Role of Arabidopsis AGO6 in siRNA accumulation, DNA methylation and transcriptional gene silencing

EMBO J. 2007 Mar 21;26(6):1691-701. doi: 10.1038/sj.emboj.7601603. Epub 2007 Mar 1.


Argonautes (AGOs) are conserved proteins that contain an RNA-binding PAZ domain and an RNase H-like PIWI domain. In Arabidopsis, except for AGO1, AGO4 and AGO7, the roles of seven other AGOs in gene silencing are not known. We found that a mutation in AGO6 partially suppresses transcriptional gene silencing in the DNA demethylase mutant ros1-1. In ago6-1ros1-1 plants, RD29A promoter short interfering RNAs (siRNAs) are less abundant, and cytosine methylation at both transgenic and endogenous RD29A promoters is reduced, compared to that in ros1-1. Interestingly, the ago4-1 mutation has a stronger suppression of the transcriptional silencing phenotype of ros1-1 mutant. Analysis of cytosine methylation at the endogenous MEA-ISR, AtREP2 and SIMPLEHAT2 loci revealed that the CpNpG and asymmetric methylation levels are lower in either of the ago6-1 and ago4-1 single mutants than those in the wild type, and the levels are the lowest in the ago6-1ago4-1 double mutant. These results suggest that AGO6 is important for the accumulation of specific heterochromatin-related siRNAs, and for DNA methylation and transcriptional gene silencing, this function is partly redundant with AGO4.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Arabidopsis / genetics*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism
  • Arabidopsis Proteins / physiology*
  • Argonaute Proteins
  • Base Sequence
  • Blotting, Northern
  • Cloning, Molecular
  • Cluster Analysis
  • DNA Methylation*
  • Gene Silencing / physiology*
  • Heterochromatin / metabolism
  • Molecular Sequence Data
  • Mutation / genetics
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Phylogeny
  • RNA, Small Interfering / genetics
  • RNA, Small Interfering / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Analysis, DNA


  • AGO6 protein, Arabidopsis
  • Arabidopsis Proteins
  • Argonaute Proteins
  • Heterochromatin
  • Nuclear Proteins
  • RD29a protein, Arabidopsis
  • RNA, Small Interfering
  • ROS1 protein, Arabidopsis