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Crop Biotech Update

Mutated Corn Gene Expressed in Switchgrass Improves Digestibility and Starch Content

October 14, 2011

(complete access to journal article may require payment or subscription)
http://www.pnas.org/content/early/2011/10/04/1113971108.abstract?sid=d94a0389-4be0-4059-a434-508a5616707e
http://biofuelsdigest.com/bdigest/2011/10/12/mutaged-corn-gene-triples-starch-content-in-switchgrass-researchers

Researchers from the Plant Gene Expression Center of the United States Department of Agriculture (USDA) and University of California (UC) Berkeley improved the digestibility, and increased the starch content of switchgrass (Panicum virgatum L). The resulting "tailored switchgrass" is reportedly one that is a better bioenergy crop for biofuel-ethanol production. Their strategy is based on the observation that plants in the "juvenile phase" are "less lignified" and displays differences in biomass accumulation/character that point to less biomass recalcitrance (tendency of biomass to resist pretreatment and processing to ethanol, due to the high lignin content). 

They studied and harnessed the genes that regulated the transition of plants from juvenile to adult phase, to make tailored, dedicated bioenergy switchgrass. What they did was to express a key gene from corn (Corngene1 or Cg1 gene) into switchgrass. The mutant Cg1 gene, according to the study, "fixes plant development in the juvenile phase". In corn, these mutant genes produce biomass with reduced adult characteristics, and the leaves have less lignin and higher sugar levels compared to the wild type. When the mutant Cg1 gene was expressed in switchgrass, the plants were "found to have up to 250% more starch, resulting in higher glucose release from saccharification assays with or without biomass pretreatment". Furthermore, the modified switchgrass did not show evidence of flowering during the two-year trial period, indicating that the "transfer of genetic modification was low". These results show the potential for lowering the production cost of cellulose-ethanol by reducing pretreatment inputs. The full study is published in the Proceedings of the National Academy of Sciences (URL above).