Abiotic-stress induces demethylation and transcriptional activation of a gene encoding a glycerophosphodiesterase-like protein in tobacco plants.
To examine the relationship between gene expression and DNA methylation, transcriptionally activated genes were screened in hypomethylated transgenic tobacco plants expressing an anti-DNA methyltransferase sequence. Among 16 genes initially identified, one clone was found to encode a glycerophosphodiesterase-like protein (NtGPDL), earlier reported to be responsive to aluminium stress. When detached leaves from wild type tobacco plants were treated with aluminium, NtGPDL transcripts were induced within 6 h, and corresponding genomic loci were demethylated at CCGG sites within 1 h. Direct bisulfite methylation mapping revealed that CG sites in coding regions were selectively demethylated, and that promoter regions were totally unmethylated regardless of the stress. Salt and low temperature treatments also induced similar demethylation patterns. Such effects could be attributable to oxidative stress, since reactive oxygen species generated by paraquat efficiently induced the same pattern of demethylation at coding regions. Pathogen infection induced neither transcripts nor genomic demethylation. These results suggested a close correlation between methylation and expression of NtGPDL upon abiotic stresses with a cause-effect relationship. Since DNA methylation is linked to histone modification, it is conceivable that demethylation at coding regions might induce alteration of chromatin structure, thereby enhancing transcription. We propose that environmental responses of plants are partly mediated through active alteration of the DNA methylation status.
Choi
Chang-Sun
CS
Research and Education Center for Genetic Information, Nara Institute of Science and Technology, Nara, Japan.
Sano
Hiroshi
H
D044503:5-Methylcytosine / Q000378:metabolism; D000535:Aluminum / Q000494:pharmacology; D000595:Amino Acid Sequence; D001483:Base Sequence; D019175:DNA Methylation; D020690:GTPase-Activating Proteins / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D018384:Oxidative Stress; D010727:Phosphoric Diester Hydrolases / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics*; D015533:Transcriptional Activation
D020690:GTPase-Activating Proteins; D010940:Plant Proteins; D044503:5-Methylcytosine; D000535:Aluminum; D010727:Phosphoric Diester Hydrolases