Web exclusive posted Dec. 21, 2008, at 12:21 p.m. CST 
 
 Indiana-based Purdue University researchers believe they have made a discovery which has potential to serve as a significant development in the production of cellulosic ethanol, as well as numerous other applications. 
 

 Botany and plant pathology professor Nicholas Carpita and his research team learned that small-interfering RNA are a key element in a plant's development of cellulose. Naturally, these mechanisms terminate cellulose production in plants by shutting down genes associated with primary cell wall development to allow for the secondary cell walls to form. They can also activate gene expression, and are known as an antiviral mechanism. 
 
 "If we can learn to interfere with the down-regulation of cellulose synthesis, then plants may be able to produce more cellulose, which is key to biofuels production," Carpita said.
 
 The discovery was made when the research team introduced a virus to a barley plant to silence certain genes in order to study specific functions. After comparing the targeted plant with a control barley plant, the researchers realized the small RNAs were responsible and already in the controls even without adding the virus.
 
 The researchers believe that delaying or preventing the shutdown of both primary and secondary cellulose production in plants might enhance total plant biomass. 
 
 Carpita said his interest in cellulose synthesis has been life long. "I did a post-doctorate with Debby Delmer from 1977 to 1979 at the Michigan State University Department of Energy Plant Research Lab in East Lansing, and that kindled my interest in the plant cell wall and cellulose synthesis," he said. "I came to Purdue in 1979 and have always worked on the structure and synthesis of plant cell walls, particularly those of grasses, which are different from all other flowering plants."
 
 Carpita said about four years ago, post-doctorate Mick Held joined his group and began studies in collaboration with colleague Steve Scofield, to discover if virus-induced gene silencing could be used to knock out various cell wall genes. "Specifically so we could establish their functions," Carpita said.
 
 "Scofield was one of the first to do this in a grass species, so it was of particular interest to knock out grass-specific cell wall-related genes. We soon found out that no matter how specific the target for gene silencing, many other cell wall-related genes were also knocked out," he said. 
 
 When Held began looking at the small RNA products expected from the virus-induced silencing, he found them in the controls as well. "We knew then that this was a natural mechanism of silencing unrelated to the virus-induced silencing," Carpita said. "Cellulose synthase appears to be at least one of the major entry points into the silencing of the broad range of cell wall genes. Thus, interrupting this natural down-regulation is the focus of our current research. We know full well that there is another tier of regulation that controls when the antisense RNAs responsible for the silencing come on, so the next question is the obvious one: what regulates the regulators?"
 
 Although this finding has an obvious impact for the biofuels area, small RNA control of process is widespread and certainly not confined to cellulose synthesis and a whole host of applications could be imagined where control of production of plant metabolites could be of commercial value, according to Carpita.

 
 In the future, the research group intends to keep focused on the biology of the regulation. "We also are involved in DOE supported work to define the genes involved in the synthesis of biomass," he said. "We estimate that plants devote about 10 percent of their genome to synthesis of cell walls—about 2500 genes. We currently have rudimentary knowledge about the function of about one-half of them, with a true established specific function of only a few dozen. We aim to augment that list enormous over the next few years."
 
 Carpita said the Purdue researchers are strong proponents for the use of maize as the prime genetic vehicle for gene discovery that, by virtue of the close evolutionary relationship to the more highly touted energy grasses, makes translation to these species. "We and many others think it is way too early to write off maize as an energy crop itself," he said. 
 
 The connection with food versus fuel with grain is truly unfortunate, Carpita added. "It is generally agreed that the energy return is very small, but maize has a broad range of genetic diversity that has not yet been exploited for its potential as a dedicated energy crop."
 
 Carpita pointed out that tropical maize grows up to 20 feet, with very thick stems that are loaded with sugar. "They could become the sugarcane of the Midwest," he said. "Not without some trade-offs, but certainly better than grain by about five-fold, and a much more favorable appeal as an annual crop that can be accommodated in a three-year rotation with grain corn and soybeans. " 
 
 The research report that, which was published Dec. 15, is available online on the Proceedings of the National Academy of Sciences Web site, <a href="http://www.pnas.org/content/early/2008/12/15/0809408105.full.pdf+html">http://www.pnas.org/content/early/2008/12/15/0809408105.full.pdf+html</a>.

Purdue researchers make cellulose discovery

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Purdue researchers make cellulose discovery