Lignin Biosynthesis and Structure

Genetic Determinants for Enzymatic Digestion of Lignocellulosic Biomass Are Independent of Those for Lignin Abundance in a Maize Recombinant Inbred Population

“…Despite the improvements in saccharification yield made possible by the alteration of lignin content and composition (Vanholme et al, 2010;Fu et al, 2011a), none of our QTL for lignin and 4-vinylphenol abundance that have multiple year support overlap those for saccharification yield. In contrast, all but one of our QTL for saccharification yield (QTL3) map to at least one of the chromosomal regions associated with proxies of lignin abundance identified in other studies of maize, such as Klason lignin determination (total insoluble lignin) and artificial ruminant digestibility assays (Supplemental Table S6; Barrière et al, 2010;Lorenz et al, 2010;Lorenzana et al, 2010;Thomas et al, 2010;Truntzler et al, 2010).…”

“…Lignin is a key determinant of the recalcitrance of the plant cell wall to enzymatic digestion of cellulose, xylans, and other noncellulosic glycans to monosaccharides (saccharification yield) that may be used for biofuels production (Chen and Dixon, 2007;Himmel et al, 2007;Novaes et al, 2010). The genes involved in lignin biosynthesis from Phe to hydroxycinnamates and monolignol substrates are known, and modulating enzyme activities in this pathway alters the abundance of these substrates and the composition of polymerized lignin in the cell wall and increases the yield of sugars by enzymatic digestion (Bonawitz and Chapple, 2010;Vanholme et al, 2010). Forward genetic screens have also led to the discovery of visual and lignin-related phenotypes, such as brown-midrib maize (Zea mays) and sorghum (Sorghum bicolor), which show improved digestion by ruminant animals and increased sugar yield by enzyme hydrolysis (Cherney et al, 1991;Marita et al, 2003;Vermerris et al, 2007).…”

Controls on Coarse Wood Decay in Temperate Tree Species: Birth of the LOGLIFE Experiment

“…For instance, lignin is generally more recalcitrant per unit mass for gymnosperms than for angiosperms ). Different types of lignin coexist even across closely related species or within the same species and individual plants (Vanholme et al 2010) and these different chemical types of lignin can lead to substantially different decomposition rates of litters (Talbot et al 2012). Wood density as such is not regarded as having direct influence on decomposition rates, but may have important indirect effects, e.g.…”

Tricin, a Flavonoid Monomer in Monocot Lignification

“…This initiation role helps resolve a long-standing dilemma that monocot lignin chains do not appear to be initiated by monolignol homodehydrodimerization as they are in dicots that have similar syringyl-guaiacyl compositions. The term flavonolignin is recommended for the racemic oligomers and polymers of monolignols that start from tricin (or incorporate other flavonoids) in the cell wall, in analogy with the existing term flavonolignan that is used for the lowmolecular mass compounds composed of flavonoid and lignan moieties.Lignin, a complex phenylpropanoid polymer in the plant cell wall, is predominantly deposited in the cell walls of secondary-thickened cells (Vanholme et al, 2010). It is synthesized via oxidative radical coupling reactions from three prototypical monolignols, p-coumaryl, coniferyl, and sinapyl alcohols, differentiated by their degree of methoxylation ortho to the phenolic hydroxyl group.…”

“…Lignin, a complex phenylpropanoid polymer in the plant cell wall, is predominantly deposited in the cell walls of secondary-thickened cells (Vanholme et al, 2010). It is synthesized via oxidative radical coupling reactions from three prototypical monolignols, p-coumaryl, coniferyl, and sinapyl alcohols, differentiated by their degree of methoxylation ortho to the phenolic hydroxyl group.…”