Abstract
Paramutation is an allele-dependent transfer of epigenetic information, which results in the heritable silencing of one allele by another. Paramutation at the b1 locus in maize is mediated by unique tandem repeats that communicate in trans to establish and maintain meiotically heritable transcriptional silencing. The mop1 (mediator of paramutation1) gene is required for paramutation, and mop1 mutations reactivate silenced Mutator elements. Plants carrying mutations in the mop1 gene also stochastically exhibit pleiotropic developmental phenotypes. Here we report the map-based cloning of mop1, an RNA-dependent RNA polymerase gene (RDRP), most similar to the RDRP in plants that is associated with the production of short interfering RNA (siRNA) targeting chromatin. Nuclear run-on assays reveal that the tandem repeats required for b1 paramutation are transcribed from both strands, but siRNAs were not detected. We propose that the mop1 RDRP is required to maintain a threshold level of repeat RNA, which functions in trans to establish and maintain the heritable chromatin states associated with paramutation.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 295-298 |
| Number of pages | 4 |
| Journal | Nature |
| Volume | 442 |
| Issue number | 7100 |
| DOIs | |
| State | Published - Jul 20 2006 |
Bibliographical note
Funding Information:Acknowledgements We thank R. Wing and Arizona Genomics Institute scientists H. R. Kim, T. Rambo Mueller and F. Wei for sequencing and finishing the BAC clones; R. Jorgensen, C. Napoli and K. Gendler for performing the alignments and phylogenetic analyses; G. McCarthy and J. Bennetzen for help with the Bac-Breaker retroelement analysis of the BAC sequences; J. Gardiner for providing sequences for a mapping marker; and H. Basinger for technical assistance with the nuclear run-on assays. This work was supported by grants to V.L.C. from the National Science Foundation (NSF) and the National Institutes of Health; M.A. received a sabbatical supplement from the NSF. K.S., a student in the Undergraduate Biology Research Program, was supported in part by the Howard Hughes Medical Institute.