The Dynamic Composition of an Archetypal Plant Condensate Highlights a Tug-of-War between Condensates and Cell Vertex

Cellular condensates are usually ribonucleoprotein membrane-less assemblies that can shuttle between liquid or less fluid states. These phase transitions could impact a broad range of biological outcomes. Here, by developing proximity-biotinylation approaches, we unveil the composition of the condensate known as processing bodies (PBs) in the model plant Arabidopsis. We show that PBs comprise both conserved and dynamic networks with unexpected connections to membrane subdomains. We study further one of these networks and discover a cell vertex-defining module with membrane remodeling properties. This module functions through a liquid/solid-like phase transition that impacts growth. The underlying mechanism is developmentally regulated by a tug-of-war between PBs and the plasma membrane instructed by a phospho-switch. We thus provide a framework for the elucidation of condensates in plants and describe a growth module based on phase transitions of condensates at a membranous interface.