Chemistry Proposal Defense Seminar – Jacob Lewis

About the event

Title:
The Intersection of Biofuel and Crop Resilience: Enzymatic Characterization for Future Engineering

Abstract:
Fuel crops such as Sorghum bicolor and Panicum virgatum have been identified by The United States as Strategic Plants for rational bioengineering of the next generation of fuel crops. Under the Energy Independence Security Act of 2007, the U.S. established a national goal of replacing 30% of petroleum-based fuels with lignocellulosic fuels by the year 2030. The main barrier hindering access to cellulose is the polymer lignin. Recently it was discovered that lignin contains more than the three originally identified monomers from the monolignol pathway. It also includes tricin, a flavonoid in a neighboring branched enzymatic pathway. The intertwined nature between the pathways presents an opportunity to investigate and rationally design engineered plants that reduce lignin content while increasing biomass through the flavanone/flavonoid pathway. Flavonoid research has expanded drastically in recent years with benefits to cancer, antibacterial, and antiaging research. The enzyme at the branching point, Chalcone Synthase (ChS), diverts biomass away from the monolignol pathway towards flavonoid/flavanol molecules. Crystal structures have been obtained of ChS detailing the mechanism of binding the large CoA derivative substrates. The three following enzymatic reactions are Chalcone Isomerase (ChI), Flavanone 3-Hydroxylase (F3H), and Dihydroflavonol 4-Reductase (DfR). F3H and DfR are the critical enzymes for synthesis of metabolites involved in plant coloration and defense mechanisms but are poorly understood while ChI preforms a Michael Addition that is stereospecific. DfR crystals allowed for binding site characterization of NADPH and the hydride acceptor flavanol. The results of this work will provide detailed characterization of the pathway, necessary for future development of bioengineered plants to produce reduced lignin for ease of access to cellulose and other valorization.