Mechanism of Carbon Partitioning Regulation by cpg13 in the Bioenergy Woody Crop Poplar

2009 Awardee

Investigators: M. Kirst and G.F. Peter

Institution: University of Florida

Non-Technical Summary: Plant biomass is composed primarily of cellulose, lignin, and hemicellulose. The lignin content of biomass limits bioconversion of wood cellulosics to renewable biofuels by decreasing the available amount of carbohydrate and by hindering cellulose degradation. High lignin content also negatively impacts biomass productivity in several woody species. Therefore, characterizing genes that regulate the balance of carbon going to cellulosics or lignin can lead to the development of plant materials that are more suitable for biofuel production. We have recently identified a previously uncharacterized gene, cpg13(carbon partitioning and growth in chromosome 13), as a key regulator of carbon partitioning to lignin and cellulose and of biomass productivity in Populus.

Objectives: We hypothesize that cpg13 regulates the metabolic competition for carbon, affecting growth, cellulose biosynthesis, and lignification. In this project we will identify the molecular role of cpg13 by (1) characterizing its function in the regulation of gene expression, metabolites, and cell wall chemistry and structure and by (2) determining its spatial and temporal expression and subcellular localization.

Approach: In the first objective, changes in transcriptome, metabolome, and wood chemistry and structure associated with altered cpg13 expression in homogeneous, pure genetic backgrounds of both P. deltoides and P. trichocarpa will be characterized. To dissect the quantitative contribution of cpg13 to changes in phenotype, we will utilize transgenic plants over- and under-expressing the gene in each of the two species.

In the second objective, two complementary approaches will be used to determine which cell types express cpg13 and its subcellular localization in poplar. In the first approach, green fluorescent protein (GFP) will be fused in frame at its carboxy terminus to the native gene, and this construct will be transformed into poplar. These transgenic plants will be used to analyze expression in different organs, cell types, and ontogenetic stages. In the second approach, antibodies that specifically recognize cpg13 will be developed to confirm protein abundance, subcellular localization by transmission electron microscopy, and biochemical fractionation studies.

Project Contact
Name: M. Kirst
Phone: 352-846-0900
Fax: 352-846-1277
Email: mkirst@ufl.edu