Rubisco substitutions predicted to enhance crop performance through carbon uptake modelling

Improving the performance of the CO(2)-fixing enzyme Rubisco is among the targets for increasing crop yields. Here, Earth system model (ESM) representations of canopy C(3) and C(4) photosynthesis were combined with species-specific Rubisco parameters to quantify the consequences of bioengineering foreign Rubiscos into C(3) and C(4) crops under field conditions. The ‘two big leaf’ (sunlit/shaded) model for canopy photosynthesis was used together with species-specific Rubisco kinetic parameters including maximum rate (K(cat)), Michaelis–Menten constant for CO(2) at ambient atmospheric O(2) (K(c)(21%O2)), specificity for CO(2) to O(2) (S(c/o)), and associated heat activation (H(a)) values. Canopy-scale consequences of replacing native Rubiscos in wheat, maize, and sugar beet with foreign enzymes from 27 species were modelled using data from Ameriflux and Fluxnet databases. Variation among the included Rubisco kinetics differentially affected modelled carbon uptake rates, and Rubiscos from several species of C(4) grasses showed the greatest potential of >50% carbon uptake improvement in wheat, and >25% improvement in sugar beet and maize. This study also reaffirms the need for data on fully characterized Rubiscos from more species, and for better parameterization of ‘V(cmax)’ and temperature response of ‘J(max)’ in ESMs.