1887

Abstract

In the plant pathogen , nuclear integration of transgenic DNA sequences results in internuclear gene silencing of . Although silencing is regulated at the transcriptional level, it also affects transcription from other nuclei within heterokaryotic cells of the mycelium. Here we report experiments exploring the mechanism of internuclear gene silencing in . The DNA methylation inhibitor 5-azacytidine induced reversion of the -silenced state. Also, the histone deacetylase inhibitor trichostatin-A was able to reverse silencing. -expression levels returned to the silenced state when the inhibitors were removed except in non-transgenic -silenced strains that were generated via internuclear gene silencing, where expression was restored permanently. Therefore, -transgenic sequences are required to maintain the silenced state. Prolonged culture of non-transgenic -silenced strains resulted in gradual reactivation of gene expression. Nuclease digestion of -silenced and non-silenced nuclei showed that sequences in silenced nuclei were less rapidly degraded than non-silenced sequences. Bisulfite sequencing of the endogenous locus did not result in detection of any cytosine methylation. Our findings suggest that the -silenced state is based on chromatin remodelling.

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2008-05-01
2020-01-24
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