J Integr Plant Biol ›› 2011, Vol. 53 ›› Issue (10): 814-823.DOI: 10.1111/j.1744-7909.2011.01070.x

Special Issue: Rice Genomics and Agriculture

• Plant-environmental Interactions • Previous Articles     Next Articles

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

Yuan Li1†, Qiong Xia1†, Hongping Kou2, Dan Wang2, Xiuyun Lin3, Ying Wu1, Chunming Xu1, Shaocheng Xing3 and Bao Liu1*   

  1. 1Key Laboratory of Molecular Epigenetics of MOE and The Institute of Genetics & Cytology, Northeast Normal University, Changchun 130024, China
    2Department of Agronomy, Jilin Agricultural University, Changchun 130118, China
    3Center of Agribiotechnology, Jilin Academy of Agricultural Sciences, Changchun 130033, China
  • Received:2011-03-14 Accepted:2011-07-13 Published:2011-07-21
  • About author:*Corresponding author. Tel: +86 431 8509 9822; Fax: +86 431 8509 9822; E-mail: baoliu@nenu.edu.cn

Abstract:

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.

Keywords: DNA methylation; Magnaporthe grisea; blast-resistance; induced Pib expression.

Li Y, Xia Q, Kou H, Wang D, Lin X, Wu Y, Xu C, Xing S and Liu B (2011) Induced Pib expression and resistance to Magnaporthe grisea are compromised by cytosine demethylation at critical promoter regions in rice. J. Integr. Plant Biol. 53(10), 814-823.

Key words: blast-resistance, DNA methylation, induced Pib expression, Magnaporthe grisea.

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