Caffeoyl coenzyme A O-methyltransferase down-regulation is associated with modifications in lignin and cell-wall architecture in flax secondary xylem. Day, A., Neutelings, G., Nolin, F., Grec, S., Habrant, A., Cr??nier, D., Maher, B., Rolando, C., David, H., Chabbert, B., & Hawkins, S. Plant Physiology and Biochemistry, 47(1):9-19, 2009.
Caffeoyl coenzyme A O-methyltransferase down-regulation is associated with modifications in lignin and cell-wall architecture in flax secondary xylem [pdf]Paper  doi  abstract   bibtex   
Caffeoyl coenzyme A O-methyltransferase (CCoAOMT, EC 2.1.1.104) down-regulated-flax (Linum usitatissimum) plants were generated using an antisense strategy and functionally characterized. Chemical analyses (acetyl bromide and thioacidolysis) revealed that the lignin quantity was reduced and that the Syringyl/Gua??acyl (S/G) lignin monomer ratio was modified in the non-condensed lignin fraction of two independent down-regulated lines. These modifications were associated with altered xylem organization (both lines), reduced cell-wall thickness (one line) and the appearance of an irregular xylem (irx) phenotype (both lines). In addition UV microspectroscopy also indicated that CCoAOMT down-regulation induced changes in xylem cell-wall structure and the lignin fractions. Microscopic examination also suggested that CCoAOMT down-regulation could influence individual xylem cell size and identity. As a first step towards investigating the cellular mechanisms responsible for the unusual structure of flax lignin (G-rich, condensed), recombinant flax CCoAOMT protein was produced and its affinity for different potential substrates evaluated. Results indicated that the preferred substrate was caffeoyl coenzyme A, followed by 5-hydroxyconiferaldehyde suggesting that flax CCoAOMT possesses a small, but probably significant 5??? methylating activity, in addition to a more usual 3??? methylating activity. ?? 2008 Elsevier Masson SAS. All rights reserved.

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