January 15, 2009 (Vol. 29, No. 2)

Scientists at Purdue University say they discovered a mechanism that naturally shuts down cellulose production in plants. Learning how to keep that switch turned on may be the key to enhancing biomass production for plant-based biofuels, notes Nicholas Carpita, Ph.D., a professor of botany and plant pathology.

He explains that small-interfering RNAs (siRNAs) play a normal role in plant development by shutting off genes involved in primary cell wall growth in order to begin development of thicker, secondary cell walls.

“These small RNAs were known to play a role in fending off disease-causing pathogens, but we are only now beginning to understand their involvement in normal plant development,”  he says.

Dr. Carpita’s research team reported its findings in the December 15 early online issue of the Proceedings of the National Academy of Sciences.

“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,”  continues Dr. Carpita.

Viral-Induced Gene Silencing

Mick Held, Ph.D., a postdoctoral researcher in Dr. Carpita’s lab, virologist Steve Scofield, Ph.D., a U.S. Department of Agriculture research scientist and adjunct assistant professor of agronomy at Purdue, and Dr. Carpita made the discovery in barley after introducing Barley Stripe Mosaic virus as a way to “silence” specific genes and study their functions. The researchers noticed that the virus had more effect than anticipated.

“The virus hijacked a whole suite of genes, and when we compared the targeted plant to our control plants we found that the small RNAs were responsible and already in the controls even without adding the virus,”  explains Dr. Held.

Dr. Carpita says the finding allowed researchers to see that the siRNAs, among other things, regulate and shut down primary cell wall development to begin secondary wall growth. “These secondary stages result in characteristics such as tough rinds of corn stalks, vascular elements to conduct water, and fibers for strength,” he notes.

The researchers believe that delaying or preventing the shutdown of both primary and secondary cellulose production might enhance total plant biomass.

“Most biofuel researchers believe that cellulose utilization offers the best path to sustainable ethanol production,” says Dr. Scofield.  “Our work uncovered a previously unknown mechanism that suggests a way to increase the amount of cellulose produced in plants.”

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