Skip to page content
USDA Forest Service
  
Treesearch

Research & Development Treesearch

 
Treesearch Home
About Treesearch
Contact Us
Research & Development
Forest Products Lab
International Institute of Tropical Forestry
Northern
Pacific Northwest
Pacific Southwest
Rocky Mountain
Southern Research Station
Help
 

Science.gov - We Participate


USA.gov  Government Made Easy


Global Forest Information Service

US Forest Service
P.O. Box 96090
Washington, D.C.
20090-6090

(202) 205-8333

You are here: Home / Search / Publication Information
Bookmark and Share

Publication Information

View PDF (501 KB bytes)

Title: Effects of coumarate 3-hydroxylase down-regulation on lignin structure

Author: Ralph, John; Akiyama, Takuya; Kim, Hoon; Lu, Fachuang; Schatz, Paul F.; Marita, Jane M.; Ralph, Sally A.; Reddy, M.S. Srinivasa; Chen, Fang; Dixon, Richard A.;

Date: 2006

Source: Journal of biological chemistry. Vol. 281, no. 13 (Mar. 31, 2006): pages 8843-8853

Publication Series: Miscellaneous Publication

Description: Down-regulation of the gene encoding 4-coumarate 3-hydroxylase (C3H) in alfalfa massively but predictably increased the proportion of p-hydroxyphenyl (P) units relative to thenormally dominant guaiacyl (G) and syringyl (S) units Stem levels of up to ~65% P (from wild-type levels of ~1%) resulting from down-regulation of C3H were measured by traditional degradative analyses as well as two-dimensional 13C-1H correlative NMR methods. Such levels put these transgenics well beyond the P:G:S compositional bounds of normal plants; p-hydroxyphenyl levels are reported to reach a maximum of 30% in gymnosperm severe compression wood zones but are limited to a few percent in dicots. NMR also revealed structural differences in the interunit linkage distribution that characterizes a lignin polymer. Lower levels of key b-aryl ether units were relatively augmented by higher levels of phenylcoumarans and resinols. The C3H- eficient alfalfa lignins were devoid of b-1 coupling products, highlighting the significant differences in the reaction course for p- coumaryl alcohol versus the two normally dominant monolignols, coniferyl and sinapyl alcohols. A larger range of dibenzodioxocin structures was evident in conjunction with an approximate doubling of their proportion. The nature of each of the structural units was revealed by long range 13C-H correlation experiments. For example, although 8-ethers resulted from the coupling of all three monolignols with the growing polymer, phenylcoumarans were formed almost solely from coupling reactions involving p-coumaryl alcohol; they resulted from both coniferyl and sinapyl alcohol in the wild-type plants. Such structural differences form a basis for explaining differences in digestibility and pulping performance of C3H-deficient plants.

Keywords: Down regulation, lignin structure, coumarate, hydroxylase

Publication Notes:

  • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
  • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

XML: View XML

Citation:


Ralph, John; Akiyama, Takuya; Kim, Hoon; Lu, Fachuang; Schatz, Paul F.; Marita, Jane M.; Ralph, Sally A.; Reddy, M.S. Srinivasa; Chen, Fang; Dixon, Richard A. 2006. Effects of coumarate 3-hydroxylase down-regulation on lignin structure. Journal of biological chemistry. Vol. 281, no. 13 (Mar. 31, 2006): pages 8843-8853

 


 [ Get Acrobat ]  Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.