Regulatory link between DNA methylation and active demethylation in Arabidopsis.
De novo DNA methylation through the RNA-directed DNA methylation (RdDM) pathway and active DNA demethylation play important roles in controlling genome-wide DNA methylation patterns in plants. Little is known about how cells manage the balance between DNA methylation and active demethylation activities. Here, we report the identification of a unique RdDM target sequence, where DNA methylation is required for maintaining proper active DNA demethylation of the Arabidopsis genome. In a genetic screen for cellular antisilencing factors, we isolated several REPRESSOR OF SILENCING 1 (ros1) mutant alleles, as well as many RdDM mutants, which showed drastically reduced ROS1 gene expression and, consequently, transcriptional silencing of two reporter genes. A helitron transposon element (TE) in the ROS1 gene promoter negatively controls ROS1 expression, whereas DNA methylation of an RdDM target sequence between ROS1 5' UTR and the promoter TE region antagonizes this helitron TE in regulating ROS1 expression. This RdDM target sequence is also targeted by ROS1, and defective DNA demethylation in loss-of-function ros1 mutant alleles causes DNA hypermethylation of this sequence and concomitantly causes increased ROS1 expression. Our results suggest that this sequence in the ROS1 promoter region serves as a DNA methylation monitoring sequence (MEMS) that senses DNA methylation and active DNA demethylation activities. Therefore, the ROS1 promoter functions like a thermostat (i.e., methylstat) to sense DNA methylation levels and regulates DNA methylation by controlling ROS1 expression.
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47906; and.
Mingguang
M
Lei
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47906; and Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Science, Chinese Academy of Sciences, Shanghai 200032, China.
Huiming
H
Zhang
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47906; and.
Russell
R
Julian
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47906; and.
Kai
K
Tang
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47906; and Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Science, Chinese Academy of Sciences, Shanghai 200032, China.
Shaojun
S
Xie
Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47906; and Shanghai Center for Plant Stress Biology, Shanghai Institutes for Biological Science, Chinese Academy of Sciences, Shanghai 200032, China jkzhu@purdue.edu.
Jian-Kang
JK
Zhu
D017360:Arabidopsis / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics; D001483:Base Sequence; D003433:Crosses, Genetic; D019175:DNA Methylation / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D026901:Membrane Transport Proteins / Q000235:genetics; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D018749:RNA, Plant / Q000378:metabolism; D019076:Transgenes
D029681:Arabidopsis Proteins; D026901:Membrane Transport Proteins; D009687:Nuclear Proteins; D010940:Plant Proteins; D018749:RNA, Plant; C471271:ROS1 protein, Arabidopsis; C078729:sucrose transport protein, plant; D017853:Phosphotransferases (Alcohol Group Acceptor); C063242:hygromycin-B kinase
DNA demethylase; ROS1; methylstat; rheostat; sensor