CCoAOMT suppression modifies lignin composition in Pinus radiata
| Autor: | Lana Pears, Yuki Tobimatsu, Heather Flint, Lorelle Phillips, Lloyd Donaldson, Armin Wagner, John Ralph, Kirk M. Torr |
|---|---|
| Rok vydání: | 2011 |
| Předmět: |
Radiata
fungi technology industry and agriculture food and beverages Xylem Alcohol macromolecular substances Cell Biology Plant Science Biology biology.organism_classification complex mixtures chemistry.chemical_compound chemistry Biochemistry Polymerization Genetics Methyl caffeate Caffeic acid Lignin Organic chemistry Composition (visual arts) |
| Zdroj: | The Plant Journal. 67:119-129 |
| ISSN: | 0960-7412 |
| DOI: | 10.1111/j.1365-313x.2011.04580.x |
| Popis: | A cDNA clone encoding the lignin-related enzyme caffeoyl CoA 3-O-methyltransferase (CCoAOMT) was isolated from a Pinus radiata cDNA library derived from differentiating xylem. Suppression of PrCCoAOMT expression in P. radiata tracheary element cultures affected lignin content and composition, resulting in a lignin polymer containing p-hydroxyphenyl (H), catechyl (C) and guaiacyl (G) units. Acetyl bromide-soluble lignin assays revealed reductions in lignin content of up to 20% in PrCCoAOMT-deficient transgenic lines. Pyrolysis-GC/MS and 2D-NMR studies demonstrated that these reductions were due to depletion of G-type lignin. Correspondingly, the proportion of H-type lignin in PrCCoAOMT-deficient transgenic lines increased, resulting in up to a 10-fold increase in the H/G ratio relative to untransformed controls. 2D-NMR spectra revealed that PrCCoAOMT suppression resulted in formation of benzodioxanes in the lignin polymer. This suggested that phenylpropanoids with an ortho-diphenyl structure such as caffeyl alcohol are involved in lignin polymerization. To test this hypothesis, synthetic lignins containing methyl caffeate or caffeyl alcohol were generated and analyzed by 2D-NMR. Comparison of the 2D-NMR spectra from PrCCoAOMT-RNAi lines and synthetic lignins identified caffeyl alcohol as the new lignin constituent in PrCCoAOMT-deficient lines. The incorporation of caffeyl alcohol into lignin created a polymer containing catechyl units, a lignin type that has not been previously identified in recombinant lignin studies. This finding is consistent with the theory that lignin polymerization is based on a radical coupling process that is determined solely by chemical processes. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Plný text