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Chromatin regulates expression of small RNAs to help maintain transposon methylome homeostasis in Arabidopsis

Authors
  • Papareddy, Ranjith K.1
  • Páldi, Katalin1
  • Paulraj, Subramanian1
  • Kao, Ping1
  • Lutzmayer, Stefan1
  • Nodine, Michael D.1
  • 1 Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, Vienna, 1030, Austria , Vienna (Austria)
Type
Published Article
Publication Date
Sep 17, 2020
Volume
21
Issue
1
Identifiers
DOI: 10.1186/s13059-020-02163-4
Source
Springer Nature
Keywords
License
Green

Abstract

BackgroundEukaryotic genomes are partitioned into euchromatic and heterochromatic domains to regulate gene expression and other fundamental cellular processes. However, chromatin is dynamic during growth and development and must be properly re-established after its decondensation. Small interfering RNAs (siRNAs) promote heterochromatin formation, but little is known about how chromatin regulates siRNA expression.ResultsWe demonstrate that thousands of transposable elements (TEs) produce exceptionally high levels of siRNAs in Arabidopsis thaliana embryos. TEs generate siRNAs throughout embryogenesis according to two distinct patterns depending on whether they are located in euchromatic or heterochromatic regions of the genome. siRNA precursors are transcribed in embryos, and siRNAs are required to direct the re-establishment of DNA methylation on TEs from which they are derived in the new generation. Decondensed chromatin also permits the production of 24-nt siRNAs from heterochromatic TEs during post-embryogenesis, and siRNA production from bipartite-classified TEs is controlled by their chromatin states.ConclusionsDecondensation of heterochromatin in response to developmental, and perhaps environmental, cues promotes the transcription and function of siRNAs in plants. Our results indicate that chromatin-mediated siRNA transcription provides a cell-autonomous homeostatic control mechanism to help reconstitute pre-existing chromatin states during growth and development including those that ensure silencing of TEs in the future germ line.

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