- Oct 21, 2019
Date & Location: October 21, 2019, at 4p; Room 1200 Molecular Plant Sciences Building
Subject: The initiation of epigenetic silencing in plants
Host: Rob Last & Pengxiang Fang
About the Speaker
Institution: Donald Danforth Plant Science Center
Abstract: Plant cells have the ability to reliably ascertain which regions of their genome should be expressed (such as genes) and which regions should be transcriptionally repressed as constitutive heterochromatin. This affords them the ability to protect their genomes from parasitic forms of DNA, such as transposable elements, while this same defense mechanism is also often triggered to transgenes. This transcriptional silencing is epigenetic in nature, as once DNA methylation, histone modification and nucleosome compaction set in, they can be maintained over subsequent generations. The field of epigenetic silencing is replete with labs studying how transcriptional silencing is epigenetically maintained. On the other hand, the initiation of that silencing not understood. Understanding how transposable elements and transgenes are targeted for de novo initiation of silencing has significant implications for genome engineering and crop production.
Our data in the powerful model plant Arabidopsis demonstrates that initiation of transgene silencing is expression-dependent and utilizes all small RNA classes that function redundantly to guide the first round of DNA methylation. We find that a non-transcribing transposable element transgene fusion can avoid silencing altogether, demonstrating that the transcript or RNA Pol II transcription itself is the key trigger for the initiation of transgene silencing. I plan to present our ongoing work focused on understanding the molecular mechanisms needed to initiate epigenetic silencing.