December 16, 2020

3pm - 4pm
Please email santoniuk@mcdb.ucla.edu for Zoom link

Yan Xue
Postdoctoral Fellow - Jacobsen Lab

"Arabidopsis MORC proteins function in the establishment of RNA directed DNA methylation"

Abstract

The Microrchidia (MORC) family of ATPases are required for transposable element (TE) silencing and condensation of heterochromatin in both plants and animals, and C. elegans MORC-1 has been shown to topologically entrap and condense DNA. In Arabidopsis thaliana, mutation of MORCs has been shown to reactivate silent methylated genes and transposons and to decondense heterochromatic chromocenters, despite only minor changes in the maintenance of DNA methylation. Here we provide the first evidence localizing MORC proteins to specific regions of chromatin and find that MORC4 and MORC7 are closely co-localized with sites of RNA-directed DNA methylation (RdDM). We further show that MORC7, when tethered to DNA by a specific zinc finger can facilitate the establishment of RdDM. Finally, we show that MORCs are required for the efficient establishment of de novo RdDM when plants are transformed with an FWA transgene, even though morc mutations have no effect on the maintenance of preexisting methylation at FWA. We propose that MORCs act as de novo silencing factors in RdDM complexes by tethering these complexes to DNA to facilitate methylation establishment. These findings have implications for MORC protein function in a variety of other eukaryotic organisms.