title: Caffeoyl coenzyme A O-methyltransferase down-regulation is associated with modifications in lignin and cell-wall architecture in flax secondary xylem.
abstract: 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/Guaïacyl (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.
authors.affiliation: Université Lille 1, F-59655 Villeneuve d'Ascq, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Day
authors.forename: Godfrey
authors.initials: G
authors.lastname: Neutelings
authors.forename: Frédérique
authors.initials: F
authors.lastname: Nolin
authors.forename: Sébastien
authors.initials: S
authors.lastname: Grec
authors.forename: Anouk
authors.initials: A
authors.lastname: Habrant
authors.forename: David
authors.initials: D
authors.lastname: Crônier
authors.forename: Bouchra
authors.initials: B
authors.lastname: Maher
authors.forename: Christian
authors.initials: C
authors.lastname: Rolando
authors.forename: Hélène
authors.initials: H
authors.lastname: David
authors.forename: Brigitte
authors.initials: B
authors.lastname: Chabbert
authors.forename: Simon
authors.initials: S
authors.lastname: Hawkins
mesh_terms: D000595:Amino Acid Sequence; D002473:Cell Wall; D018076:DNA, Complementary; D015536:Down-Regulation / Q000502:physiology; D019597:Flax / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D008031:Lignin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D015591:Microspectrophotometry; D008969:Molecular Sequence Data; D010802:Phylogeny; D030821:Plants, Genetically Modified; D016415:Sequence Alignment; D052584:Xylem / Q000166:cytology*
chemical_list: D018076:DNA, Complementary; D008031:Lignin; D008780:Methyltransferases; C059825:caffeoyl-CoA O-methyltransferase