Comptes rendus des séances de la Société de biologie et de ses filiales, 191: 161 (1997)
Analysis of epigenetic changes in (trans)gene expression
Christophe Béclin, Stéphanie Boutet, Hervé Vaucheret

Isogenic seedlings derived from a transgenic tobacco line carrying a 35S-uidA reporter transgene are shown. The expression of the transgene can be uniform and stable (left) or variegated due to stochastic silencing (right).

Summary

In eukaryotes, transgenes may undergo epigenetic silencing, i. e. heritable alterations in gene expression that can not be explained by changes in DNA sequence. When the introduced transgenes are homologous to host endogenous genes, gene silencing can affect both host and transgene expression. Gene silencing can occur either at the transcriptional level (i. e. transcription is blocked) or at the post-transcriptional level (i. e. RNA turner-over is increased).

The study of transgene silencing phenomena provides the opportunity to understand underlying natural mechanisms of plant defence acting at the DNA or RNA level to stabilize the genome and to combat invading pathogens. Transcriptional silencing may recruit cellular components acting against invading DNA that integrates into the genome, while post-transcriptional silencing may recruit cellular components acting against invading DNA or RNA that replicate extra-chromosomally in the nucleus and the cytoplasm respectively. Our group aims to analyse the genetic and molecular basis of gene silencing and to define strategies for preventing transgenes from silencing.

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