Researchers at North Carolina State University led by NC State CRISPR¬†pioneer Rodolphe Barrangou and tree geneticist Jack Wang have developed poplar trees with reduced levels of lignin using a CRISPR gene editing¬†system.
The research team used predictive modeling to lower lignin levels, increase the carbohydrate to lignin (C/L) ratio, and increase the ratio of two important lignin building blocks ‚?? syringyl to guaiacyl (S/G) ‚?? in poplar trees. The team used a machine-learning model to sort through almost 70,000 different gene editing strategies targeting 21 important genes¬†associated with lignin production. They then selected the seven best strategies that would lead to trees with 35% less lignin than wild, or unmodified, trees; C/L ratios that were more than 200% higher than wild trees; S/G ratios that were also more than 200% higher than wild trees; and tree growth rates that were similar to wild trees.
From the seven strategies, the researchers used CRISPR gene editing to produce 174 lines of poplar trees. Six months later, the trees had reduced lignin content by up to 50% in some varieties, as well as a 228% increase in the C-L ratio in others. The researchers found more significant lignin reductions in trees with four to six gene edits, while trees with three gene edits showed lignin reduction of up to 32%. Single-gene edits failed to reduce lignin content much at all, which indicates that multigene changes using CRISPR could confer advantages in fiber production.