An increasing global population, shifts in land use, economic development, global climate change, and rising energy prices have put a strain on the current food production system. These challenges have resulted in major food price swings and uncertainties surrounding global food security. As rice and wheat yields have plateaued in recent years, new and innovative ways of increasing yield and improving water and nutrient use efficiency need to be actualized.
To sustainably produce food and feedstocks to meet the rising demand, crops need to be both higher yielding and more efficient. C3 crops such as rice and wheat are inefficient under hot and dry conditions. Through a series of adaptations, C4photosynthesis has evolved as a more efficient method of carbon fixation than C3photosynthesis. The engineering of C4 photosynthesis traits into less productive C3crops is one approach to solving global food and bioenergy issues. To accomplish such goals, it will be necessary to achieve a better understanding of the biology that drives C4 photosynthesis. In addition, a better understanding of C4 photosynthesis would inform breeders and synthetic biologists of possible ways of improving C4 crops.The challenge is not food vs. fuel, it is food and fuel.
As a postdoc in Dr. Tom Brutnell’s lab: Enterprise Rent-A-Car Institute for Renewable Fuels at the Danforth Center, my work is focused on the initial steps of C4 photosynthesis and the evolution of the carbon concentrating mechanism (CCM) in monocots. The advantages of C4 photosynthesis can be attributed to the leaf anatomy and biochemistry that form the CCM. Unlike C3 photosynthesis, where all of the biochemical reactions take place in a single cell, C4 photosynthesis is commonly achieved with a modified cellular arrangement known as Kranz anatomy, which divides the reactions into two cell types. This modified leaf anatomy allows the CCM of C4 photosynthesis to greatly increase CO2 around Rubisco in the chloroplasts of bundle sheath cells, which effectively eliminates photorespiration and consequentially improves both water and nitrogen use efficiency. In other words, C4plants use less water and less nitrogen to attain higher yields than their C3 cousins.
Despite the well-researched biochemical role of the enzymes involved in the CCM of C4 photosynthesis, little is known about the genetic regulation and cellular biology of these fundamental enzymes in C4 monocots, and how these relate to photosynthetic efficiency. New transformation protocols, powerful molecular tools, and high-throughput sequencing technology allow us to investigate the central enzymes involved in C4photosynthesis in monocots. This research has both basic and applied aspects, and addresses questions about the enzymes involved in photosynthesis that have gone unanswered for more than 50 years.
To aid in our research efforts, we recently hired Allison Kolbe as technician in the lab. Allison was an National Science Foundation Research Experiences for Undergraduates intern in the Brutnell Lab during the summer of 2012 and worked on a project in Setaria viridis to characterize carbonic anhydrase. Carbonic anhydrase catalyzes the first dedicated step in C4photosynthesis. Her work complimented the characterization of carbonic anhydrase in maize. After graduating in December of 2012 from Ohio Wesleyan University with a double major in Botany and Spanish (and a double minor in chemistry and music), Allison moved to St. Louis in January and will be working in the lab until she starts graduate school in the fall of 2013.
With Allison’s help we have been able to take a comparative approach to understanding the CCM. By looking at both C4 and C3 plants we can dissect the evolutionary changes lead to the CCM. We are studying crops such as maize (C4), sorghum (C4), and rice (C3), as well as the model plants Setaria (C4) and Brachypodium (C3). We have also started to study Dichanthelium oligosanthes, a C3grass that shares a common ancestor with maize and Setaria. Dichanthelium may be an intermediate between C3 and C4 photosynthesis, which would provide unique insight into the evolution of C4 photosynthesis in monocots. Because Dichanthelium is a perennial, with the help of greenhouse staff, we recently moved it outside onto the Danforth Center patio to induce dormancy for the winter. So when it looks like we are transplanting weeds, it just goes to show how committed the Danforth Center is to novel research approaches.
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