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      Site specificity of the Arabidopsis METI DNA methyltransferase demonstrated through hypermethylation of the superman locus.

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          Abstract

          Plants with low levels of DNA methylation show a range of developmental abnormalities including homeotic transformation of floral organs. Two independent DNA METHYLTRANSFERASEI (METI) antisense transformants with low levels of DNA methylation had flowers with increased numbers of stamens which resembled flowers seen on the loss-of-function superman (sup) mutant plants and on transgenic plants that ectopically express APETALA3 (AP3). These METI antisense plants have both increased and decreased methylation in and around the sup gene, compared with untransformed controls. DNA from the antisense plants was demethylated at least 4 kb upstream of the sup gene, while there was dense methylation around the start of transcription and within the coding region of this gene; these regions were unmethylated in control DNA. Methylation within the sup gene was correlated with an absence of SUP transcripts. The pattern and density of methylation was heterogeneous among different DNA molecules from the same plant, with some molecules being completely unmethylated. Methylcytosine occurred in asymmetric sites and in symmetric CpA/TpG but rarely in CpG dinucleotides in the antisense plants. In contrast, segregants lacking the METI antisense construct and epimutants with a hypermethylated allele of sup (clark kent 3), both of which have active METI genes, showed a higher frequency of methylation of CpG dinucleotides and of asymmetric cytosines. We conclude that METI is the predominant CpG methyltransferase and directly or indirectly affects asymmetric methylation.

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          Author and article information

          Journal
          Plant Mol Biol
          Plant molecular biology
          Springer Science and Business Media LLC
          0167-4412
          0167-4412
          May 2001
          : 46
          : 2
          Affiliations
          [1 ] CSIRO, Plant Industry, Canberra, Australia.
          Article
          10.1023/a:1010636222327
          11442057
          dbc4e68f-d58d-4fd0-a5bd-1fc582c7c023
          History

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