Wheat CHIP E3 ubiquitin ligase, TaCEU, forms a complex with TaCHSP70 to regulate targeted proteins, enhancing thermotolerance in transgenic Arabidopsis

Heat stress significantly impacts plant growth and productivity by causing protein misfolding, oxidative damage, and disruptions in cellular homeostasis. This stress is particularly critical during flowering and grain-filling stages, where even brief exposure to high temperatures can result in severe yield losses. Plants have evolved complex molecular mechanisms to mitigate heat stress, including the activation of heat shock proteins and the ubiquitin-proteasome system to maintain protein quality and cellular function. Understanding these processes is essential for breeding stress-resistant crops capable of adapting to climate change. In this study, we characterized TaCEU, a wheat carboxy-terminal Hsp70-interacting protein and E3 ubiquitin ligase, with a conserved structure across plant species. TaCEU is highly upregulated under heat and ABA stress and plays a pivotal role in maintaining protein homeostasis during heat stress. We confirmed TaCEU's role as an E3 ligase through in vitro ubiquitination assays, demonstrating its ability to form polyubiquitin chains. Subcellular localization studies confirmed TaCEU's presence in the nucleus and plasma membrane, suggesting functional versatility. Interaction studies identified TaAP and TaCHSP70 as key partners, with TaCEU and TaCHSP70 collaboratively targeting TaAP for degradation via the UPS proteasome system. Functional analysis of TaCEU-overexpressing Arabidopsis revealed enhanced thermotolerance, including increased root length, fresh weight, and antioxidant enzyme activity under heat stress. Transcript analysis further indicated the upregulation of heat stress-responsive genes, highlighting TaCEU's critical role in stress adaptation. These findings establish TaCEU as a key regulator of thermotolerance and protein homeostasis. TaCEU regulates protein stability and enhancing thermotolerance, making it a promising target for developing heat-resistant crops to address the challenges of climate change.