Improving Photosynthesis to Increase Crop Yields
Demand for food and fuel is steadily increasing, while gains in the yield of many major food crops through traditional breeding and natural variation have leveled. As a potential solution, researchers are applying synthetic biology to improve photosynthesis. Maureen R. Hanson, Molecular Biology and Genetics, is focusing on an enzyme that limits the efficiency of photosynthesis—rubisco. Instead of converting carbon dioxide into energy, rubisco can sometimes catalyze a reaction with oxygen. This leads to photorespiration, a process in which previously converted or fixed carbon is lost.
Cyanobacteria and some land plants have mechanisms that concentrate carbon dioxide near rubisco to prevent photorespiration, but many of the globally important crop plants lack this ability. Consequently, these plants must devote considerable amounts of protein to allow rubisco to carry out carbon fixation, which reduces yield and biomass production. One strategy to improve photosynthetic yields is to replace a crop plant’s rubisco with a faster enzyme along with a carbon-concentrating mechanism.
Hanson and her lab are producing vectors that will install a novel cyanobacterial-based, carbon-concentrating mechanism into a chloroplast, and they are providing the necessary molecular machinery to facilitate its operation. To learn how to perform the complex engineering required, work is being carried out in tobacco, a species in which chloroplast transformants can be rapidly obtained. Biochemical and microscopic studies along with analyses of the chloroplast transformants will be performed to assess the effects. Hanson hopes that this technology can be applied to crop plants such as soybean.