The methylation patterns of the MET1 gene in organs of Arabidopsis thaliana were 
studied by Southern blot hybridization of DNA samples hydrolyzed with 
differentially methylation-sensitive restriction endonucleases. A highly 
methylated on internal cytosine residue CCGG site was found 1.5 kb upstream of 
the gene, whereas CCGG sites located in more proximal parts of the 5'-flanking 
region and the gene itself are essentially unmethylated. This methylation 
pattern was observed in different organs of plants belonging to two different 
ecotypes as well as in different transgenic plant lines. The methylation level 
ofa CCGG site in exon 3 (2.1 kb from the gene's 5'-end) occurred to be variable 
between different transgenic plant lines and two ecotypes studied. Transcription 
levels of the MET1 gene vary slightly in organs of wild-type plants without any 
obvious correlation with its methylation. The transgenic antisense MET1 
constructs expressed in plant genome do affect both MET1 methylation and its 
transcription but again without any obvious correlation. The comparative 
investigation of transcription levels of different genes of cytosine DNA 
methyltransferase family MET (MET1, MET2a, MET2b, MET3) and their methylation 
patterns shows that there may exist some mechanisms defending the most actively 
transcribed gene MET1 of this family from methylation mediated silencing. In 
contrast to DRM2 gene we could not find any adenine methylated GATC sites in the 
MET1 gene.