Submitted to: International Symposium on Wood and Pulping Chemistry
Publication Type: Abstract only
Publication Acceptance Date: 2/28/2003
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: A promoter-trap screen allowed us to identify an Arabidopsis line deficient in the caffeic acid O-methyltransferase 1 (COMT) activity. The Atomt1 line is a knockout mutant and the expression profile of the AtOMT1 gene has been determined as well as the consequences of the mutation on lignins, on soluble phenolics and on cell wall digestibility. In this mutant and relative to the wild type, lignins lack syringyl (S) units and contain more 5-hydroxyguaiacyl units (5-OH-G), the precursors of S-units. This altered lignin structure is associated with an improved cell wall digestibility of the dry rachis. The sinapoyl ester pool is modified with a two-fold reduction of sinapoyl-malate in the leaves and stems of mature plants as well as in two week-old seedlings. In addition, the LC-MS analysis of the soluble phenolics extracted from the seedlings reveals the occurrence of unusual derivatives assigned to 5-OH-feruloyl malate and to 5-OH-feruloyl glucose. Therefore, AtOMT1 enzymatic activity appears to be involved not only in lignin formation but also in the biosynthesis of sinapate esters. A poplar cDNA encoding a caffeic acid OMT was successfully used to complement the Atomt1 mutant and restored both the level of S units and of sinapate esters to the control level.