Ren Yujun, Li Mengsi, Wang Wanzhen, Lan Wei, Schenke Dirk, Cai Daguang, Miao Ying
Fujian Provincial Key Laboratory of Plant Functional Biology, College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, 350002, China.
Department of Molecular Phytopathology, Christian-Albrechts University of Kiel, Kiel, Germany.
Plant J. 2022 Jan;109(1):126-143. doi: 10.1111/tpj.15559. Epub 2021 Dec 1.
MicroRNAs negatively regulate gene expression by promoting target mRNA cleavage and/or impairing its translation, thereby playing a crucial role in plant development and environmental stress responses. In Arabidopsis, the MIR840 gene is located within the overlapping 3'UTR of the PPR and WHIRLY3 (WHY3) genes, both being predicted targets of miR840* and miR840, the short maturation products of MIR840. Gain- and loss-of-function of MIR840 in Arabidopsis resulted in opposite senescence phenotypes. The highest expression levels of the MIR840 precursor transcript pre-miR840 were observed at senescence initiation, and pre-miR840 expression is significantly correlated with a reduction in PPR, but not WHY3, transcript levels. Although a reduction of transcript level of PPR, but not WHY3 transcript levels were not significantly affected by MIR840 overexpression, its protein levels were strongly reduced. Mutating the cleavage sites or replacing the target sequences abolishes the miR840*/miR840-mediated degradation of PPR transcripts and accumulation of WHY3 protein. In support for this, concurrent knockdown of both PPR and WHY3 in wild-type plants resulted in a senescence phenotype resembling that of the MIR840-overexpressing plant. This indicates that both PRR and WHY3 are targets in the MIR840-mediated senescence pathway. Moreover, single knockout mutants of PPR and WHY3 show a convergent upregulated subset of senescence-associated genes, which are also found among those induced by MIR840 overexpression. Our data provide evidence for a regulatory role of MIR840 in plant senescence.
微小RNA通过促进靶标mRNA的切割和/或损害其翻译来负向调节基因表达，从而在植物发育和环境胁迫反应中发挥关键作用。在拟南芥中，MIR840基因位于PPR和WHIRLY3（WHY3）基因重叠的3'UTR内，这两个基因均被预测为MIR840的短成熟产物miR840和miR840的靶标。拟南芥中MIR840的功能获得和丧失导致相反的衰老表型。在衰老起始时观察到MIR840前体转录本pre-miR840的最高表达水平，并且pre-miR840的表达与PPR转录水平的降低显著相关，但与WHY3转录水平无关。虽然PPR转录水平降低，但WHY3转录水平不受MIR840过表达的显著影响，但其蛋白质水平却大幅降低。突变切割位点或替换靶序列可消除miR840/miR840介导的PPR转录本降解和WHY3蛋白积累。为此提供支持的是，在野生型植物中同时敲低PPR和WHY3会导致类似于MIR840过表达植物的衰老表型。这表明PPR和WHY3都是MIR840介导的衰老途径中的靶标。此外，PPR和WHY3的单敲除突变体显示出衰老相关基因的一个趋同上调子集，这些基因也存在于MIR840过表达诱导的基因中。我们的数据为MIR840在植物衰老中的调节作用提供了证据。
