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

EMBO J. 1994 May 1;13(9):2084-8. doi: 10.1002/j.1460-2075.1994.tb06483.x.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Cytosine / metabolism*
  • DNA / metabolism*
  • Methylation
  • Methyltransferases / metabolism
  • Molecular Sequence Data
  • Plants, Genetically Modified
  • Polymerase Chain Reaction
  • Promoter Regions, Genetic
  • Substrate Specificity

Substances

  • Cytosine
  • DNA
  • Methyltransferases