This action funds an NSF National Plant Genome Initiative Postdoctoral Research Fellowship in Biology for FY 2019. The fellowship supports a research and training plan in a host laboratory for the Fellow who also presents a plan to broaden participation in biology. The title of the research and training plan for this fellowship to Sarah Stainbrook is "Improving C4 Crop Tolerance for Heat Stress by Engineering Thermostable Rubisco Activase". The host institution for the fellowship is the Donald Danforth Plant Science Center (DDPSC) and the sponsoring scientist is Dr. Ru Zhang.
Global population growth, coupled with a transition to dependence on biofuels, will require a doubling of production of maize and other grain crops by 2050. However, the projected 3.5 degrees Celsius temperature increase in 2050 will reduce global maize production by 23%. Even now, heat waves such as those experienced by the U.S. in 1980, 1988 and 2012 could devastate agricultural productivity, with losses estimated at 55, 71, and 31 billion dollars, respectively. One solution to this impending food security crisis is by improving the thermotolerance of crops to withstand heat stress by focusing on Rubisco activase (Rca), the most thermosensitive enzyme involved in photosynthesis. This project will leverage naturally occurring variation in Rca in different plants to find or create a Rca enzyme variant that can improve the ability of maize to withstand high temperatures. Broader impacts include teaching a non-majors undergraduate biology class to improve science literacy and mentoring high school students from underprivileged or minority backgrounds through the Mutant Millets outreach program at the DDPSC.
C3, C4, and CAM are three different photosynthetic processes that plants use to fix carbon. One of the primary factors limiting carbon fixation during heat stress is the activation state of the carbon fixation enzyme Rubisco. Rubisco must be activated by its catalytic chaperone, Rubisco activase (Rca). It is estimated that the net photosynthesis rate of maize could be doubled at 40 degrees Celsius if a thermostable Rca could be found or created. This research will focus on identifying and isolating variant Rca enzymes from C4 crops maize and sorghum, as well as the closely related model grass, Setaria viridis. Rca isolates from these plants will be characterized by in vitro carbon assimilation assays and correlated to chlorophyll fluorescence and gas exchange measurements taken from intact plants. Heat-adapted isolates from these plants, as well as from C3, C4 and CAM plants from a variety of environments, will be similarly assayed to determine the range of naturally occurring variation in Rca thermotolerance. Additionally, protein engineering techniques will be used to improve Rca thermostability. Variants with improved properties will be introduced into S viridis to verify that the engineered thermostable enzyme improves thermotolerance of photosynthesis in the transgenic plant. Once verified, the engineered thermostable Rca will be introduced into maize. All phenotypic and biochemical data generated in this project, including from plants from diverse climates, will be added to existing genetic information maintained in a publicly accessible database and further disseminated through peer-reviewed publications and conference presentations.
Keywords: thermotolerance, carbon fixation, maize, C4 photosynthesis, Rubisco activase.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
