Expanding knowledge of the R ubisco kinetics variability in plant species: environmental and evolutionary trends

The present study characterizes the kinetic properties of ribulose‐1,5‐bisphosphate carboxylase/oxygenase ( R ubisco) from 28 terrestrial plant species, representing different phylogenetic lineages, environmental adaptations and photosynthetic mechanisms. Our findings confirm that past atmospheric CO 2 / O 2 ratio changes and present environmental pressures have influenced R ubisco kinetics. One evolutionary adaptation to a decreasing atmospheric CO 2 / O 2 ratio has been an increase in the affinity of R ubisco for CO 2 ( K c falling), and a consequent decrease in the velocity of carboxylation ( k cat c ), which in turn has been ameliorated by an increase in the proportion of leaf protein accounted by R ubisco. The trade‐off between K c and k cat c was not universal among the species studied and deviations from this relationship occur in extant forms of R ubisco. In species adapted to particular environments, including carnivorous plants, crassulacean acid metabolism species and C 3 plants from aquatic and arid habitats, R ubisco has evolved towards increased efficiency, as demonstrated by a higher k cat c / K c ratio. This variability in kinetics was related to the amino acid sequence of the R ubisco large subunit. Phylogenetic analysis identified 13 residues under positive selection during evolution towards specific R ubisco kinetic parameters. This crucial information provides candidate amino acid replacements, which could be implemented to optimize crop photosynthesis under a range of environmental conditions.