Effects on Lignin Structure of Coumarate 3-Hydroxylase Downregulation in Poplar
- PDF / 1,266,172 Bytes
- 11 Pages / 595.276 x 790.866 pts Page_size
- 42 Downloads / 190 Views
Effects on Lignin Structure of Coumarate 3-Hydroxylase Downregulation in Poplar John Ralph & Takuya Akiyama & Heather D. Coleman & Shawn D. Mansfield
Published online: 24 May 2012 # The Author(s) 2012. This article is published with open access at Springerlink.com
Abstract 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 J. Ralph Department of Biochemistry, Enzyme Institute, University of Wisconsin-Madison, 1710 University Avenue, Madison, WI 53726, USA J. Ralph Department of Biological Systems Engineering, University of Wisconsin-Madison, 460 Henry Mall, Madison, WI 53706, USA J. Ralph (*) DOE Great Lakes Bioenergy Research Center, and Wisconsin Bioenergy Initiative, University of Wisconsin-Madison, Madison, WI 53706, USA e-mail: [email protected] URL: http://www.biochem.wisc.edu/faculty/ralph/ URL: http://www.greatlakesbioenergy.org/ T. Akiyama Wood Chemistry Laboratory, Department of Biomaterial Sciences, the University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan e-mail: [email protected] H. D. Coleman Department of Biology, Syracuse University, 460 Life Sciences Complex, 107 College Place, Syracuse, NY 13244, USA e-mail: [email protected] S. D. Mansfield Department of Wood Science, University of British Columbia, Vancouver, BC V6T 1Z4, Canada e-mail: [email protected] URL: http://farpoint.forestry.ubc.ca/FP
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. Keywords Gene downregulation . NMR . Thioacidolysis . Digestibility . Biomass conversion . Lignin composition
Introduction The impact of perturbing lignification has been studied in several plant species using a variety of genomic strategies [1–10]. One of the early enzymes in the pathway is 4coumarate 3-hydroxylase (C3H), a crucial hydroxylase that provides entry to the synthesis of guaiacyl (G) and syringyl (S) lignin precursors from the non-methoxylated p-hydroxyphenyl (H) branch of the pathway (Fig. 1). Guaiacyl and syringyl subunits dominate the structural composition
Data Loading...
