title: Changes in Cell Wall Polymers and Degradability in Maize Mutants Lacking 3'- and 5'-O-Methyltransferases Involved in Lignin Biosynthesis.
abstract: Caffeoyl coenzyme A 3-O-methyltransferase (CCoAOMT) and caffeic acid-O-methyltransferase (COMT) are key enzymes in the biosynthesis of coniferyl and sinapyl alcohols, the precursors of guaiacyl (G) and syringyl (S) lignin subunits. The function of these enzymes was characterized in single and double mutant maize plants. In this work, we determined that the comt (brown-midrib 3) mutant plants display a reduction of the flavonolignin unit derived from tricin (a dimethylated flavone), demonstrating that COMT is a key enzyme involved in the synthesis of this compound. In contrast, the ccoaomt1 mutants display a wild-type amount of tricin, suggesting that CCoAOMT1 is not essential for the synthesis of this compound. Based on our data, we suggest that CCoAOMT1 is involved in lignin biosynthesis at least in midribs. The phenotype of ccoaomt1 mutant plants displays no alterations, and their lignin content and composition remain unchanged. On the other hand, the ccoaomt1 comt mutant displays phenotypic and lignin alterations similar to those already described for the comt mutant. Although stems from the three mutants display a similar increase of hemicelluloses, the effect on cell wall degradability varies, the cell walls of ccoaomt1 being the most degradable. This suggests that the positive effect of lignin reduction on cell wall degradability of comt and ccoaomt1 comt mutants is counteracted by changes occurring in lignin composition, such as the decreased S/G ratio. In addition, the role of the flavonolignin unit derived from tricin in cell wall degradability is also discussed.
authors.affiliation: Centre for Research in Agricultural Genomics (CRAG) Consorci CSIC-IRTA-UAB-UB Edifici CRAG Campus de Bellaterra de la UAB, Cerdanyola del Valles, Barcelona, Spain.
authors.forename: Silvia
authors.initials: S
authors.lastname: Fornalé
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, Av. Reina Mercedes, Seville, Spain.
authors.forename: Jorge
authors.initials: J
authors.lastname: Rencoret
authors.affiliation: Área de Fisiología Vegetal, Universidad de León, León, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: García-Calvo
authors.affiliation: Área de Fisiología Vegetal, Universidad de León, León, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Encina
authors.affiliation: Centre for Research in Agricultural Genomics (CRAG) Consorci CSIC-IRTA-UAB-UB Edifici CRAG Campus de Bellaterra de la UAB, Cerdanyola del Valles, Barcelona, Spain.
authors.forename: Joan
authors.initials: J
authors.lastname: Rigau
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, Av. Reina Mercedes, Seville, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Gutiérrez
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla, CSIC, Av. Reina Mercedes, Seville, Spain.
authors.forename: José Carlos
authors.initials: JC
authors.lastname: Del Río
authors.affiliation: Centre for Research in Agricultural Genomics (CRAG) Consorci CSIC-IRTA-UAB-UB Edifici CRAG Campus de Bellaterra de la UAB, Cerdanyola del Valles, Barcelona, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Caparros-Ruiz
mesh_terms: D002473:Cell Wall / Q000378:metabolism*; D005419:Flavonoids / Q000378:metabolism; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011108:Polymers / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism; D003313:Zea mays / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*
chemical_list: D005419:Flavonoids; D010940:Plant Proteins; D011108:Polymers; D011134:Polysaccharides; C017769:tricin; D008780:Methyltransferases
keywords: Cell wall polysaccharides; Lignin; Maize; Methyltransferases; Tricin