Wheat is the most widely grown crop in the world, it provides 20% of the daily protein and calories. CO2 assimilation during photosynthesis is the primary determinant of plant biomass production. Rubisco plays a key role in CO2 assimilation, but is not optimally poised for crop productivity and additionally, it is prone to inhibition by unproductive binding of sugar-phosphates that lock active sites in a closed conformation. Rubisco activase (Rca) is a catalytic chaperone that remodels the active site, promotes the release of inhibitors and restores catalytic competence to Rubisco. Rca activity and its consequent effect on Rubisco activation and photosynthesis are modulated by changes to the chloroplast environment induced by fluctuations in light levels that reach the leaf, including redox status and ADP/ATP ratio. Here, we set out to investigate the regulatory properties of the three Rca isoforms present in wheat. The results show that the wheat Rca isoforms differ in their regulatory properties and that amino acid changes in the C-terminal influence ADP sensitivity. Advances in the understanding of Rubisco regulation will aid efforts to improve the efficiency of photosynthetic CO2 assimilation.
