Scientists unravel more details of plant cell-wall construction

December 13, 2010

UPTON, NY - One big challenge in converting plants to biofuels is that the very same molecules that keep plants standing up make it hard to break them down. Now scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory are unraveling details of how plant cells' structural supports - their cell walls - are made, with the hope of finding ways to change their composition for more efficient biofuel production.

In a paper to be published the week of December 13, 2010, in the Proceedings of the National Academy of Sciences, the researchers describe details of how precursors to lignin, one important cell-wall component, are transported across cellular membranes prior to linking up. The key finding, that the process requires a class of energy-dependent transporter molecules, may provide a "chink in the armor" that opens a way to alter plants' lignin content.

"Being able to manipulate lignin biosynthesis would have a great influence on our ability to produce renewable biofuels from plant cellulosic feedstocks, and could also have a large effect on many other agricultural and industrial processes, such as the production of paper and more digestible foods for grazing animals," said lead author Chang-Jun Liu, a Brookhaven biologist.

Prior to cell-wall construction, lignin precursors known as monolignols are made in the cell's interior cytoplasm. Some precursors may be sequestered in internal vacuoles for storage, while some move out of the cell to link up and form the lignin component of the cell wall - a protective and supportive barrier around the cell. In both cases, the precursors move across a membrane, either out of the cell or into the vacuole. But no one was certain how the process occurred - whether by simple diffusion or via some active transport mechanism.

The Brookhaven team unraveled the mystery by isolating portions of cellular and vacuolar membrane from Arabidopsis and poplar plants, making them into closed vesicles that resemble bubbles, and mixing in pure monolignols and ones that have been chemically modified to form monolignol glucosides, which are commonly observed in some plants. They then monitored which type and how much of each precursor moved across the two kinds of membranes and into the vesicles under a range of conditions, including in the presence of inhibitors for different kinds of transport molecules.

The range of assays revealed that pure monolignols move across the cellular membrane while monolignol glucosides move preferentially into vacuoles. But most importantly, very little of either precursor would move across either type of membrane without the addition of ATP, the molecular "currency" for energy in cells.

"ATP is the energy molecule that is well known for providing the driving force for a group of transporters called ATP-binding cassette (ABC) transporters on cell membranes," Liu said.

To prove the point, adding an agent that specifically inhibits ABC transporters completely blocked uptake of lignin precursors by both types of membrane vesicles.

With these experiments and additional evidence, Liu and his colleagues demonstrated that ABC-like transporters on cell membranes are responsible for the transport of lignin precursors.

Now that the scientists have identified a class of transporters likely involved in sequestering and transporting lignin's building blocks, they'll pursue detailed studies to identify exactly which members of the class are involved.

"If we can identify those particular transporters we might be able to control their expression to reduce the precursor deposited into the cell wall, and thus lower the cell-wall content of lignin -or, selectively control the particular type of precursor deposited to change lignin composition and produce more easily cleavable biopolymers," Liu said.
This work was supported by the DOE Office of Science.

Brookhaven postdoctoral research associate Yu-Chen Miao is a coauthor on the PNAS paper.

Media contacts: Karen McNulty Walsh,, (631) 344-8350 or Peter Genzer,, (631) 344-3174

An electronic version of this news release with related graphics is available online at: Prior to the embargo time, reporters will be required to enter a password for access. The case-sensitive password is: BNLnews.

Related LinksOne of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. Brookhaven is operated and managed for DOE's Office of Science by Brookhaven Science Associates, a limited-liability company founded by the Research Foundation of State University of New York on behalf of Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

Visit Brookhaven Lab's electronic newsroom for links, news archives, graphics, and more at , or follow Brookhaven Lab on Twitter,

DOE/Brookhaven National Laboratory

Related Lignin Articles from Brightsurf:

Utilizing a 'krafty' waste product: Toward enhancing vehicle fuel economy
Researchers from Kanazawa University have chemically modified Kraft lignin -- ordinarily considered in the paper industry to be a waste product -- and used it to produce quality carbon fiber.

CRISPRing trees for a climate-friendly economy
Researchers led by prof. Wout Boerjan (VIB-UGent Center for Plant Systems Biology) have discovered a way to stably finetune the amount of lignin in poplar by applying CRISPR/Cas9 technology.

New process boosts lignin bio-oil as a next-generation fuel
A new low-temperature multi-phase process for upgrading lignin bio-oil to hydrocarbons could help expand use of the lignin, which is now largely a waste product left over from the productions of cellulose and bioethanol from trees and other woody plants.

Lightweight green supercapacitors could charge devices in a jiffy
In a new study, researchers at Texas A&M University have described their novel plant-based energy storage device that could charge even electric cars within a few minutes in the near future.

From biopaste to bioplastic
Forest scientists develop innovative wood-based materials for 3D printing.

Key technology for mass-production of lignin-bio-aviation fuels for reducing greenhouse gas
The team, led by Dr. Jeong-Myeong Ha of the Clean Energy Research Center at the Korea Institute of Science and Technology(KIST), has developed a technology that can be used to mass-produce aviation-grade fuels from wood wastes.

Researchers develop sustainable method for extracting vanillin from wood processing waste
Scientists at Johannes Gutenberg University Mainz (JGU) in Germany have developed a new sustainable method of extracting the flavoring agent vanillin from lignin, a component of wood.

A model for better predicting the unpredictable byproducts of genetic modification
Researchers are interested in genetically modifying trees for a variety of applications, from biofuels to paper production.

A novel biofuel system for hydrogen production from biomass
A recent study, affiliated with South Korea's Ulsan National Institute of Science and Technology (UNIST) has presented a new biofuel system that uses lignin found in biomass for the production of hydrogen.

Plastic from wood
The biopolymer lignin is a by-product of papermaking and a promising raw material for manufacturing sustainable plastic materials.

Read More: Lignin News and Lignin Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to