INVESTIGATORS: Braun, D. M., Dweikat, I., Ferrieri, R., Babst, B.
INSTITUTIONS: University of Missouri-Columbia, University of Nebraska-Lincoln, Brookhaven National Laboratory
NON-TECHNICAL SUMMARY: Enhancing the production and conversion of plant feedstocks to utilizable sources of energy will decrease the U.S. dependency on fossil fuels while reducing greenhouse gas emissions. Sweet sorghum is a rapidly growing, high biomass, widely adaptable crop with tremendous potential for biofuel production. Sweet sorghum accumulates very high concentrations of sucrose in the stem, which can be efficiently converted to ethanol. We hypothesize that sucrose accumulation in sweet sorghum can be further improved if we understand the mechanisms regulating carbon allocation to stems. The proposed research will use a combination of approaches, spanning genomics, molecular genetics, biochemical phenotyping, and detailed physiological studies to identify bioenergy-relevant genes and to understand their functions in carbon partitioning in sweet sorghum. The knowledge obtained through this project will provide valuable information toward improving sweet sorghum for bioenergy.
OBJECTIVES: 1. To map and clone Quantitative Trait Loci (QTLs) related to stem biomass, total biomass, and sugar accumulation in sweet sorghum stems. 2. In order for sucrose to accumulate to high levels within sorghum stem internodes, it must be transported across the plasma membrane, presumably by sucrose transporters (SUTs). We will characterize all SUTs in sweet sorghum to determine their functions. 3. To understand the partitioning of carbohydrates to stem tissue, we will perform comparative phenotyping of the plant materials relevant to aims 1 and 2, using a robust and highly sensitive radiochemical tracer, carbon-11 (11C).
APPROACH: This project will screen a set of recombinant inbred lines (RILs) that were developed from a cross between a sweet and grain sorghum that differ in a number of traits, including total soluble sugar in the stalks, as well as grain and total biomass production. The data generated from this aspect of the project will be useful for the identification of markers linked to genes that control QTLs of economic importance in sweet sorghum. In parallel, quantitative RT-PCR will be used to measure the expression level of all sorghum SUT genes in multiple tissues. RNA in situ hybridization will be used to determine which genes are specifically expressed in stem phloem vs. storage parenchyma cells. Reverse genetic approaches will be used to determine the functions of select SUTs and to identify which ones have critical roles in the stem accumulation of sucrose. Additionally, we will use the short-lived radiotracer 11C, administered as 11CO2 to leaves, for phenotyping whole-plant carbon transport dynamics. Concurrently, some destructive harvesting will be conducted to measure biochemical partitioning of 11C to sugars, starch, and cellulose in the source leaves, internodes, and panicles, and to correlate gene function data from objectives 1 and 2 with 11C transport and partitioning characteristics.
Name: Braun, D. M.