Heat stress promotes Arabidopsis AGO1 phase separation and association with stress granule components

A new article by Blagojevic, Baldrich, and Schiaffini et al. reveals that Arabidopsis ARGONAUTE1 (AGO1) protein, a pivotal agent in miRNA and siRNA-mediated gene silencing associated with the rough endoplasmic reticulum, dynamically localizes within stress granule components during heat stress (HS). This relocalization does not require SUPPRESSOR OF GENE SILENCING 3 (SGS3) and includes interactions with P-bodies and RNA decay components, forming a unique HS-induced AGO1 interactome. Moreover, even a short period of HS at 37°C results in only limited changes to small RNA (sRNA) accumulation and their loading into AGO1, indicating the resilience of AGO1’s silencing capabilities under HS. A significant finding is that AGO1 undergoes liquid-liquid phase separation through its N-terminal Poly-Q domain, which may contribute to its protective aggregation in cytosolic condensates. This study enhances our understanding of the molecular responses to HS in plants, highlighting the robust nature of AGO1 and its gene regulatory functions during environmental stress. (Summary by Yueh Cho @YuehCho1984) iScience. 10.1016/j.isci.2024.109151