Improving carbon fixation

The Calvin–Benson (CB) cycle fixes carbon dioxide from the atmosphere into carbon compounds that are then used to make an array of molecules essential for plant growth and development. The efficiency of this cycle is known to be lower than its potential maximum and the goal of improving it has been an objective of plant scientist over the last 20 years. A major limitation to the CB cycle is the first enzyme in the cycle, ribulose 1,5-bisphosphatase, but evidence has also accumulated identifying additional enzymes sedoheptulose 1,7-bisphosphatase and fructose 1,5 bisphosphate aldolase, which share some of this limitation. In this chapter, we review the progress of the work to achieve improvements in CO2 assimilation through improving the function of CB cycle by the (1) engineering of rubisco, (2) introduction of novel pathways or mechanisms to improve the function of rubisco, and (3) direct manipulation of the levels of activity of CB cycle enzymes. Examples are given of successes obtained using these approaches and the limitations of the current approaches and the future prospects are discussed in the context of rising CO2 levels.