Induced Pib Expression and Resistance to Magnaporthe grisea are Compromised by Cytosine Demethylation at Critical Promoter Regions in Rice  

作　　者：Yuan Li Qiong Xia Hongping Kou Dan Wang Xiuyun Lin Ying Wu Chunming Xu Shaochen Xing Bao Liu 

机构地区：[1]Key Laboratory of Molecular Epigenetics of MOE and The Institute of Genetics ＆ Cytology, Northeast Normal University, Changchun 130024, China [2]Department of Agronomy, Jilin Agricultural University, Changchun 130118, China [3]Center of Agribiotechnology, Jilin Academy of Agricultural Sciences, Changchun 130033, China

出　　处：《Journal of Integrative Plant Biology》2011年第10期814-823,共10页植物学报（英文版）

基　　金：supported by the State Key Basic Research and Development Plan of China(2011CB100205);the Program for Introducing Talents to Universities(B07017)

摘　　要：Pib is a well-characterized rice blast-resistance gene belonging to the nucleotide binding site （NBS） and leucine-rich repeat （LRR） superfamily. Expression of Pib was low under non-challenged conditions, but strongly induced by the blast-causing fungal pathogen Magnaporthe grisea, thereby conferring resistance to the pathogen. It is generally established that cytosine methylation of the promoter-region often plays a repressive role in modulating expression of the gene in question. We report here that two critical regions of the Pib promoter were heavily CG cytosine-methylated in both cultivars studied. Surprisingly, induced expression of Pib by M. grisea infection did not entail its promoter demethylation, and partial demethylation by 5-azacytidine-treatment actually reduced Pib expression relative to wild- type plants. Accordingly, the blast disease-resistance was compromised in the 5＇-azaC-treated plants relative to wild-type. In contrast, the disease susceptibility was not affected by the 5＇-azaC treatment in another two rice cultivars that did not contain the Pib gene, ruling out effects of other R genes and non.specific genotoxic effects by the drug-treatment as a cause for the compromised Pib-conditioned blast-resistance. Taken together, our results suggest that promoter DNA methylation plays a novel enhancing role in conditioning high-level of induced expression of the Pib gene in times of M. grisea infection, and its conferred resistance to the pathogen.Pib is a well-characterized rice blast-resistance gene belonging to the nucleotide binding site （NBS） and leucine-rich repeat （LRR） superfamily. Expression of Pib was low under non-challenged conditions, but strongly induced by the blast-causing fungal pathogen Magnaporthe grisea, thereby conferring resistance to the pathogen. It is generally established that cytosine methylation of the promoter-region often plays a repressive role in modulating expression of the gene in question. We report here that two critical regions of the Pib promoter were heavily CG cytosine-methylated in both cultivars studied. Surprisingly, induced expression of Pib by M. grisea infection did not entail its promoter demethylation, and partial demethylation by 5-azacytidine-treatment actually reduced Pib expression relative to wild- type plants. Accordingly, the blast disease-resistance was compromised in the 5＇-azaC-treated plants relative to wild-type. In contrast, the disease susceptibility was not affected by the 5＇-azaC treatment in another two rice cultivars that did not contain the Pib gene, ruling out effects of other R genes and non.specific genotoxic effects by the drug-treatment as a cause for the compromised Pib-conditioned blast-resistance. Taken together, our results suggest that promoter DNA methylation plays a novel enhancing role in conditioning high-level of induced expression of the Pib gene in times of M. grisea infection, and its conferred resistance to the pathogen.

关 键 词：DNA methylation Magnaporthe grisea blast-resistance induced Pib expression. 

分 类 号：S511[农业科学—作物学] O627.4[理学—有机化学]