Investigating the Involvement of the Unfolded Protein Response in Bread Wheat Priming and Adaptation to Heat Stress

The temperature increase caused by climate change induces the accumulation of misfolded proteins in the endoplasmic reticulum. To restore protein homeostasis, plants activate the Unfolded Protein Response (UPR). In this study, the involvement of UPR in improving severe heat stress tolerance through molecular priming was explored in Triticum aestivum. The UPR activation and turn-off dynamics were determined. Moreover, the importance of the TaIRE1/TabZIP60 induction branch in the response to ER stress was assessed using TaIRE1 knockout mutants. The results indicate that plants primed with dithiothreitol exhibit a faster and higher TabZIP60 splicing response to temperature stress than unprimed plants. This suggests that UPR induction by TaIRE1/TabZIP60 is a finely regulated adaptive mechanism that alleviates the ER stress caused by heat increase. Moreover, UPR was defined as a molecular primer insofar as it participates in enhancing the stress response. Furthermore, the development and photosynthetic capacity of TaIRE1 mutants were negatively affected, resulting in increased cellular damage in response to ER stress. The TaIRE1/TabZIP60 induction branch, crucial for ER stress recovery, does not appear to be fully compensated by TabZIP28. This study provides new insights into the role of the UPR in response to abiotic stresses and proposes potential strategies to improve wheat heat tolerance.