Scientists Turn Genetic Keys to Unlock Bioenergy in Switchgrass

Using genetic "snapshots" of switchgrass, Agricultural Research Service (ARS) and collaborating scientists are gaining new insight into how this warm-season perennial plant could be harnessed as an ethanol resource.

The snapshots are actually fragments of genetic material called messenger RNA (mRNA), and they're like molecular workhorses that do the bidding of DNA (deoxyribonucleic acid). One key task is delivering instructions to make proteins.

Over the past few years, ARS molecular biologist Gautam Sarath and colleagues have generated tens of thousands of the mRNA snapshots depicting switchgrass from the moment it sprouts from seed to the time it girds itself for winter.

Determining the nucleotide sequences of the mRNA snapshots provides clues as to which genes have been turned on or shut off during such moments, according to Sarath, at the ARS Grain, Forage and Bioenergy Research Unit in Lincoln, Neb.

Since 2003, Sarath, Paul Twigg of the University of Nebraska-Lincoln and Christian Tobias, a molecular biologist with ARS in Albany, Calif., have determined the sequences of about 12,000 switchgrass gene fragments. At least 12 of them are associated with genes that regulate the production and deposition of lignin, the cementing agent that holds plant cell walls together.

Bioenergy producers are keen on loosening the grip of lignin so that more of the sugars locked within the cells of switchgrass can be fermented into ethanol. Currently, sugars from the starch of grain crops like corn are used. One possible approach is to conventionally breed or genetically engineer new varieties of the grass with a diminished capacity to produce lignin.

To speed the discovery of important genes besides those for lignin production, the ARS scientists submit the genetic fragments they amass to the U.S. Department of Energy's Joint Genome Institute in Walnut Creek, Calif. There, scientists employ state-of-the-art sequencers so that the fragments' identities and function can be more quickly determined through comparisons to the genomes of corn, rice and other grasses.

Read more about this and other ARS bioenergy research in the April 2007 issue of Agricultural Research magazine.

ARS is the U.S. Department of Agriculture's chief scientific research agency.