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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #123834
Title: LIGNIN CHARACTERIZATION IN POPLAR AND ARABIDOPSIS PLANTS WITH DEPRESSED COMT OR CAD ACTIVITY

Author
item JOUANIN, LISE - INRA-VERSAILLES, FRANCE
item GOUJON, THOMAS - INRA-VERSAILLES-FRANCE
item SIBOUT, RICHARD - INRA-VERSAILLES,FRANCE
item POLLET, BRIGITTE - INRA-GRIGNON,FRANCE
item MILA, ISABELLE - INRA-GRIGNON,FRANCE
item LEPLE, CHARLES - INRA-OLIVET,FRANCE
item PILATE, GILLES - INRA-OLIVET,FRANCE
item PETIT-CONIL, MICHEL - CTP,GRENOBLE,FRANCE
item Ralph, John
item LAPPIERRE, CATHERINE - INRA-GRIGNON,FRANCE

Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 7/22/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Lignification, a major biological event in the plant kingdom, is still poorly understood due to the structural complexity and to the high variability of native lignins. Poplars underexpressing enzymes of the monolignol biosynthetic pathway (OMT or CAD) or Arabidopsis thaliana knock-out T-DNA insertion mutants in the genes encoding these enzymes have been obtained and analyzed for the quantity and quality of their lignin. COMT or CAD down-regulation was found to induce specific alterations in lignin structure due to the incorporation of unusual phenolics in the polymer. We have delineated the specific structural traits of lignins, which account for higher (CAD deficiency) or lower (COMT deficiency) susceptibility to alkaline delignification processes. Lignins of COMT depressed plants essentially comprise guaiacyl units together with substantial amounts of 5-hydroxyguaiacyl units and small amounts of syringyl units. They display a higher frequency of resistant interunit bonds and a lower frequency of free phenolic lignin units. These changes make the lignin polymer less amenable to alkaline delignification. Lignins of CAD deficient plants both display a higher content in free phenolic groups and a greater solubility in diluted alkali at room temperature. This is indicative of a more fragmented lignin network. This macromolecular trait is associated with the incorporation of sinalpaldehyde units into the lignin polymer which somehow hinder their peroxidase-driven growth. Interestingly, the level of coniferaldehyde units is not affected by CAD deficiency, which shows that down-regulating CAD activity in poplar and in Arabidopsis specifically affects the reduction of sinapaldehyde into sinapyl alcohol.