Evidence for a novel biosynthetic pathway that regulates the ratio of syringyl to guaiacyl residues in lignin in the differentiating xylem of Magnolia kobus DC |
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Authors: | Fang Chen Seiich Yasuda Kazuhiko Fukushima |
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Institution: | (1) Laboratory of Forest Chemistry, Faculty of Agriculture, Nagoya University, Nagoya 464-8601, Japan, JP |
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Abstract: | The biosynthetic pathways to monolignols in Magnolia kobus were investigated by feeding stems with a deuterium-labeled precursor. Pentadeutero γ,γ-2H2, OC2H3] coniferyl alcohol was supplied to shoots of Magnolia kobus and the incorporation of the labeled precursor into lignin was traced by gas chromatography-mass spectrometry. In addition
to the direct incorporation of the labeled precursor into guaiacyl units, we detected a significant amount of pentadeuterium-labeled
syringyl units with two γ-deuterium atoms. The relative level of trideuterium-labeled syringyl monomers (the result of conversion
via the cinnamic acid pathway, in which two γ-deuterium atoms are removed during enzymatic re-oxidation) was negligible. Our
results provide conclusive evidence for a novel alternative pathway for generation of lignin subunits at the monolignol stage
and they suggest that this new pathway might be important for regulation of the composition of lignin.
Received: 21 August 1998 / Accepted: 30 September 1998 |
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Keywords: | : Coniferyl alcohol Lignin biosynthesis Magnolia Sinapyl alcohol |
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