Comparative proteomic analysis of sweet and grain sorghum stem internodes: mechanisms of sugar accumulation for bioenergy
EMSL Project ID
47960
Abstract
The amount of biomass produced by plants and its composition is largely dependent on fixation of atmospheric CO2 as sugars through photosynthesis by plants. Among the several potential bioenergy feedstocks, sorghum stands out due its low nutrient and water requirements, and high biomass production, but most importantly due to the ability of some genotypes to accumulate fermentable sugars in the stem internodes. Although traditionally grown as a grain crop, the availability of genotypes that accumulate sugar in the stems makes it an excellent system to study sugar partitioning in a bioenergy grass. Use of sugar hyper-accumulating or “sweet” sorghum as feedstock for ethanol production requires costly processing before fermentation and hence can eliminate the biggest economic barrier to biofuel deployment. The exact mechanism of sugar accumulation is not very well defined. Related work in sugarcane and corn suggest a role of sugar transporters in this process. Available evidence is conflicting regarding the role of sugar metabolizing enzymes and sugar interconversions in sugar hyper-accumulation. Overall, the physiological processes and underlying genes responsible for sugar accumulation are largely unknown. We propose proteomic profiling of sorghum stem internodes to identify the key proteins involved in sugar accumulation. We will use differences in tissue localization and between select sorghum genotypes that differ in their ability to accumulate sugar in the stem internodes. We will then characterize these candidates by performing a more targeted proteomics for selected protein candidates identified in the initial proteomic screen. The precise in vivo role of these candidates will then be established in follow up experiments analyzing gene expression, biochemical, radiometabolite, and whole-plant carbon allocation assays using radiotracer imaging in mutant and transgenic plants. This project is an off-shoot of a collaborative project between BNL, the University of Missouri, and the University of Nebraska funded by the USDA-DOE Feedstock Program to identify the mechanisms responsible for sugar accumulation in sweet sorghum stems (Title: Functional genomics of sugar content in sweet sorghum stems; FOA No: DE-FOA-0000417). The sweet and grain sorghum model is perfectly suited to study critical aspects of basic plant biology including phloem unloading, and carbohydrate partitioning, between competing sinks in a bioenergy crop. Our efforts will be complemented by the availability of a QTL population segregating for sugar content as well mutant TILLING lines in sorghum that will be generated by our collaborators. Successful completion of this work will help us not only to identify the potential candidate proteins associated with high sugar accumulation in the stems of sorghum but this information can also be very useful to improve the composition of other bioenergy grass feedstocks.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2013-10-01
End Date
2015-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members