PSKR1-mediated phosphorylation of βCA2 activates its carbonic anhydrase activity to integrate CO2 and heat signals for enhanced thermotolerance in tomato.

Plants are increasingly subjected to concurrent heat stress and elevated CO2; however, how they perceive and integrate these combined stresses remains poorly understood. Here, we identify the β-carbonic anhydrase βCA2 as a central signaling hub in tomato that decodes these combined cues. We demonstrate that βCA2 physically interacts with the receptor kinase PSKR1 at the plasma membrane and that PSKR1-mediated phosphorylation of βCA2 is significantly enhanced under simultaneous elevated CO2 and heat stress. We further identify Ser231 as the crucial phosphorylation site on βCA2. Phosphorylation at Ser231 activates βCA2 and is essential for the accumulation of phosphatidic acid, a lipid signaling molecule that protects plants from heat damage. These findings provide new insight into the complex integration of environmental stress signals through βCA2 and underscore the critical role of CO2-heat interactions in plant stress responses. Our work not only deepens understanding of plant adaptation to climate change but also provides potential targets for developing climate-resilient crops.