Gene Stacking Improves Arabidopsis as Feedstock for Biofuel Production

Lignocellulosic biomass contains high levels of pentose, making it difficult to convert into biofuels than hexose. Thus, increasing the hexose/pentose ratio in biomass is one approach for improvement. The team of Henrik V. Scheller from Joint Bioenergy Institute used genetic engineering to study if the pectic galactan levels can be increased in cell walls of Arabidopsis cells.

The team first overexpressed different plant UDP-glucose 4-epimerases (UGEs) in Arabidopsis. However, no plant UGE could increase the cell wall galactose. The team then simultaneously overexpressed AtUGE2 and the β-1,4-galactan synthase GalS1. This led to an over 80% increase in cell wall galactose in stems. Furthermore, AtUGE2 and GalS1 overexpression in combination with overexpression of the NST1 master regulator for secondary cell wall biosynthesis resulted in thicker of fiber cell walls with high galactose levels. Immunofluorescence microscopy confirmed that increased galactose was present in secondary cell walls.

Simultaneous overexpression of AtUGE2 and GalS1 increased the cell wall galactose compared to the overexpression obtained in either one, alone. The increased galactan in fiber cells also had no impact on plant development. Thus, the gene stacking approach is promising in engineering feedstocks for biofuels.