The survival of most plants, including those that people rely on for food, depends on their ability to build strong but flexible cell walls. A key component of these walls is a molecule called xylan.
Now, UGA researchers have discovered two proteins that play a critical role in the formation of this fundamental component of plant life, opening the doors for a new toolkit that one day may help scientists engineer improved plants for biofuels, construction materials, medicine and food production.
“The scientific community has identified a large number of proteins that the plant uses to assemble its cell walls, but it has been very difficult to identify those few proteins that are directly involved in the construction of key polysaccharide (molecules) like xylan,” said Will York, a professor of biochemistry and molecular biology in UGA’s Complex Carbohydrate Research Center and principal investigator of a CCRC research team that recently published the paper describing its results in The Plant Journal.
“The work we’ve done gives us the fundamental knowledge we need to manipulate plants for industry and agriculture,” said York, who is a member of the Bioenergy Science Center.
Plants that don’t make enough xylan have weak cell walls, so they don’t grow normally and cannot transport life-giving water from the roots to the leaves. Xylan is the third most abundant glycopolymer on Earth after cellulose and chitin, and it forms a major component of wood, forage, biomass and dietary fiber.
The construction of plant cells and fibrous tissue is an extraordinarily complicated process involving a huge number of genes that dictate every minute detail of plant growth and development. In that immense sea of biological data, however, are specific genes that are directly responsible for the development of polymers like xylan.
Through collaborations with other researchers at the CCRC, the team was able to identify two proteins, IRX 10-L and ESK1/TBL29, that directly are involved in xylan synthesis.
These genetic processes are not only important for understanding how plants grow, but also how they can be more easily broken down into useful products like biofuels.
Through millions of years of evolution, plants have developed rigid support structures that allow them to grow tall enough for their leaves to efficiently harvest sunlight. These structures are strong and flexible because they contain xylan-rich cell walls. For the plant to survive, these cell walls must also be resistant to attack by insects and microbes.
Overcoming this inherent strength is a major obstacle to the fledgling biofuel industry, because it makes it more difficult to extract the energy-rich sugars locked inside the sturdy plant cells walls. Xylan plays a major role in this resistance, and the researchers hope that their discovery could help alternative energy companies make fuels more efficiently.
But an improved understanding of xylan stands to benefit other industries as well.
Ultimately, more work is needed before their discovery turns into a marketable product or process, but York and his colleagues are optimistic about the future.