Sequence-specific hypomethylation of the tobacco genome induced with dihydroxypropyladenine, ethionine and 5-azacytidine.
Higher plant DNA is methylated at CG and CNG targets. In this study we have investigated the tobacco methylation system in tissue culture using the methylation inhibitors 5-azacytidine (5-azaC), dihydroxypropyladenine (DHPA) and ethionine (Ethi), and methylation-sensitive restriction endonucleases HpaII, MspI, HhaI, EcoRII, ScrFI, and Fnu4HI. Surprisingly, CAG/CTG sequences, contrary to CG doublets and CCG/CGG triplets, appeared to be refractory to the inhibitory effect of 5-azaC. Thus 5-azaC cannot be considered a general inhibitor of DNA methylation in tobacco cells. On the other hand, DHPA, the inhibitor of S-adenosylhomocysteine (SAH) hydrolase, and Ethi caused hypomethylation of both CAG/CTG and CCG/CGG triplets but not of the CG doublets. The sensitivity of triplet-specific methylation to the inhibition of SAH hydrolase suggests the possibility that plant-specific DNA methylation at CNG targets might be modulated by alterations of the SAH/S-Adenosylmethionine ratio in plant cells.
Kovarík
A
A
Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno.
Koukalová
B
B
Holý
A
A
Bezdĕk
M
M
D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D043383:Adenosylhomocysteinase; D001374:Azacitidine / Q000494:pharmacology*; D002478:Cells, Cultured; D018744:DNA, Plant / Q000378:metabolism*; D015257:DNA-Cytosine Methylases / Q000378:metabolism; D015252:Deoxyribonucleases, Type II Site-Specific; D005001:Ethionine / Q000494:pharmacology*; D018745:Genome, Plant; D006867:Hydrolases / Q000037:antagonists & inhibitors; D008745:Methylation / Q000187:drug effects; D010947:Plants, Toxic; D014026:Nicotiana / Q000235:genetics*
D018744:DNA, Plant; C016391:9-(2,3-dihydroxypropyl)adenine; D015257:DNA-Cytosine Methylases; D006867:Hydrolases; D015252:Deoxyribonucleases, Type II Site-Specific; D043383:Adenosylhomocysteinase; D000225:Adenine; D001374:Azacitidine; D005001:Ethionine