Abstract
SummaryEstablishing the embryonic body plan of multicellular organisms relies on precisely orchestrated cell divisions coupled with pattern formation, which, in animals, are regulated by Polycomb group (PcG) proteins. The conserved Polycomb Repressive Complex 2 (PRC2) mediates H3K27 trimethylation and comes in different flavors in Arabidopsis. The PRC2 catalytic subunit MEDEA is required for seed development; however, a role for PRC2 in embryonic patterning has been dismissed. Here, we demonstrate that embryos derived from medea eggs abort because MEDEA is required for patterning and cell lineage determination in the early embryo. Similar to PcG proteins in mammals, MEDEA regulates embryonic patterning and growth by controlling cell-cycle progression through repression of CYCD1;1, which encodes a core cell-cycle component. Thus, Arabidopsis embryogenesis is epigenetically regulated by PcG proteins, revealing that the PRC2-dependent modulation of cell-cycle progression was independently recruited to control embryonic cell proliferation and patterning in animals and plants.
Highlights
A fundamental question in developmental biology is how cells acquire and maintain their identity over time
Establishing the embryonic body plan of multicellular organisms relies on precisely orchestrated cell divisions coupled with pattern formation, which, in animals, are regulated by Polycomb group (PcG) proteins
The Polycomb Repressive Complex 2 (PRC2) catalytic subunit MEDEA is required for seed development; a role for PRC2 in embryonic patterning has been dismissed
Summary
A fundamental question in developmental biology is how cells acquire and maintain their identity over time. While mutations affecting PRC2 subunits lead to embryo lethality in animals (Faust et al, 1995; O’Carroll et al, 2001; Oktaba et al, 2008; Pasini et al, 2004; Grosswendt et al, 2020), plants lacking PRC2 components do not show severe embryonic phenotypes and most produce viable offspring (Bouyer et al, 2011; Chanvivattana et al, 2004; Kinoshita et al, 2001) This is because plants possess several different PRC2 complexes: EMF-PRC2 controls aspects of vegetative development; VRN-PRC2 regulates flowering time and the plants’ response to vernalization; and FIS-PRC2 has a specific role in reproduction, in female gametophyte, endosperm, and seed development (Grossniklaus and Paro, 2014; Hugues et al, 2020).
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