title: Role of Arabidopsis AGO6 in siRNA accumulation, DNA methylation and transcriptional gene silencing.
abstract: 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.
authors.affiliation: Department of Botany and Plant Sciences, University of California, Riverside, CA 92521, USA.
authors.forename: Xianwu
authors.initials: X
authors.lastname: Zheng
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhu
authors.forename: Avnish
authors.initials: A
authors.lastname: Kapoor
authors.forename: Jian-Kang
authors.initials: JK
authors.lastname: Zhu
mesh_terms: D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D060565:Argonaute Proteins; D001483:Base Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D016000:Cluster Analysis; D019175:DNA Methylation; D020868:Gene Silencing / Q000502:physiology*; D006570:Heterochromatin / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
chemical_list: C521197:AGO6 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D006570:Heterochromatin; D009687:Nuclear Proteins; C520629:RD29a protein, Arabidopsis; D034741:RNA, Small Interfering; C471271:ROS1 protein, Arabidopsis