Germ granules function as stress-responsive hubs to protect germ cell resilience
Biomolecular condensates are dynamic, membrane-less compartments that perform critical cellular functions in the adaptation to environmental stressors. Within germ cells, germ granules are specialized condensates essential for germ cell viability, genome defense, and epigenetic inheritance. Notably, environmental stressors such as heat and starvation can disrupt genome defense and epigenetic inheritance, yet germ cell viability is often preserved. How germ cells adapt to environmental stress and recover viability remains poorly understood. Here, we investigate the impact of heat stress on the biomolecular condensates of adult germ cells in C. elegans. Upon heat stress, we observe extensive remodeling of the germ granule compartments, including reduced enrichment of key genome defense and epigenetic inheritance factors. Adjacent to remodeled germ granules, stress granules and P-bodies robustly assemble, suggesting these distinct condensates may functionally interact during the stress response. Indeed, we find stress granule and P-body formation within germ cells largely requires germ granule assembly factors GLH-1/VASA and MIP-1. Furthermore, we show these germ granule assembly factors and stress granule factors GTBP-1/G3BP1 and TIAR-1/TIA1, are essential for recovery of germ cell viability after heat stress. Intriguingly, stress granule factor TIAR-1/ TIA1 localizes to germ granules with and without stress, indicating germ granules are poised for the stress response. Together, our results support a model in which germ granules function as stress-responsive hubs that reorganize RNA granule networks to promote germline resilience.