ARGONAUTE 1 homeostasis invokes the coordinate action of the microRNA and siRNA pathways

EMBO Rep. 2009 May;10(5):521-6. doi: 10.1038/embor.2009.32. Epub 2009 Apr 3.


ARGONAUTE 1 (AGO1) slices endogenous messenger RNAs (mRNAs) during both microRNA (miRNA)- and short interfering RNA (siRNA)-guided post-transcriptional silencing. We have previously reported that AGO1 homeostasis is maintained through the repressive action of miR168 on AGO1 mRNA and the stabilizing effect of AGO1 protein on miR168, but siRNA-mediated AGO1 regulation has not been reported. Here, we show that AGO1-derived siRNAs trigger RNA DEPENDENT RNA POLYMERASE 6 (RDR6)-, SUPPRESSOR OF GENE SILENCING 3 (SGS3)- and SILENCING DEFECTIVE 5 (SDE5)-dependent AGO1 silencing, which also requires DICER-LIKE 2 (DCL2) and DCL4. By varying the efficacy of miR168-guided AGO1 mRNA cleavage, we show that siRNA-mediated AGO1 silencing depends on correct miRNA targeting, pointing to coordinated regulatory actions of the miRNA and siRNA pathways during the maintenance of AGO1 homeostasis. Finally, our results reveal that dcl2, dcl3 and dcl4 mutations similarly affect post-transcriptional gene silencing (PTGS) mediated by a sense transgene and PTGS mediated by inverted repeats, validating the branched pathway model proposed previously.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Arabidopsis Proteins / physiology*
  • Argonaute Proteins
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism
  • Cell Cycle Proteins / physiology
  • MicroRNAs / metabolism*
  • Models, Biological
  • Plants, Genetically Modified / genetics
  • Plants, Genetically Modified / growth & development
  • Plants, Genetically Modified / metabolism
  • RNA, Small Interfering / metabolism*
  • Ribonuclease III / genetics
  • Ribonuclease III / metabolism
  • Ribonuclease III / physiology
  • Ribonucleases / genetics
  • Ribonucleases / metabolism
  • Ribonucleases / physiology
  • Signal Transduction / genetics
  • Signal Transduction / physiology*


  • AGO1 protein, Arabidopsis
  • Arabidopsis Proteins
  • Argonaute Proteins
  • Cell Cycle Proteins
  • MicroRNAs
  • RNA, Small Interfering
  • DCL4 protein, Arabidopsis
  • Ribonucleases
  • DCL2 protein, Arabidopsis
  • DCL3 protein, Arabidopsis
  • Ribonuclease III