Improved sugar release from lignocellulosic material by introducing a tyrosine-rich cell wall peptide gene in poplar

Lignin degradation is of critical importance in biomass utilization of woody plants, because the presence of lignin limits hydrolytic enzyme access to cellulose and hemi-cellulose. To date, strategies for lignin removal have ranged from treatment with lignin-degrading fungi to genetic manipulations that reduce lignin content or modify monolignol composition. However, reducing lignin content without compromising tree fitness can be difficult. An alternate approach to modify lignin composition by introducing in situ peptide cross-links is reported here. The hypothesis was that introducing in situ peptide cross-links would not change overall lignin content or distribution in the cell wall, yet should render the lignin more susceptible to protease digestion. To test this, a transgene encoding a high tyrosine-content peptide was designed to express in lignifying tissues of hybrid poplar. Relative to wildtypes, the transgenics had no change in total lignin content or overall plant morphology, although the wood in a number of lines had reduced storage modulus. As predicted, a number of transgenic lines were more susceptible to protease digestion than wildtypes, resulting in a higher polysaccharide release from the lignocellulose complexes. Although pre-liminary, these results suggest that this may be a viable means to facilitate lignin removal and potentially advance the utilization of woody biomass as a biofuel feed-stock.