Knock-Down of Galacturonosyltransferase-4 Gene Leads to Reduction in Lignin-Carbohydrate Crosslinking in Switchgrass

The Science

Researchers investigated downregulation of a pectin biosynthetic gene, GAUT4, on the structures of lignin and their importance to the recalcitrance of switchgrass. Thet studied chromatographic and NMR analyses of the molecular structure of lignin and hemicellulose as well as the level of lignin-carbohydrate crosslinking in GAUT4-downregulated switchgrass.

The Impact

• GAUT4-KD lines have a lower abundance of ferulate and lignin-carbohydrate complex cross-linkages, reduced hemicellulose molecular weights, and reduced amounts of residual arabinan and xylan in lignin-enriched fractions, in comparison to the wildtype (WT).
• These structural changes in lignin and hemicellulose lead to a greater coalescence and migration of lignin after hydrothermal pretreatment. The results reveal the roles of both decreased lignin-polymer and pectin cross-links in the reduction of recalcitrance in GAUT4-KD switchgrass.

Summary

Knockdown (KD) expression of GAlactUronosylTransferase 4 (GAUT4) in switchgrass improves sugar yield and ethanol production from the biomass. The reduced recalcitrance of GAUT4-KD transgenic biomass is associated with reduced cell wall pectic homogalacturonan and rhamnogalacturonan II content and cross-linking, and the associated increases in accessibility of cellulose to enzymatic deconstruction.

References

Li, M., C. G. Yoo, Y. Pu, A. K. Biswal, A. L. Tolbert, D. Mohnen, and A. J. Ragauskas. 2019. “Downregulation of Pectin Biosynthesis Gene GAUT4 Leads to Reduced Ferulate and Lignin-Carbohydrate Cross-Linking in Switchgrass,” Communications Biology 2, 22 DOI:10.1038/s42003-018-0265-6.