Bioenergy Advanced by New Tool

A new tool developed by researchers from the US Department of Energy (DOE)'s Joint BioEnergy Institute (JBEI) can help advance the genetic engineering of "fuel" crops for clean, green and renewable bioenergy, according to a new study.

The tool is an assay - an investigative procedure - that allows scientists to identify and characterize the function of nucleotide sugar transporters, which are critical components in the biosynthesis of plant cell walls.

"Our unique assay enabled us to analyze nucleotide sugar transporter activities in Arabidopsis and characterize a family of six nucleotide sugar transporters that has never before been described," Henrik Scheller, a corresponding author in the research, said in a news release. "Our method should enable rapid progress to be made in determining the functional role of nucleotide sugar transporters in plants and other organisms, which is very important for the metabolic engineering of cell walls."

The sugars in plant biomass are an important potential source of energy that can be converted into the transportation fuels gasoline, diesel and jet fuel. In order to gain access to this untapped energy, scientists had to figure out a way to engineer fuel crops whose cells walls have been optimized for sugar content.

Scheller, along with lead authors Berit Ebert, Carsten Rautengarten, developed an assay for characterizing the functions of nucleotide sugar transporters in plant cell walls.

In order to understand how their assay has advanced the bioenergy field, it's necessary to understand sugar transport in a cell.

Most polysaccharide sugars are synthesized in the Golgi apparatus in a cell. But before this step, first these polysaccharides are assembled from substrates of simple nucleotide sugars which are transported into the Golgi apparatus from the cytosol - the gel-like liquid that fills a plant cell's cytoplasm.

For their assay, researchers created several artificial substrates for nucleotide sugar transporters, then reconstituted the transporters into liposomes for analysis with mass spectrometry. This technique enabled them to characterize the functions of the six new nucleotide sugar transporters they identified in Arabidopsis, a relative of mustard that serves as a model plant for research in advanced biofuels.

In addition to these six nucleotide sugar transporters, the assay was used to characterize the functions of 20 other transporters, the details of which will soon be published.

"Thanks largely to the efforts these past two years of Carsten Rautengarten and Berit Ebert, we now know the activity of three times more nucleotide sugar transporters than are known in humans, and we have determined the function of two-thirds of the plant transporters as compared to one-quarter of the human ones," Scheller said. "This is a tremendous accomplishment and we are already using this information at JBEI to improve biomass sugar composition for biofuel production."

Their findings were published in the journal Proceedings of the National Academy of Sciences.