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    Author(s): John Ralph; Takuya Akiyama; Hoon Kim; Fachuang Lu; Sally A. Ralph; Clint Chapple; Ramesh B. Nair; Armin Wagner; Fang Chen; M.S. Srinivasa Reddy; Richard A Dixon; Heather D. Coleman; Shawn D. Mansfield
    Date: 2006
    Source: Polyphenols communications 2006 : XXIII International Conference on Polyphenols, Winnipeg, Manitoba, Canada, August 22-25, 2006. [Winnipeg] : University of Manitoba, [2006]: ISBN: 0978158903: 9780978158903: [2] pages.
    Publication Series: Miscellaneous Publication
    PDF: View PDF  (286 KB)

    Description

    Down-regulation of the gene encoding 4-coumarate 3-hydroxylase (C3H) in angiosperms massively but predictably increased the proportion of p-hydroxyphenyl (P) units relative to the normally dominant syringyl (S) and guaiacyl (G) units. Alfalfa stem levels of up to ~65% P (from wild-type (WT) levels of ~1%) resulting from down-regulation of C3H were measured by traditional degradative analyses as well as 2D 13C– 1H correlative NMR methods. Such levels put these transgenics well beyond the P:G:S compositional bounds of normal plants. NMR also revealed structural differences in the interunit linkage distribution that characterizes a lignin polymer. Less severely elevated P-levels were also detected in C3H-downreulated poplar and in HCT-downregulated P. radiata tracheid cultures, but with different structural effects. The compositional and structural changes remain consistent with the existing theory of lignification based on combinatorial radical coupling reactions under simple chemical control. Such structural differences form a basis for explaining differences in digestibility and pulping performance of C3H/HCT-deficient plants.

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    Citation

    Ralph, John; Akiyama, Takuya; Kim, Hoon; Lu, Fachuang; Ralph, Sally A.; Chapple, Clint; Nair, Ramesh B.; Wagner, Armin; Chen, Fang; Reddy, M.S. Srinivasa; Dixon, Richard A; Coleman, Heather D.; Mansfield, Shawn D. 2006. Lignification in transgenics deficient in 4-coumarate 3-hydroxylase (C3H)or the associated hydroxycinnamoyl transferase (HCT). Polyphenols communications 2006 : XXIII International Conference on Polyphenols, Winnipeg, Manitoba, Canada, August 22-25, 2006. [Winnipeg] : University of Manitoba, [2006]: ISBN: 0978158903: 9780978158903: [2] pages.

    Keywords

    Biosynthesis, enzymes, biotechnology, nuclear magnetic resonance spectroscopy, lignin analysis, genetic engineering, coumarins, lignification, pulping, alfalfa, transgenic plants, poplar, Pinus radiata, down-regulation, pulp and paper processes, guaiacyl, syringyl, coumarate 3-hydroxylate, hydroxyphenyl

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https://www.fs.usda.gov/treesearch/pubs/27092