Demand for food and fuel is steadily increasing and a major challenge in biology is to discover ways to increase crop productivity. One potential route is by improving photosynthesis. The enzyme Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) can catalyze the combination of ribulose-1,5-bisphophate with carbon dioxide, but also can catalyze the reaction of ribulose-1,5-bisphophate with oxygen, a process in which previously fixed carbon dioxide is lost. Cyanobacteria and some land plants have mechanisms that concentrate carbon dioxide near the enzyme Rubisco that prevents it from reacting with oxygen, a process called carbon concentrating mechanism. However, many of the globally important crop plants lack this ability. In this collaborative project investigators from the US (Cornell University) and the UK (Lancaster University and Glasgow University) seek to use newly developed synthetic biology tools to create a carbon concentrating system in a plant that lacks this capability. The project provides interdisciplinary training opportunities, including with their international collaborators, in quantitative and synthetic biology.
One strategy to improve photosynthetic yields is to replace a crop plant's Rubisco with a faster enzyme along with a carbon-concentrating mechanism. The overall goal of this project is to build the cyanobacterial carbon concentrating mechanism in tobacco as a model system. This will be accomplished by designing, building, and testing three component parts: 1) engineering a nuclear-encoded bicarbonate transporter onto the chloroplast envelope; 2) removing the chloroplast carbonic anhydrase; and 3) expressing all of the cyanobacterial carboxysome proteins from the chloroplast genome. Biochemical and microscopic studies will be performed to determine the effect of stoichiometry of cyanobacterial proteins on microcompartment size, morphology, and function in carbon concentration and photosynthesis. Chloroplast transformants will be analyzed to determine the features of the gene regulatory sequences in the synthetic chloroplast operons needed to express proteins in the amounts and ratios needed for assembly of microcompartments.
This collaborative US/UK project is supported by the US National Science Foundation and the UK Biotechnology and Biological Sciences Research Council.
