Functional Genomics of Sugar Content in Sweet Sorghum

Sweet sorghum [Sorghum bicolor (L.) Moench] represents an ideal crop for the production of bio-ethanol. It has a sugar-rich stalk and produces high biomass with low input. In addition, it is widely adaptable, requires minimal fertilization, and because it is a drought tolerant C4 crop, it has high water-use efficiency and can be planted in non-arable and marginal lands. Moreover, it has a diploid genome that has been sequenced making it a good model system for more complex genomes, such as the polyploid sugarcane. Compared to grain sorghum, sweet sorghum is taller, has a smaller panicle, produces lower grain yield, and more importantly, it accumulates significantly higher sugar concentrations in the stem, which suggests that there are differences in carbon flux between the two lines. Thus, comparing grain and sweet sorghum will lead to a better understanding of the regulation of carbon partitioning within plants. This research project is aimed at understanding the mechanisms that regulate carbon transport and allocation to the stem of sweet sorghum. Our specific goals are to: 1) measure bioenergy-relevant traits such as plant height, dry matter, sugar levels and gas exchange related parameters; 2) characterize the expression and function of sucrose transporters (SUTs) in different sorghum tissues; and 3) determine the structural and functional differences of the transport system between sweet and grain sorghum. Results from this research could lead to the improvement of sucrose accumulation in the stem of sweet sorghum.