Wood is an important sustainable biomaterial for construction, bioenergy, and pulp and paper production. Wood is formed from secondary cell walls of vascular plants consisted predominantly of cellulose, hemicelluloses, and lignin. Lignin confers mechanical strength to plant cell walls, hydrophobicity for water transport, and resistance to pests and pathogens. However, the recalcitrance of lignin to enzymatic and chemical degradation limits the extraction of cellulose and other fermentable sugars from lignocellulosic biomass, hindering many industrial processes such as biofuels and pulp production. The genetic manipulation of lignin biosynthesis offers enormous potential to enhance the productivity of wood-derived bioproducts and minimize the use of harsh chemical treatments in delignification. However, the complexity of lignin biosynthetic pathway challenged intuitive genetic modification to improve wood properties and conversion efficiency to bioproducts. Modifying lignin biosynthesis is frequently associated with negative impacts on plant growth and development. Therefore, a systems-based approach to inform concurrent multi-trait engineering strategies using combinations of gene knockout and/or gene overexpression is crucial to maximize wood conversion efficiency and reduce the negative impacts on plant phenotypes. We have recently established a multi-omics integrative model that predicts how changing the expression of lignin genes affects phenotypic traits including wood chemical and physical properties, tree growth, and wood saccharification efficiency. Using this model, we carried out more than 80,000 in silico multigene perturbations for different combinations of lignin gene overexpression and knockout. From these simulations, we identified strategies for simultaneous manipulation of up to six different lignin genes that would reduce lignin content, increase S/G ratio and carbohydrate content, enhance saccharification efficiency, and exhibit no negative growth effects. Based on these multigene engineering strategies, we have generated CRISPR-edited transgenic trees that may exhibit concurrent improvements in wood chemical and physical traits without adverse growth effects.
Coauthors: Chenmin Yang – Forest Biotechnology Group;Barbara Marques – Forest Biotechnology Group;Megan Matthews – Electrical and Computer Engineering;Cranos Willians – Electrical and Computer Engineering;Vincent Chiang – Forest Biotechnology Group;Jack Wang – Forest Biotechnology Group