Fibres from wood are used for making paper, packaging and textiles, and there is strong interest in optimizing the properties of wood trees for fibre generation. A sticking point has been lignin — a polymer in the cell walls of vascular plants that must be cleaved or solubilized before fibres can be processed. Current methods for removing lignin are energetically and chemically costly, and attempts at genetic optimization of trees for lower-lignin wood have been hampered by the structural and regulatory complexity of lignin biosynthesis. Writing in Science, Sulis et al. make a radical departure from such single-gene attempts by using multiplex CRISPR-based gene editing. The authors first used a model to explore over 69,000 combinations of gene loss-of-function, editing and/or overexpression of 21 genes involved in lignin biosynthesis. From this, they identified seven genome-editing strategies that were predicted to provide desirable properties, including less lignin overall, a higher ratio of carbohydrate to lignin, a higher ratio of the lignin subunits syringyl to guaiacyl, and maintained tree growth. Using CRISPR editing, they then generated 174 variants of the wood tree poplar, which produced wood with substantially altered chemical and physical properties, including lignin reduction of up to 32% following edits to only three genes. The authors present modelling that demonstrates the potential reductions in carbon emissions from wood-pulp production using these CRISPR-edited variants. Breeding such trees may enable greater yields per land area as well as lower energy usage and carbon emissions of the pulping process.
Original reference: Science 381, 216–221 (2023)
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