Effects on Lignin Structure of Coumarate 3-Hydroxylase Downregulation in Poplar

John Ralph, Takuya Akiyama, Heather D. Coleman, Shawn D. Mansfield

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


The lignin structural ramifications of coumarate 3-hydroxylase (C3H) downregulation have not been addressed in hardwoods. Such information is required to accompany an assessment of the digestibility and bioenergy performance characteristics of poplar, in particular. Structurally rich 2D NMR methods were applied to the entire lignin fraction to delineate lignin p-hydroxyphenyl:guaiacyl:syringyl (H:G:S) levels and linkage distribution changes (and to compare with traditional degradative analyses). C3H downregulation reduced lignin levels by half and markedly increased the proportion of H units relative to the normally dominant G and S units. Relative stem H unit levels were up by ~ 100-fold to ~ 31 %, almost totally at the expense of G units; differences in the lignin interunit linkage distributions were more subtle. The H level in the most drastically C3H-downregulated transgenic poplar falls well beyond the H:G:S compositional bounds of normal angiosperms. The response observed here, in poplar, differs markedly from that reported for alfalfa where the S:G ratio remained almost constant even at substantial H levels, highlighting the often differing responses among plant species.

Original languageEnglish (US)
Pages (from-to)1009-1019
Number of pages11
JournalBioenergy Research
Issue number4
StatePublished - Dec 2012


  • Biomass conversion
  • Digestibility
  • Gene downregulation
  • Lignin composition
  • NMR
  • Thioacidolysis

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Agronomy and Crop Science
  • Energy (miscellaneous)


Dive into the research topics of 'Effects on Lignin Structure of Coumarate 3-Hydroxylase Downregulation in Poplar'. Together they form a unique fingerprint.

Cite this