Structural alterations of lignins in transgenic poplars with depressed cinnamyl alcohol dehydrogenase or caffeic acid O-methyltransferase activity have an opposite impact on the efficiency of industrial kraft pulping

• Published in: Plant physiology (Bethesda) Vol. 119; no. 1; pp. 153 - 163
• Main Authors: Lapierre, C, Pollet, B, Petit-Conil, M, Toval, G, Romero, J, Pilate, G, Leple, J.C, Boerjan, W, Ferret, V, Nadai, V. de
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 1999; American Society of Plant Biologists; Oxford University Press ; American Society of Plant Biologists
• Subjects: Agronomy. Soil science and plant productions; alcohol dehydrogenase; Biochemistry and Macromolecular Structure; Biological and medical sciences; biosynthesis; caffeic acid; chemical constituents of plants; Chemical constitution; chemical degradation; cinnamic acid; Colors; Dimers; Down regulation; Economic plant physiology; enzyme activity; Fundamental and applied biological sciences. Psychology; gene expression; gene transfer; genetic regulation; genetic variation; Genetics; genotype; Greenhouses; hybrids; kraft paper; kraft pulping; Life Sciences; Lignin; Monomers; Plant physiology and development; Plants; Plants genetics; Populus alba; Populus tremula; Pulping; transferases; Transgenic plants; Xylem; Lignin; Hybrid variety; Cinnamyl-alcohol dehydrogenase; Production quality; Enzyme; Transferases; Populus tremula; Alteration; Delignification; Salicaceae; Paper industry; Enzymatic activity; Methyltransferases; Efficiency; Dicotyledones; Angiospermae; Hardwood forest tree; Spermatophyta; Chemical composition; Transgenic plant; Oxidoreductases; Structural analysis; Populus alba; PAPIER KRAFT; LIGNIN STRUCTURE; CAD; STRUCTURE DE LA LIGNINE; PEUPLIER; CINNAMYL ALCOHOL DESHYDROGENASE; TRANSGENIC POPLAR; KRAFT PULPING; CAFFEIC ACID O-METHYLTRANSFERASE; COMT; ACIDE CAFFEIQUE O-METHYLTRANSFERASE; LIGNIN BIOSYNTHESIS
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.119.1.153

We evaluated lignin profiles and pulping performances of 2-year-old transgenic poplar (Populus tremula X Populus alba) lines severely, altered in the expression of caffeic acid/5-hydroxyferulic acid O-methyltransferase (COMT) or cinnamyl alcohol dehydrogenase (CAD). Transgenic poplars with CAD or COMT antisense constructs showed growth similar to control trees. CAD down-regulated poplars displayed a red coloration mainly in the outer xylem. A 90% lower COMT activity did not change lignin content but dramatically increased the frequency of guaiacyl units and resistant biphenyl linkages in lignin. This alteration severely lowered the efficiency of kraft pulping. The Klason lignin level of CAD-transformed poplars was slightly lower than that of the control. Whereas CAD down-regulation did not change the frequency of labile ether bonds or guaiacyl units in lignin, it increased the proportion of syringaldehyde and diarylpropane structures and, more importantly with regard to kraft pulping, of free phenolic groups in lignin. In the most depressed line, ASCAD21, a substantially higher content in free phenolic units facilitated lignin solubilization and fragmentation during kraft pulping. These results point the way to genetic modification of lignin structure to improve wood quality for the pulp industry.