Next generation biofuels require higher yields with lower inputs as breeders and engineers develop new generations of biofuel feedstocks. To drive future yield gains we will target carbon assimilation and water acquisition to gain a deeper understanding of the key limitations and potential control points to improve light and water use efficiencies (WUE). The target bioenergy feedstock will be Sorghum bicolor with gene discovery driven by the model system Setaria viridis. Sorghum is an attractive bioenergy feedstock supported by a well-developed breeding and seed industry to meet feedstock demands across the U.S. Recent investments by DOE specifically targeting understanding and improvements of sorghum will be leveraged in this proposal to further accelerate sorghum feedstock improvements. We will use S. viridis as a rapid cycling model together with S. bicolor to test synthetic circuits, develop new gene editing and transformation technologies and conduct GWAS studies to identify genes and novel allelic variation to improve sorghum productivity. These genes and networks will largely be identified through a suite of new computational tools and high resolution and throughput phenotyping capabilities. Recent advances in genome editing and transformation will enable us to rapidly deploy new synthetic circuits into S. viridis to test hypothesis quickly and efficiently. These circuits will then be installed into sorghum. We have assembled a multi-disciplinary team with expertise ranging from plant physiology, genetics, molecular biology, informatics, computational biology and genetic engineering. Six objectives (with lead PIs) have been defined as detailed below.

Obj. 1:Engineer photosynthesis for improve performance under water stress (Baxter, Cousins)
Obj. 2: Optimize water relations to enhance drought tolerance and WUE (Cousins, Dinneny, Leakey)
Obj. 3: Develop a comparative GWAS pipeline for sorghum and Setaria (Baxter, Mockler)
Obj. 4: Use metabolic network modeling to guide biomass engineering (Rhee, Mockler) 
Obj. 5: Manipulate plant gene expression through precision engineering (Voytas, Kausch)
Obj. 6: Develop methods to improve transformation efficiencies in sorghum and establish a regulatory framework for deployment of engineered organisms (Kausch)

A major goal of the proposed work is to identify genes and pathways that contribute to enhanced growth and productivity under drought conditions. These genes will provide targets for plant breeders and genetic engineers to re-design sorghum specifically as a high value bioenergy feedstock to be grown on marginal soils and not compete with food crops. We will also develop new technologies to limit the flow of pollen and reduce the risk of unintended release of transgenic materials into the environment. We will work closely with regulatory agencies to develop best practices for designing engineered organisms and establish a framework for future deployment of transgenic materials to the field. The development of a low input, environmentally safe and highly productive sorghum germplasm will help establish a lignocellulosic energy economy that can provide jobs to rural communities, ensure energy security and benefit the environment.