PT - JOURNAL ARTICLE AU - M. Sankaranarayanan AU - Ryan J. Emenecker AU - Marcus Jahnel AU - Irmela R. E. A. Trussina AU - Matt Wayland AU - Simon Alberti AU - Alex S. Holehouse AU - Timothy T. Weil TI - The arrested state of processing bodies supports mRNA regulation in early development AID - 10.1101/2021.03.16.435709 DP - 2021 Jan 01 TA - bioRxiv PG - 2021.03.16.435709 4099 - http://biorxiv.org/content/early/2021/03/16/2021.03.16.435709.short 4100 - http://biorxiv.org/content/early/2021/03/16/2021.03.16.435709.full AB - Biomolecular condensates that form via liquid-liquid phase separation can exhibit diverse physical states. Despite considerable progress, the relevance of condensate physical states for in vivo biological function remains limited. Here, we investigated the physical properties of in vivo processing bodies (P bodies) and their impact on mRNA storage in mature Drosophila oocytes. We show that the conserved DEAD-box RNA helicase Me31B forms P body condensates which adopt a less dynamic, arrested physical state. We demonstrate that structurally distinct proteins and hydrophobic and electrostatic interactions, together with RNA and intrinsically disordered regions, regulate the physical properties of P bodies. Finally, using live imaging, we show that the arrested state of P bodies is required to prevent the premature release of bicoid (bcd) mRNA, a body axis determinant, and that P body dissolution leads to bcd release. Together, this work establishes a role for arrested states of biomolecular condensates in regulating cellular function in a developing organism.Competing Interest StatementThe authors have declared no competing interest.