Purdue University researchers found a mechanism that naturally shuts down
cellulose production in plants, and learning how to keep that switch turned
on may be key to enhancing biomass production for plant-based biofuels.

Nicholas Carpita, a professor of botany and plant pathology, said 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 said.

Carpita's research team reported its findings in Monday's (Dec. 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," Carpita said.

Mick Held, a postdoctoral researcher in Carpita's lab, virologist Steve
Scofield, a U.S. Department of Agriculture research scientist and adjunct
assistant professor of agronomy at Purdue, and Carpita made the discovery in
barley after introducing a virus as a way to "silence" specific genes and
study their functions. The researchers noticed that the virus had more
effect then 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," Held
said.

Carpita said this let researchers 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
said.

The researchers said 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," Scofield said. "Our work uncovered
a previously unknown mechanism that suggests a way to increase the amount of
cellulose produced in plants."

Other members of the research team were Bryan Penning and Sarah Kessans of
Purdue and Amanda Brandt of the USDA/Ag Research Service, Crop Production
and Pest Control Research Unit located at Purdue.

The research was funded by a U.S. Department of Energy, Energy Biosciences
grant.
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