title: Mutation of a major CG methylase in rice causes genome-wide hypomethylation, dysregulated genome expression, and seedling lethality.
abstract: Cytosine methylation at CG sites ((m)CG) plays critical roles in development, epigenetic inheritance, and genome stability in mammals and plants. In the dicot model plant Arabidopsis thaliana, methyltransferase 1 (MET1), a principal CG methylase, functions to maintain (m)CG during DNA replication, with its null mutation resulting in global hypomethylation and pleiotropic developmental defects. Null mutation of a critical CG methylase has not been characterized at a whole-genome level in other higher eukaryotes, leaving the generality of the Arabidopsis findings largely speculative. Rice is a model plant of monocots, to which many of our important crops belong. Here we have characterized a null mutant of OsMet1-2, the major CG methylase in rice. We found that seeds homozygous for OsMet1-2 gene mutation (OsMET1-2(-/-)), which directly segregated from normal heterozygote plants (OsMET1-2(+/-)), were seriously maldeveloped, and all germinated seedlings underwent swift necrotic death. Compared with wild type, genome-wide loss of (m)CG occurred in the mutant methylome, which was accompanied by a plethora of quantitative molecular phenotypes including dysregulated expression of diverse protein-coding genes, activation and repression of transposable elements, and altered small RNA profiles. Our results have revealed conservation but also distinct functional differences in CG methylases between rice and Arabidopsis.
authors.affiliation: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
authors.forename: Lanjuan
authors.initials: L
authors.lastname: Hu
authors.affiliation: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
authors.forename: Ning
authors.initials: N
authors.lastname: Li
authors.affiliation: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
authors.forename: Chunming
authors.initials: C
authors.lastname: Xu
authors.affiliation: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China;
authors.forename: Silin
authors.initials: S
authors.lastname: Zhong
authors.affiliation: Jilin Academy of Agricultural Sciences, Changchun 130033, China;
authors.forename: Xiuyun
authors.initials: X
authors.lastname: Lin
authors.affiliation: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
authors.forename: Jingjing
authors.initials: J
authors.lastname: Yang
authors.affiliation: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
authors.forename: Tianqi
authors.initials: T
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
authors.forename: Anzhi
authors.initials: A
authors.lastname: Yuliang
authors.affiliation: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
authors.forename: Ying
authors.initials: Y
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China;
authors.forename: Yun-Ru
authors.initials: YR
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Plant Genomics andNational Center for Plant Gene Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Cao
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720; and.
authors.forename: Assaf
authors.initials: A
authors.lastname: Zemach
authors.affiliation: Department of Crop and Soil Sciences,School of Molecular Biosciences, andCenter for Reproductive Biology, Washington State University, Pullman, WA 99164.
authors.forename: Sachin
authors.initials: S
authors.lastname: Rustgi
authors.affiliation: Department of Crop and Soil Sciences,School of Molecular Biosciences, andCenter for Reproductive Biology, Washington State University, Pullman, WA 99164 diter@wsu.edu baoliu@nenu.edu.cn.
authors.forename: Diter
authors.initials: D
authors.lastname: von Wettstein
authors.affiliation: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China; diter@wsu.edu baoliu@nenu.edu.cn.
authors.forename: Bao
authors.initials: B
authors.lastname: Liu
mesh_terms: D003596:Cytosine / Q000378:metabolism; D019175:DNA Methylation / Q000235:genetics*; D004251:DNA Transposable Elements / Q000235:genetics; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D018745:Genome, Plant / Q000235:genetics*; D008780:Methyltransferases / Q000235:genetics*; D009154:Mutation / Q000235:genetics*; D016366:Open Reading Frames / Q000235:genetics; D012275:Oryza / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D036226:Seedlings / Q000235:genetics* / Q000254:growth & development
chemical_list: D004251:DNA Transposable Elements; D010940:Plant Proteins; D018749:RNA, Plant; D003596:Cytosine; D008780:Methyltransferases
keywords: Oryza sativa L.; monocotyledons