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Sequencing around 5-Hydroxyconiferyl Alcohol-Derived Units in Caffeic Acid O -Methyltransferase-Deficient Poplar Lignins

Fachuang Lu, Jane M. Marita, Catherine Lapierre, Lise Jouanin, Kris Morreel, Wout Boerjan and John Ralph
Plant Physiology
Vol. 153, No. 2 (June 2010), pp. 569-579
Stable URL: http://www.jstor.org/stable/25680876
Page Count: 11
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Sequencing around 5-Hydroxyconiferyl Alcohol-Derived Units in Caffeic Acid
              O
              -Methyltransferase-Deficient Poplar Lignins
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Abstract

Caffeic acid O-methyltransferase (COMT) is a bifunctional enzyme that methylates the 5- and 3-hydroxyl positions on the aromatic ring of monolignol precursors, with a preference for 5-hydroxyconiferaldehyde, on the way to producing sinapyl alcohol. Lignins in COMT-deficient plants contain benzodioxane substructures due to the incorporation of 5-hydroxyconiferyl alcohol (5-OH-CA), as a monomer, into the lignin polymer. The derivatization followed by reductive cleavage method can be used to detect and determine benzodioxane structures because of their total survival under this degradation method. Moreover, partial sequencing information for 5-OH-CA incorporation into lignin can be derived from detection or isolation and structural analysis of the resulting benzodioxane products. Results from a modified derivatization followed by reductive cleavage analysis of COMT-deficient lignins provide evidence that 5-OH-CA cross couples (at its β-position) with syringyl and guaiacyl units (at their O-4-positions) in the growing lignin polymer and then either coniferyl or sinapyl alcohol, or another 5-hydroxyconiferyl monomer, adds to the resulting 5-hydroxyguaiacyl terminus, producing the benzodioxane. This new terminus may also become etherified by coupling with further monolignols, incorporating the 5-OH-CA integrally into the lignin structure.

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