Towards the Development of Sustainable Feedstocks for Renewable Biobased Products: The Case for Sugarcane and Sweet Sorghum

Sugarcane (Saccharum officinarum) and sweet varieties of sorghum (Sorghum bicolor) can produce over 60 ton ha^-1 fresh biomass, with accumulation of sugar reserves in their respective stalks of 15% or greater. These biomass yield attributes, coupled with their capacity to perform C4 photosynthesis and relatively low agronomic input requirements make sugarcane and sweet sorghum ideal biomass feedstock targets for renewable biobased products. We have assembled a research team with a diversified skill-base to allow us to take a holistic approach to address selected input and output traits to improve the attractiveness of these commodities as biomass feedstocks for biobased products.  To this end, we are focusing our efforts on avenues to improve one input trait, photosynthetic capacity, under both optimal and cold stress, and the output trait of shifting metabolic flux in the parenchyma cells of stalks to alter the carbon reserves from sucrose to lipids within the cells.  To address these target traits we are translating strategies developed from studies conducted with model organisms in a systematic fashion by evaluating modification of these approaches in single and combinatorial gene stacks and subsequently phenotyping transgenic events of sugarcane and sorghum.  The information gathered from the phenotypic analyses of these first generation of transgenic events are forming the basis of synthetic genetic designs that carry multigene stacks which simultaneously target both the input trait, photosynthetic capacity and the output trait, carbon flux changes in parenchyma cells of stalks as a means to accumulate lipid reserves.