A new study has found how poplar trees can naturally adjust a key part of their wood chemistry based on changes in their environment.
The discovery by researchers at the University of Missouri, in collaboration Oak Ridge National Laboratory and the University of Georgia, found lignin, an abundant natural substance found in almost every plant containing stems, roots and leaves, helps plants stay upright, move water and protect themselves from temperature changes and other environmental factors.
Poplar demand
Poplar trees are useful for scientific research because their genome has been fully mapped. This additional knowledge allowed collaborators to discover the chemical makeup of lignin changes based on a tree’s latitude.
The researchers examined 430 wood samples from Populus trichocarpa, a poplar tree species that grows primarily in western North America from northern California to British Columbia in Canada.
The trees growing in warmer climates produced lignin with a higher ratio of syringyl-to-guaiacyl (S/G), two key chemical building blocks called monomers, compared with those from colder climates.
In addition to the genetic study, the research team used 3D computer modelling to better understand their findings.
“We identified a mutation in an important cell-wall enzyme in poplar trees called ‘laccase’, which was found to control the S/G ratio in this natural population,” Rachel Weber, a senior biochemistry student at Mizzou who built the model, said. “So, I was able to utilise a protein structural modelling software called ColabFold to pinpoint the exact location of this mutation within the laccase protein.”
Unexpected
To the team’s surprise, the mutation didn’t show up within the active centre of the protein, suggesting the deposition of lignin in natural settings may be regulated by still uncharacterised signaling pathways.
“This points to a more complex regulation than we initially thought and gives us new clues about how trees adapt and protect themselves,” she said. “This knowledge will help us develop additional hypotheses about how this protein functions and interacts with the plant’s surrounding environment.”
Future
Looking ahead, the team is now working to genetically engineer poplar trees and soybeans so they can contain more C-lignin, making the biomass of these plants easier to process into next-generation biorefineries.
The study, Factors underlying a latitudinal gradient in S/G lignin monomer radio in natural poplar variants, was published in the journal Proceedings of the National Academy of Sciences.
Co-authors are Yen On Chan and Ganesh Panzade at the MU Institute for Data Science and Informatics; Trupti Joshi at the Christopher S. Bond Life Sciences Center and Mizzou’s Department of Biomedical Informatics, Biostatistics and Medical Epidemiology; Jin Zhang, Mengjun Shu, Connor Cooper, Russell Davidson, Jerry Parks, Gerald Tuskan and Wellington Muchero at Oak Ridge National Laboratory; Richard Dixon at the University of North Texas and Pradeep Kumar Prabhakar and Beeanna Urbanowicz at the University of Georgia.