Identifying Genes Controlling Feruloylation in Grass Cell Walls
Updated December 2008
Investigators: M.M. de O. Buanafina and D.M. Brown
Institution: Pennsylvania State University
Non-Technical Summary: Ferulic acid residues attached to arabinoxylans, a major component of cell wall of grasses, have the ability to form ferulate dimers functioning in cell wall cross-linking. They are also proposed to act as nucleation sites for the formation of lignin and for the linkage of lignin to the xylan/cellulose network. Such coupling reactions, which occur predominantly in grasses, significantly decrease cell wall degradability and thus work as a barrier against efficient utilization of cell walls as a source of biomass for bioenergy production. We have shown previously that the expression of ferulic acid esterase (FAEA) in different grass species resulted in a substantial reduction in cell-wall-esterified ferulates and diferulates. FAEA expression was shown to impact cell wall hydrolysis, resulting in increased yield of reducing sugars by cellulase treatment as well as increased digestibility. These results reinforce the importance of feruloylation and cross-linking for cell wall degradability.
Objectives: The focus of this proposal is to identify and characterize new genes controlling feruloylation in grasses, as well as new genes that are responsible for the assembly of lignin into the cell wall and for biomass conversion. This will provide fundamental knowledge concerning the most crucial factors that influence grass cell wall degradability.
Approach: Obj. 1. We will generate a highly mutagenized population of Brachypodium with EMS in order to introduce new genetic variation into our model grass Brachypodium distachyona to be used as a resource for identification of the genes involved in feruloylation.
Obj.2. Using two high-throughput spectroscopy–based screening assays we will screen for mutants with altered cell-wall esterified ferulic acid and for improvement in cell wall degradability.
Obj.3 We will characterize a number of these mutants in detail for cell wall properties (e.g., ferulates, sugar composition, lignin content and patterning, degradability, and mechanical properties) and basic genetics (confirm heritability, complementation analysis).
Obj.4 We will identify and isolate the most important of these genes. We will use a mapping population and bulked segregant analysis, identify markers that are genetically linked to a mutation. This will be followed by combination of position cloning and sequencing candidate genes will be used.
The identification of these genes in Brachypodium will serve as a handle for gene discovery in important biofuel crops, such as switchgrass. Thus our efforts will make valuable contributions towards breeding superior cellulosic biomass for biofuels.
Name: M.M. de O. Buanafina
Phone: (814) 867-0223