Transgene silencing by the host genome defense: implications for the evolution of epigenetic control mechanisms in plants and vertebrates

Matzke, M. A. and Mette, M. F. and Matzke, A. J. M. (2000) Transgene silencing by the host genome defense: implications for the evolution of epigenetic control mechanisms in plants and vertebrates. Plant Molecular Biology, 43. pp. 401-415.

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Increasing evidence supports the idea that various transgene silencing phenomena reflect the activity of diverse host defense responses that act ordinarily on natural foreign or parasitic sequences such as transposable elements, viroids, RNA and DNA viruses, and bacterial DNA. Transgenes or their transcripts can resemble these cellular invaders in a number of ways, thus making them targets of host protective reactions. At least two distinct host defense systems operate to silence transgenes. One acts at the genome level and is associated with de novo DNA methylation. A second line of defense operates post-transcriptionally and involves sequence-specific RNA degradation in the cytoplasm. Transgenes that are silenced as a consequence of the genome defense are revealing that de novo methylation can be cued by DNA-DNA or RNA-DNA interactions. These methylation signals can be interpreted in the context of transposable elements or their transcripts. During evolution, as transposable elements accumulated in plant and vertebrate genomes and as they invaded flanking regions of genes, the genome defense was possibly recruited to establish global epigenetic mechanisms to regulate gene expression. Transposons integrated into promoters of host genes could conceivably change expression patterns and attract methylation, thus imposing on endogenous genes the type of epigenetic regulation associated with the genome defense. This recruitment process might have been particularly effective in the polyploid genomes of plants and early vertebrates. Duplication of the entire genome in polyploids buffers against insertional mutagenesis by transposable elements and permits their infiltration into individual copies of duplicated genes.

Item Type: Article
Additional Information: We thank M. Wassenegger and W. Aufsatz for comments on the manuscript. Work in our lab is supported by the Austrian Fonds zur Förderung der wissenschaftlichen Forschung (Z21-MED) and the European Union (Contract BIO4-CT96-0253).
Uncontrolled Keywords: DNA methylation, epigenetic silencing, genome evolution, polyploidy, transgenes, transposable elements
Author Affiliation: Institute of Molecular Biology, Austrian Academy of Sciences, Billrothstrasse 11, 5020 Salzburg, Austria
Subjects: Crop Improvement > Genetics/Genomics
Divisions: General
Depositing User: Mr Siva Shankar
Date Deposited: 27 Apr 2012 08:10
Last Modified: 27 Apr 2012 08:10

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