Hydrogen peroxide regulates the Osa-miR156-OsSPL2/OsTIFY11b module in rice.

Field-grown rice (Oryza sativa L.), when exposed to various environmental stresses, produces high amounts of reactive oxygen species, such as H2 O2 . MicroRNAs (miRNAs) play crucial roles in plant stress responses. This study characterized the functions of H2 O2 -regulated miRNAs in rice. Small RNA deep sequencing revealed that miR156 levels decreased following H2 O2 treatment. Searches of the rice transcriptome and degradome databases indicated that OsSPL2 and OsTIFY11b are miR156-target genes. Interactions between miR156 and OsSPL2 and OsTIFY11b were confirmed using transient expression assays through agroinfiltration. In addition, the levels of OsSPL2 and OsTIFY11b transcripts were lower in transgenic rice plants overexpressing miR156 than in wild-type plants. The OsSPL2-GFP and OsTIFY11b-GFP proteins were localized to the nucleus. Yeast two-hybrid and bimolecular fluorescence complementation assays indicated interactions between OsSPL2 and OsTIFY11b. Furthermore, OsTIFY11b interacted with OsMYC2 to regulate the expression of OsRBBI3-3, which encodes a proteinase inhibitor. The results suggested that H2 O2 accumulation in rice suppresses the expression of miR156, and induces the expression of its target genes, OsSPL2 and OsTIFY11b, whose proteins interact in the nucleus to regulate the expression of OsRBBI3-3, which is involved in plant defense.

Regulatory roles of microRNA163 in responses to stresses in Arabidopsis.

MicroRNAs (miRNAs) are small regulatory RNAs that participate in various biological processes by silencing target genes. In Arabidopsis, microRNA163 (miR163) was found to be involved in seed germination, root development, and biotic resistance. However, the regulatory roles of miR163 remain unclear. In the current study, the mir163 mutant was investigated to comprehensively understand and characterize its functions in Arabidopsis. RNA-sequencing and Gene Ontology enrichment analyses revealed that miR163 might be involved in "response to stimulus" and "metabolic process". Interestingly, "response to stress", including heat, cold, and oxidative stress, was enriched under the subcategory of "response to stimulus". We observed that miR163 and PXMT were repressed and induced under heat stress, respectively. Furthermore, the study detected significant differences in seed germination rate, hypocotyl length, and survival rate, indicating a variation in the thermotolerance between WT and mir163 mutant. The results revealed that the mir163 mutant had a lesser degree of germination inhibition by heat treatment than WT. In addition, the mir163 mutant showed a better survival rate and longer hypocotyl length under heat treatment than the WT. The metabolomes of WT and mir163 mutant were further analyzed. The contents of benzene derivatives and flavonoids were affected by miR163, which could enhance plants' defense abilities. In conclusion, miR163/targets regulated the expression of stress-responsive genes and the accumulation of defense-related metabolites to alter stress tolerance.