Mutation of a major CG methylase in rice causes genome-wide hypomethylation, dysregulated genome expression, and seedling lethality.
Lanjuan Hu, Ning Li, Chunming Xu, Silin Zhong, Xiuyun Lin, Jingjing Yang, Tianqi Zhou, Anzhi Yuliang, Ying Wu, Yun-Ru Chen, Xiaofeng Cao, Assaf Zemach, Sachin Rustgi, Diter von Wettstein, Bao Liu
Author Information
Lanjuan Hu: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
Ning Li: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
Chunming Xu: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
Silin Zhong: 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;
Xiuyun Lin: Jilin Academy of Agricultural Sciences, Changchun 130033, China;
Jingjing Yang: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
Tianqi Zhou: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
Anzhi Yuliang: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
Ying Wu: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China;
Yun-Ru Chen: State Key Laboratory of Agrobiotechnology, School of Life Sciences, The Chinese University of Hong Kong, Hong Kong, China;
Xiaofeng Cao: 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;
Assaf Zemach: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720; and.
Sachin Rustgi: Department of Crop and Soil Sciences,School of Molecular Biosciences, andCenter for Reproductive Biology, Washington State University, Pullman, WA 99164.
Diter von Wettstein: 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.
Bao Liu: Key Laboratory of Molecular Epigenetics of the Ministry of Education, Northeast Normal University, Changchun 130024, China; diter@wsu.edu baoliu@nenu.edu.cn.
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.
