Evolving Methanococcoides burtonii archaeal Rubisco for improved photosynthesis and plant growth

Improving the performance of the CO2-fixing enzyme Rubisco has the potential to significantly enhance photosynthetic efficiency and yield1. Strategies to achieve this goal involve either modifying the biochemistry and ultrastructure of leaf chloroplasts to concentrate CO2 around Rubisco, or directly improving Rubisco catalysis itself by genetic crossing or transgenic modification2. While both approaches face significant technical challenges, suggestions that Rubisco in plants is already operating at or near physiological optimum poses uncertainty as to the level of improvement possible3,4. Somewhat overlooked in these small data set analyses is that plant Rubisco is not the pinnacle of evolution - as the superior Rubisco from some red algae have the potential to benefit C3-plant productivity by as much as 30%2. Unfortunately, replacing plant Rubisco with red algal Rubisco appears untenable due to chaperone incompatibilities that preclude assembly of algal Rubisco large (L-) and small (S-) subunits into functional L8S8 hexadecamer complexes in leaf chloroplasts5. In recent years there have been significant advances in understanding the complex and specialised ancillary chaperones for the biogenesis of cyanobacteria and plant L8S8 Rubisco6,7,8,9, however homologs for many of these chaperones in red algae are not readily identifiable