title: Signatures of cinnamyl alcohol dehydrogenase deficiency in poplar lignins.
abstract: A series of transgenic poplars down-regulated for cinnamyl alcohol dehydrogenase (CAD) was analyzed by thioacidolysis. Among the lignin-derived monomers, the indene compounds that were recently shown to originate from sinapaldehyde incorporated into lignins through 8-O-4-cross-coupling, were found to increase as a function of CAD deficiency level. While these syringyl markers were recovered in substantial amounts in the most severely depressed lines, the markers for coniferaldehyde incorporation were recovered in only low amounts. In conjunction with these additional sinapaldehyde units and relative to the control samples, lignins in CAD-deficient poplar lines had less conventional syringyl-units and beta-O-4-bonds and more free phenolic groups. We found that almost half of the polymers in the most deficient lines could be solubilized in alkali and at room temperature. This unusual behavior suggests that lignins in CAD-deficient poplars occur as small, alkali-leachable lignin domains. That mainly sinapaldehyde incorporates into the lignins of CAD-deficient poplars suggests that the recently identified sinapyl alcohol dehydrogenase (SAD), which is structurally distinct from the CAD enzyme targeted herein, does not play any substantial role in constitutive lignification in poplar.
authors.affiliation: UMR 206 INRA-INAPG Chimie Biologique, Institut National Agronomique, F-78850 Thiverval-Grignon, France. lapierre@grignon.inra.fr
authors.forename: Catherine
authors.initials: C
authors.lastname: Lapierre
authors.forename: Gilles
authors.initials: G
authors.lastname: Pilate
authors.forename: Brigitte
authors.initials: B
authors.lastname: Pollet
authors.forename: Isabelle
authors.initials: I
authors.lastname: Mila
authors.forename: Jean-Charles
authors.initials: JC
authors.lastname: Leplé
authors.forename: Lise
authors.initials: L
authors.lastname: Jouanin
authors.forename: Hoon
authors.initials: H
authors.lastname: Kim
authors.forename: John
authors.initials: J
authors.lastname: Ralph
mesh_terms: D000171:Acrolein / Q000031:analogs & derivatives* / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000172:deficiency* / Q000378:metabolism; D002625:Chemistry, Organic / Q000379:methods; D015536:Down-Regulation; D008401:Gas Chromatography-Mass Spectrometry; D008031:Lignin / Q000096:biosynthesis / Q000737:chemistry*; D015394:Molecular Structure; D010641:Phenotype; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D032107:Populus / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D012972:Sodium Hydroxide / Q000737:chemistry; D012995:Solubility; D014934:Wood
chemical_list: C075386:sinapaldehyde; D012972:Sodium Hydroxide; D000171:Acrolein; D008031:Lignin; D000429:Alcohol Oxidoreductases; C018656:cinnamyl alcohol dehydrogenase