MicroRNAs (miRNAs) control various biological processes by repressing target mRNAs. In plants, miRNAs mediate target gene repression via both mRNA cleavage and translational repression. However, the mechanism underlying this translational repression is poorly understood. Here, we found that Arabidopsis thaliana HYPONASTIC LEAVES1 (HYL1), a core component of the miRNA processing machinery, regulates miRNA-mediated mRNA translation but not miRNA biogenesis when it localized in the cytoplasm. Cytoplasmic HYL1 localizes to the endoplasmic reticulum and associates with ARGONAUTE1 (AGO1) and ALTERED MERISTEM PROGRAM1 (AMP1). In the cytoplasm, HYL1 monitors the distribution of AGO1 onto polysomes, binds to the mRNAs of target genes, represses their translation, and partially rescues the phenotype of the hyl1 null mutant. This study uncovered another function of HYL1 and provides insight into the mechanism of plant gene regulation.
MicroRNA319a (miR319a) controls cell division arrest in plant leaves by inhibiting the expression of TCP (TEOSINTE BRANCHED 1/CYCLOIDEA/PCF) family genes. However, it is unclear whether miR319a influences infections by necrotrophic pathogens and host susceptibility. In this study, we revealed that miR319a affected plant resistance to stem rot disease of Sclerotinia sclerotiorum. In the plants of Brassica rapa infected with S. sclerotiorum, miR319a levels increased while expression levels of several BraTCP genes significantly decreased compared with those of the uninfected plants. The overexpression of BraMIR319a in B. rapa increased the susceptibility of the plants to S. sclerotiorum and aggravated stem rot disease, whereas the overexpression of BraTCP4-1 promoted the plant resistance. Our RNA-sequencing data revealed a potential relationship between miR319a and pathogen-related WRKY genes. Chromatin immunoprecipitation (ChIP) assay, electrophoretic mobility shift assay (EMSA) and reporter transaction assay showed that BraTCP4-1 was bound to the promoters of WRKY75, WRKY70, and WRKY33 genes and directly activated these pathogen-related genes. Moreover, the expression levels of WRKY75, WRKY70, and WRKY33 in the plants overexpressing BraMIR319a declined significantly whereas those of the plants overexpressing BraTCP4-1 increased significantly. These results suggest that miR319a and its targeted gene BraTCP4 regulate stem rot resistance through pathways of WRKY genes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.