Professor Don Ort, Departments of Crop Sciences and of Plant Biology, University of Illinois, USA.
Lowering the Costs of Photorespiration
Photorespiration is essential for C3 plants in the earth’s oxygen containing atmosphere but operates at a massive expense of fixed carbon dioxide and energy. Photorespiration is initiated when the initial enzyme of photosynthesis, ribulose-1,5-bisphosphate carboxylase/ oxygenase (Rubisco), reacts with oxygen instead of carbon dioxide and produces the toxic compound glycolate that is then recycled by photorespiration. Photorespiration can be modeled at the canopy and regional scales to determine its cost under current and future atmospheres. A regional-scale model reveals that photorespiration currently decreases US soybean yields by 36% while consuming 40% of plant’s ATP and 30% of the plant’s NADPH production during peak canopy photosynthesis. Reducing photorespiratory yield losses by 5% (i.e., to 31% for soybean would be worth ~$500 million annually in the United States). Furthermore, photorespiration will continue to impact yield under future climates despite increases in carbon dioxide, with models suggesting a 12–55% improvement in gross photosynthesis in the absence of photorespiration, even under climate change scenarios predicting the largest increases in atmospheric carbon dioxide concentration. Although photorespiration is tied to other important metabolic functions, the benefit of improving its efficiency appears to outweigh any potential secondary disadvantages. Synthetic biology has provided new opportunities in altering photorespiratory metabolism to improve photosynthetic efficiency. Indeed metabolic bypasses to photorespiration have been generated and have demonstrated improvements in growth. Using a synthetic biology approach we have assembled a series of multigene constructs that contain alternate metabolic pathways to bypass the native photorespiratory pathway while preventing glycolate flux into the native pathway. Greenhouse studies of the best performing events of T1 homozygous single insert plants of these photorespiratory bypasses in tobacco showed >20% biomass increases, which were confirmed and extended by replicated field trails during the 2016 & 2017 growing season.
Don Ort is the Robert Emerson Professor of Plant Biology at the University of Illinois, Director of the USDA-ARS Photosynthesis Research Unit and Deputy Director of the $45M multi-national Bill & Melinda Gates Foundation RIPE Project. He is a member of the National Academy of Sciences and listed in 2016 at one of the Most Highly Cited Authors in Plant and Animal Biology.