Scientists studying plant cell walls—structural supports that help plants overcome the downward pull of gravity—have discovered mechanistic details of a protein involved in the assembly of lignin, a key cell-wall component. The protein acts as a targeted “electron shuttle,” delivering the “fuel” that drives the construction of one specific type of lignin building block.
The study, published in The Plant Cell by scientists from Stony Brook University, Brookhaven National Laboratory and their collaborators, revealed that this particular electron shuttle was different from those that drive the production of other kinds of lignin precursors, said Chang-Jun Liu, a BNL scientist who also holds an adjunct position at Stony Brook University and who led the research.
These findings suggest that controlling the relative abundance of electron shuttle proteins could be a new strategy for steering which cell-wall building blocks are put in place as plants grow.
Traditionally, scientists have sought to control the mix of lignin and other cell-wall building blocks by focusing on the allocation of carbon, the essential backbone of all these molecules. The idea is to drive carbon into molecules that would be useful for specific applications.
For example, a certain mix of lignin building blocks could make cell walls easier to break down to increase the efficiency of converting biomass to biofuels. An abundance of one particular lignin polymer, on the other hand, could be used for making carbon fibers or high-value aromatic compounds for flavors and fragrances.
“Much of this previous work has directly targeted the enzymes that steer carbon into different biochemical pathways,” said Liu.
The new work suggests an alternative approach, targeting the shuttle proteins that deliver the electrons needed to activate the enzymes.
“Electrons are like the fuel for the reaction,” Liu explained. “For these enzymes, without this fuel, these reactions cannot happen. By targeting the electron-delivery proteins, we can selectively redirect the electron flow to change plants’ lignin composition.”