ABSTRACT Rubisco activase mediates the activation of Rubisco, the key photosynthetic CO 2 ‐fixing enzyme, and plays a crucial role in regulating photosynthesis and plant growth. Rubisco activase restores catalytic competence to Rubisco active sites by promoting the release of inhibitors in an ATP‐dependent manner. The present study analyzed the role of Rubisco activase in the photosynthetic response to fluctuating light under future high CO 2 conditions using transgenic rice plants that expressed different amounts of Rubisco activase. Under both low CO 2 (200 μmol mol −1 ) and high CO 2 (800 μmol mol −1 ) concentrations, overexpression of Rubisco activase resulted in a faster rate of Rubisco activation upon irradiation, leading to faster photosynthetic induction and greater photosynthetic response to long‐term fluctuating light conditions. In addition, the transgenic plants overexpressing Rubisco activase showed improved water use efficiency under long‐term fluctuating light conditions compared with wild‐type plants. Finally, under high CO 2 conditions, the overexpression of Rubisco activase resulted in improvement in plant growth under fluctuating light conditions, whereas the plant growth under constant light was similar among genotypes. The results of this study showed that Rubisco activase plays a substantial role in the response to the natural dynamic light environment under future high CO 2 concentrations.
Yamori et al. (2026) studied this question.