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 U.S. Department of Energy (DOE) has deemed switchgrass a promising biomass crop to help replace America’s dependence on fossil fuels. Yet the amount of lignin – the cementing agent that holds plant cell walls together – in switchgrass has slowed the process down. ARS scientists hope the snapshots will show them how they can conventionally breed or genetically engineer new varieties of the grass with a diminished capacity to produce lignin.

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.

The goal: to find which genes have been turned on or shut off during such moments, says Sarath, at the ARS Grain, Forage and Bioenergy Research Unit in Lincoln, NE.

Since 2003, Sarath, Paul Twigg of the University of Nebraska-Lincoln and Christian Tobias, a molecular biologist with ARS in Albany, CA, have determined the sequences of about 12,000 switchgrass gene fragments. At least 12 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.

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

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