Evidence for cytosine methylation of non‐symmetrical sequences in transgenic Petunia hybrida

• Published in: The EMBO journal 1994-05, Vol.13 (9), p.2084-2088
• Main Authors: Meyer, P., Niedenhof, I., Lohuis, M.
• Format: Article
• Language: English
• Subjects: Base Sequence; Biological and medical sciences; Cytosine - metabolism; DNA - metabolism; Fundamental and applied biological sciences. Psychology; Genes. Genome; Methylation; Methyltransferases - metabolism; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Petunia hybrida; Plants, Genetically Modified; Polymerase Chain Reaction; Promoter Regions, Genetic; Substrate Specificity
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1002/j.1460-2075.1994.tb06483.x

A considerable proportion of cytosine residues in plants are methylated at carbon 5. According to a well‐accepted rule, cytosine methylation is confined to symmetrical sequences such as CpG and CpNpG, which provide the signal for faithful transmission of symmetrical methylation patterns by maintenance methylase. Using a genomic sequencing technique, we have analysed cytosine methylation patterns within a hypermethylated and a hypomethylated state of a transgene in Petunia hybrida. Examination of a part of the transgene promoter revealed that in both states m5C residues located within non‐symmetrical sequences could be detected. Non‐symmetrical C residues in the two states were methylated at frequencies of 5.9 and 31.9%, respectively. Methylation appeared to be distributed heterogeneously, but some DNA regions were more intensively methylated than others. Our results show that at least in a transgene, a heterogeneous methylation pattern, which does not depend on symmetry of target sequences, can be established and conserved.