TY - JOUR
T1 - Role of Arabidopsis ARGONAUTE4 in RNA-directed DNA methylation triggered by inverted repeats
AU - Zilberman, Daniel
AU - Cao, Xiaofeng
AU - Johansen, Lisa K.
AU - Xie, Zhixin
AU - Carrington, James C.
AU - Jacobsen, Steven E.
N1 - Funding Information:
We thank Marjori Matzke for HxK seeds; Elliot Meyerowitz for AP1RNAi seeds; H. Norem, F. Rastegar, J. Takimoto, A. Sreepathy, and S. Duong for technical assistance; and Simon Chan, Carey Fei Li, Anders Lindroth, and Lianna Johnson for helpful discussions and critical review of the manuscript. This work was supported by grants from the National Institute of Health (GM07185 to D.Z., GM60398 to S.E.J., and AI43288 and F32A1051097 to J.C.C.), and National Science Foundation (MCB-0209836) to J.C.C.
PY - 2004/7/13
Y1 - 2004/7/13
N2 - In a number of organisms, transgenes containing transcribed inverted repeats (IRs) that produce hairpin RNA can trigger RNA-mediated silencing, which is associated with 21-24 nucleotide small interfering RNAs (siRNAs) [1]. In plants, IR-driven RNA silencing also causes extensive cytosine methylation of homologous DNA in both the transgene "trigger" and any other homologous DNA sequences - "targets" [2]. Endogenous genomic sequences, including transposable elements and repeated elements, are also subject to RNA-mediated silencing. The RNA silencing gene ARGONAUTE4 (AGO4) is required for maintenance of DNA methylation at several endogenous loci and for the establishment of methylation at the FWA gene [3, 4]. Here, we show that mutation of AGO4 substantially reduces the maintenance of DNA methylation triggered by IR transgenes, but AGO4 loss-of-function does not block the initiation of DNA methylation by IRs. AGO4 primarily affects non-CG methylation of the target sequences, while the IR trigger sequences lose methylation in all sequence contexts. Finally, we find that AGO4 and the DRM methyltransferase genes are required for maintenance of siRNAs at a subset of endogenous sequences, but AGO4 is not required for the accumulation of IR-induced siRNAs or a number of endogenous siRNAs, suggesting that AGO4 may function downstream of siRNA production.
AB - In a number of organisms, transgenes containing transcribed inverted repeats (IRs) that produce hairpin RNA can trigger RNA-mediated silencing, which is associated with 21-24 nucleotide small interfering RNAs (siRNAs) [1]. In plants, IR-driven RNA silencing also causes extensive cytosine methylation of homologous DNA in both the transgene "trigger" and any other homologous DNA sequences - "targets" [2]. Endogenous genomic sequences, including transposable elements and repeated elements, are also subject to RNA-mediated silencing. The RNA silencing gene ARGONAUTE4 (AGO4) is required for maintenance of DNA methylation at several endogenous loci and for the establishment of methylation at the FWA gene [3, 4]. Here, we show that mutation of AGO4 substantially reduces the maintenance of DNA methylation triggered by IR transgenes, but AGO4 loss-of-function does not block the initiation of DNA methylation by IRs. AGO4 primarily affects non-CG methylation of the target sequences, while the IR trigger sequences lose methylation in all sequence contexts. Finally, we find that AGO4 and the DRM methyltransferase genes are required for maintenance of siRNAs at a subset of endogenous sequences, but AGO4 is not required for the accumulation of IR-induced siRNAs or a number of endogenous siRNAs, suggesting that AGO4 may function downstream of siRNA production.
UR - http://www.scopus.com/inward/record.url?scp=3142640878&partnerID=8YFLogxK
U2 - 10.1016/j.cub.2004.06.055
DO - 10.1016/j.cub.2004.06.055
M3 - Article
C2 - 15242620
AN - SCOPUS:3142640878
SN - 0960-9822
VL - 14
SP - 1214
EP - 1220
JO - Current Biology
JF - Current Biology
IS - 13
ER -