ARGONAUTE10 promotes the degradation of miR165/6 through the SDN1 and SDN2 exonucleases in Arabidopsis

PLoS Biol. 2017 Feb 23;15(2):e2001272. doi: 10.1371/journal.pbio.2001272. eCollection 2017 Feb.


The degradation of small RNAs in plants and animals is associated with small RNA 3' truncation and 3' uridylation and thus relies on exonucleases and nucleotidyl transferases. ARGONAUTE (AGO) proteins associate with small RNAs in vivo and are essential for not only the activities but also the stability of small RNAs. AGO1 is the microRNA (miRNA) effector in Arabidopsis, and its closest homolog, AGO10, maintains stem cell homeostasis in meristems by sequestration of miR165/6, a conserved miRNA acting through AGO1. Here, we show that SMALL RNA DEGRADING NUCLEASES (SDNs) initiate miRNA degradation by acting on AGO1-bound miRNAs to cause their 3' truncation, and the truncated species are uridylated and degraded. We report that AGO10 reduces miR165/6 accumulation by enhancing its degradation by SDN1 and SDN2 in vivo. In vitro, AGO10-bound miR165/6 is more susceptible to SDN1-mediated 3' truncation than AGO1-bound miR165/6. Thus, AGO10 promotes the degradation of miR165/6, which is contrary to the stabilizing effect of AGO1. Our work identifies a class of exonucleases responsible for miRNA 3' truncation in vivo and uncovers a mechanism of specificity determination in miRNA turnover. This work, together with previous studies on AGO10, suggests that spatially regulated miRNA degradation underlies stem cell maintenance in plants.

MeSH terms

  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / metabolism*
  • Argonaute Proteins / metabolism*
  • Exoribonucleases / metabolism*
  • Gene Expression Regulation, Plant
  • Methylation
  • MicroRNAs / genetics
  • MicroRNAs / metabolism*
  • Mutation / genetics
  • Plants, Genetically Modified
  • Protein Binding
  • RNA Stability*
  • RNA-Induced Silencing Complex / metabolism


  • AGO1 protein, Arabidopsis
  • AGO10 protein, Arabidopsis
  • Arabidopsis Proteins
  • Argonaute Proteins
  • MIRN165 microRNA, Arabidopsis
  • MIRN166 microRNA, Arabidopsis
  • MicroRNAs
  • RNA-Induced Silencing Complex
  • Exoribonucleases
  • SDN1 protein, Arabidopsis
  • SDN2 protein, Arabidopsis