A synthetic biology approach to crop improvement: Bottom-up construction of a proteinaceous Rubisco organelle

A long-term strategy to enhance global crop photosynthesis and yield involves the introduction of micro-algal and cyanobacterial CO₂-concentrating mechanisms (CCMs) into C₃ plant chloroplasts. The CCM of cyanobacteria enables relatively efficient CO₂ fixation by elevating intracellular inorganic carbon as bicarbonate using specialised bicarbonate pumps on the inner membrane, then concentrating it as CO₂ around Rubisco in a specialized protein micro-compartment called a carboxysome. Such a mechanism, once grafted into C₃ plants, theoretically enables high rates of CO₂ fixation at lower nitrogen and water cost. The carboxysomes operate as prokaryotic organelles, isolating Rubisco to a high CO₂ environment within the cell. Within the engineering approach to build a chloroplastic CCM, the construction of functional carboxysomes in the chloroplast is a complex task. I will describe the proposed biogenesis and function of α-carboxysomes from cyanobacteria and our bottom-up approach to building these structures in C₃ plants.

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