Antisilencing role of the RNA-directed DNA methylation pathway and a histone acetyltransferase in Arabidopsis.
REPRESSOR OF SILENCING 1 (ROS1) is a DNA demethylation enzyme that was previously identified during a genetic screen for the silencing of both RD29A-LUC and 35S-NPTII transgenes on a T-DNA construct. Here we performed a genetic screen to identify additional mutants in which the 35S-NPTII transgene is silenced. We identified several alleles of ros1 and of the following components of the RNA-directed DNA methylation (RdDM) pathway: NRPD1 (the largest subunit of polymerase IV), RDR2, NRPE1 (the largest subunit of polymerase V), NRPD2, AGO4, and DMS3. Our results show that the silencing of 35S-NPTII in the RdDM pathway mutants is due to the reduced expression of ROS1 in the mutants. We also identified a putative histone acetyltransferase (ROS4) from the genetic screen. The acetyltransferase contains a PHD-finger domain that binds to unmethylated histone H3K4. The mutation in ROS4 led to reduction of H3K18 and H3K23 acetylation levels. We show that the silencing of 35S-NPTII and some transposable element genes was released by the ddm1 mutation but that this also required ROS4. Our study identifies a unique antisilencing factor, and reveals that the RdDM pathway has an antisilencing function due to its role in maintaining ROS1 expression.
State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences,  China Agricultural University, Beijing 100193,  China.
Xiaojie
X
Li
Weiqiang
W
Qian
Yusheng
Y
Zhao
Chunlei
C
Wang
Jie
J
Shen
Jian-Kang
JK
Zhu
Zhizhong
Z
Gong
D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D005816:Genetic Complementation Test; D049452:Green Fluorescent Proteins / Q000378:metabolism; D051548:Histone Acetyltransferases / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D007612:Kanamycin / Q000494:pharmacology; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism*; D019076:Transgenes
D029681:Arabidopsis Proteins; D006657:Histones; D009687:Nuclear Proteins; C471271:ROS1 protein, Arabidopsis; D049452:Green Fluorescent Proteins; D007612:Kanamycin; D012313:RNA; D051548:Histone Acetyltransferases