPCR, Data are shown as mean ± SD (n = 3). Different letters indicate a significant difference at 5% level via Tukey-Kramer test. All the experiments were repeated two times with similar results.

Circular RNAs (circRNAs) play roles in various biological processes, but their functions in the rice (Oryza sativa) response to Magnaporthe oryzae remain elusive. Here, we demonstrate that circRNAs are involved in the rice-M. oryzae interaction using comparative circRNA-sequencing and transgenic approaches. We identified 2932 high-confidence circRNAs from young leaves of the blast-resistant accession International Rice Blast Line Pyricularia-Kanto51-m-Tsuyuake (IR25) and the blast-susceptible accession Lijiangxin Tuan Heigu (LTH) under M. oryzae-infected or uninfected conditions; 636 were detected specifically upon M. oryzae infection. The circRNAs in IR25 were significantly more diverse than those in LTH, especially under M. oryzae infection. Particularly, the number of circRNAs generated per parent gene was much higher in IR25 than in LTH and increased in IR25 but decreased in LTH upon M. oryzae infection. The higher diversity of circRNAs in IR25 was further associated with more frequent 3′ and 5′ alternative back-splicing and usage of complex splice sites. Moreover, a subset of circRNAs was differentially responsive to M. oryzae in IR25 and LTH. We further confirmed that circR5g05160 promotes rice immunity against M. oryzae. Therefore, our data indicate that circRNA diversity is associated with different responses to M. oryzae infection in rice and provide a starting point to investigate a new layer of regulation in the rice-M. oryzae interaction.