Trees are a—sometimes surprising—source of many products in our daily lives, including paper, packaging, nappies, and even clothes. Now a team of researchers prove they can edit tree genes to significantly amp up the amount of fiber pulp extracted from trees by 40%, making the pulp industry more efficient and even slashing its greenhouse gas emissions.
This genetic breakthrough was built on previous research that identified an ingredient in trees called lignin as a hurdle to plentiful fiber production. Lignin boosts the sturdiness of trees as they grow. But this trait also makes it very resistant to breakdown. When it occurs at high volumes in wood, lignin reduces the amount of fiber that pulping plants can get out of a tree.
Lignin, then, was the researchers’ target: they embarked on an experiment to breed trees with a genetic combination that would lower its presence in wood, while boosting the amount of carbohydrates that create fiber at the same time.
This double-whammy involved a hugely ambitious gene sequencing effort, focused on poplar trees. Using machine learning, they mapped out almost 70,000 potential ways they could edit these poplar tree genes to achieve the lignin-reducing and carbohydrate-boosting features they were looking for. That survey helped identify key gene combinations that were most likely to create these desirable traits, as well as the editing strategies that would work to get them.
Using that information, the researchers homed in on seven of the most promising editing strategies, and then used CRISPR—an editing technique that precisely cuts DNA—to make the required changes to the trees’ genomes. This process resulted in 174 new poplar variants, which the researchers then raised in a controlled greenhouse environment.
When they sampled their grown trees, what they discovered was a startling change in their makeup. In some tree lines, the lignin content had declined by 32%, and some up to 50%; the more gene edits they’d made, the lower the amount of lignin the tree contained, it turned out.
Certain variants also showed a 228% increase in the ratio of carbohydrates to lignin in the wood, compared to regular poplar trees. This was a hint that the trees would be highly productive in pulping mills too—an idea the researchers wanted to test out.
Short of going to an actual mill, the next best thing was to build a detailed model that simulated what the engineered trees would yield in a regular processing plant. The results were striking: according to the model the engineered trees could produce 40% more fiber in a pulping mill than you’d get from conventional trees. This came down to a perfect combination of high carbohydrate density which increased the available pulp, and lower lignin which reduced the amount of energy and time that would go into processing the wood—thereby freeing up more of both to extract the more viable pulp.
Meanwhile, reducing the lignin content would also reduce the amount of pulping chemicals that plants need to use, and the more efficient energy use could cut the pulping industry’s global warming potential by 20%.
Overall, the fiber-rich wood could have broad financial benefits too, potentially boosting the industry’s value from $269.2 million to $1856.9 million (calculated based on processing plants that use biomass as a supplementary energy source.)
The test poplar trees will soon be moved into field experiments to see how well they fare out there in the real world. A lot rests on their success: more productive wood could lead to more efficient land-use, and could boost the availability of ingredients to make lower-impact packaging and fabric alternatives—taking ‘sustainable forestry’ to a whole new level.
Wang et. al. “Multiplex CRISPR editing of wood for sustainable fiber production.” Science. 2023.