Translational Genomics for the Improvement of Switchgrass
Investigators: N.C. Carpita and M.C. McCann
Institution: Purdue University
Non-Technical Summary: In the production of biofuels from lignocellulosic biomass, glucose, xylose and other sugars are released from plant cell walls by hydrolytic enzymes. Dramatic improvements in the rates and final yields of sugar release (saccharification potential) are required, as complex patterns of polysaccharide modification and cross-linking interfere with the ability of the hydrolytic enzymes to release sugars, and some modifications result in products inhibitory to fermentative bacteria. Non-cellulosic polysaccharides of grass walls are potentially abundant sources of glucose and xylose if the structures are made more accessible by genetic manipulation. Switchgrass is targeted to become a future biomass crop, but the discovery of genes underlying biomass-relevant traits is compromised in switchgrass by the paucity of genetic resources. Maize provides a genetic resource for improvement of distinct cell walls of switchgrass and other energy grasses.
Objectives: Bioinformatics and high throughput sequencing technologies will be used to identify and classify the genes involved in cell wall formation in maize and switchgrass. Targets for genetic modification will be identified and tested for enhanced processing ability.
Approach: A description of function for an estimated 1500 genes related to cell wall biology will be provided for switchgrass, based on homology to maize and rice sequences, and augmented with gene families that are currently of unknown function but are implicated in cell wall development. Maize cell wall gene family members that are highly expressed during primary and secondary wall formation will be determined, and regulatory small RNA sequences will be identified. These data will be the foundation for identification of switchgrass orthologs. As proof of concept, we will test mutants and transgenic lines of maize for release of glucose and xylose in functional analyses of genes that impact structure and degradability of non-cellulosic polysaccharides. We will also test the function of a gene family of unknown function that is known to impact cellulose content. Analyses of cell wall structures and saccharification potential will be applied to developing stems and stover of maize and switchgrass, to our collection of cell wall-related mutants available at project start, and to lines with modulated expression of our genes of interest.
Name: N.C. Carpita