Germ granule higher-order organization coordinates their different functions

Most RNP condensates are composed of heterogeneous immiscible phases. However, how this multiphase organization contributes to their biological functions remains largely unexplored. Drosophila germ granules, a class of RNP condensates, are the site of mRNA storage and translational activation. Here, using super-resolution microscopy and single-molecule imaging approaches, we show that germ granules have a biphasic organization and that translation occurs in the outer phase and at the surface of the granules. The localization, directionality and compaction of mRNAs within the granule depend on their translation status, translated mRNAs being enriched in the outer phase with their 5’end oriented towards the surface. Altering germ granule biphasic organization represses translation. These findings demonstrate the importance of RNA granule architecture in organizing different functions, highlighting the functional compartmentalization of RNA granules and the key role of higher-order organization.