Metabolic Engineering of Sugarcane for Production of Oil and Increased Biomass Yield

Sugarcane (Saccharum sp. hybrids) has a C4-type metabolism for fixation of carbon and is among the highest biomass producers in tropical and subtropical regions. Sugarcane is a highly efficient crop for ethanol or table sugar production due to the accumulation of sucrose in the stem internodes.

We are exploring the prospects of directing the carbon flux to triacylglycerol (TAG) for increased energy density and development of an advanced biofuel. This strategy involves the analysis of combinations of gene expression cassettes for metabolic engineering, supporting biosynthesis and storage of TAG. Individual or multiple, unlinked candidate gene constructs were co-bombarded into sugarcane callus with the selectable nptII gene. Transgenic sugarcane lines were regenerated on geneticin containing culture media and transferred to soil. Replicated TAG analysis from transgenic sugarcane plants growing under greenhouse conditions and qRT-PCR analysis of individual target genes will be presented. These data indicate the feasibility of genetically engineering the high biomass crop sugarcane to produce TAG. TAG is the most similar chemical to fossil oil and can be readily converted to biodiesel transportation fuel.

Improving light distribution within the sugarcane canopy will likely elevate biomass yield. Lower sugarcane leaves are typically light starved. Therefore, we also explored RNAi suppression of candidate genes which may enhance light transmission into the canopy.  Field performance of transgenic sugarcane with reduced chlorophyll content or altered chloroplast size will be presented.

The work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000206