Stacking of a low-lignin trait with an increased guaiacyl and 5-hydroxyguaiacyl unit trait leads to additive and synergistic effects on saccharification efficiency in .

Background: Lignocellulosic biomass, such as wood and straw, is an interesting feedstock for the production of fermentable sugars. However, mainly due to the presence of lignin, this type of biomass is recalcitrant to saccharification. In Arabidopsis, lignocellulosic biomass with a lower lignin content or with lignin with an increased fraction of guaiacyl (G) and 5-hydroxyguaiacyl (5H) units shows an increased saccharification efficiency. Here, we stacked these two traits and studied the effect on the saccharification efficiency and biomass yield, by combining either (), - (-), or - (-) with - (- or -) mutants.

Results: The three double mutants (-, -- and --) had a decreased lignin amount and an increase in G and 5H units in the lignin polymer compared to wild-type (WT) plants. The - double mutant had a better saccharification efficiency compared to the parental lines when an acid or alkaline pretreatment was used. For the double mutants, -- and --, the saccharification efficiency was significantly higher compared to WT and its parental lines, independent of the pretreatment used. When no pretreatment was used, the saccharification efficiency increased even synergistically for these mutants.

Conclusion: Our results show that saccharification efficiency can be improved by combining two different mutant lignin traits, leading to plants with an even higher saccharification efficiency, without having a yield reduction of the primary inflorescence stem. This approach can help improve saccharification efficiency in bio-energy crops.