Stress Granule-Associated ZmCTU2 Confers Thermotolerance in Maize via Coordinated Regulation of Proteostasis and ROS Homeostasis.

The escalating global temperatures and intensifying heat stress events pose significant threats to maize productivity worldwide. Uncovering key thermotolerance genes and their functional mechanisms is thus critical for developing climate-resilient crops. Here, we report that ZmCTU2, a cytoplasmic tRNA thiolation factor, acts as a central regulator of heat tolerance in maize. Expression of ZmCTU2 correlates positively with kernel-setting under high temperatures. Overexpression of ZmCTU2 confers enhanced thermotolerance at both seedling and adult stages, improving survival and field yield under heat stress, whereas loss-of-function mutants of ZmCTU2 or its partner ZmCTU1 display severe seed developmental defects and lethality. Mechanistically, ZmCTU2 translocates to stress granules under thermal stress, where it recruits ZmCTU1 and ROS-scavenging peroxidases, shielding them from degradation. This dual recruitment facilitates synergistic protective responses: maintenance of tRNA thiolation to ensure translational fidelity, and stabilisation of antioxidative enzymes to bolster redox homeostasis. Our study identifies ZmCTU2 as a scaffold protein within stress granules that coordinates proteostatic and antioxidative pathways under heat stress, providing a valuable genetic resource for engineering thermotolerant maize.