Rubisco activase is an ATP-dependent chaperone that facilitates dissociation of inhibitory sugar phosphates from the catalytic sites of Rubisco during photosynthesis. In Arabidopsis, Rubisco activase is negatively regulated by dark-dependent phosphorylation of Thr78. However, it is not clear whether this mechanism is relevant outside of Arabidopsis. To address this knowledge gap, researchers at the Center for Advanced Bioenergy and Bioproducts Innovation (CABBI) investigated the prevalence of Thr78 in Rubisco activase across 91 plant species. Their results suggest that despite conservation of Thr78 in Rubisco activase from a wide range of species, a regulatory role for phosphorylation at this site is more limited. This provides a case study for how variation in post-translational regulation can amplify functional divergence across the phylogeny of plants beyond what is explained by sequence variation in a metabolically important protein.
