Probing native lignin macromolecular configuration in Arabidopsis thaliana in specific cell wall types: Further insights into limited substrate degeneracy and assembly of the lignins of ref8, fah 1–2 and C4H::F5H lines

Abstract

The interest in renewable, plant-derived, bioenergy/biofuels has resulted in a renaissance of plant cell-wall/lignin research. Herein, effects of modulating lignin monomeric compositions in a single plant species, Arabidopsis, are described. The earliest stage of putative "AcBr/Klason lignin" deposition was apparently unaffected by modulating p-coumarate 3-hydroxylase or ferulate 5-hydroxylase activities. This finding helps account for the inability of many other studies to fully suppress the reported putative levels of lignin deposition through monolignol biosynthesis manipulation, and also underscores limitations in frequently used lignin analytical protocols. The overall putative lignin content was greatly reduced (circa 62%) in a plant line harboring an H-(p-hydroxyphenyl) enriched lignin phenotype. This slightly increased H-monomer deposition level apparently occurred in cell-wall domains normally harboring guaiacyl (G) and/or syringyl (S) lignin moieties. For G- and S-enriched lignin phenotypes, the overall lignification process appeared analogous to wild type, with only xylem fiber and interfascicular fiber cells forming the S-enriched lignins. Laser microscope dissection of vascular bundles and interfascicular fibers, followed by pyrolysis GC/MS, supported these findings. Some cell types, presumably metaxylem and possibly protoxylem, also afforded small amounts of benzodioxane (sub)structures due to limited substrate degeneracy (i.e. utilizing 5-hydroxyconiferyl alcohol rather than sinapyl alcohol). For all plant lines studied, the 8-O-4' inter-unit frequency of cleavable H, G and/or S monomers was essentially invariant of monomeric composition for a given (putative) lignin content. These data again underscore the need for determination of lignin primary structures and identification of all proteins/enzymes involved in control of lignin polymer assembly/macromolecular configuration.

Antisense Down-Regulation of 4CL Expression Alters Lignification, Tree Growth, and Saccharification Potential of Field-Grown Poplar

“…2L) that normally have a greater proportion of S monomers compared with the middle lamellae, cell corners, and vessel cell walls (Saka and Goring, 1985;Donaldson, 2001;Nakashima et al, 2008). Small but significant amounts of H-derived thioacidolysis monomeric units were observed in the brown wood transformants, in agreement with other data on mutant plants with significant reductions in lignin contents (Coleman et al, 2008;Patten et al, 2010a). Additionally, while the NBO data showed a similar trend in H units released (Fig.…”

“…To gain detailed insights into cell wall assembly, mutant or transgenic perturbations to lignin biosynthesis have been employed to alter native lignin content and monomer compositions (i.e. to shift ratios of syringyl [S], guaiacyl [G], and p-hydroxyphenyl [H] lignins; Porter et al, 1978;Miller et al, 1983;Baucher et al, 1996;Kajita et al, 1996;Lee et al, 1997;Anterola and Lewis, 2002;Davin et al, 2008aDavin et al, , 2008bPatten et al, 2010a). In addition, such perturbations give needed insight into the role of lignin in providing resistance to mechanical (Mark, 1967;Niklas, 1992;Gindl and Teischinger, 2002) and biotic (Dixon and Paiva, 1995) stresses.…”

Arogenate Dehydratase Isoenzymes Profoundly and Differentially Modulate Carbon Flux into Lignins

“…Histochemical Staining-Histochemical staining and imaging of fresh hand-cut sections taken near the base of 7-week-old stems (Stage 3) (25) of both mutants and WT lines were carried out as described previously by Patten et al (26). For detection of presumed guaiacyl (G) lignin, stem cross-sections were placed in a phloroglucinol-HCl (0.1%, w/v) solution for 30 min (27,28), transferred to a glass slide, and observed under the differential interference contrast setting using an Olympus System Microscope, Model BHT (Olympus Optical Co., Ltd., Tokyo, Japan).…”

“…Laser Microscope Dissection of Vascular Bundles and Interfascicular Regions-Laser microscope dissection was used to separate the vascular bundle (VB) and interfascicular fiber (IF) regions from 7-week-old stems (Stage 3) for WT and adt1/4/5 lines as described previously (26). Briefly, sections were made using a Cryocut 1800 microtome (Leica Microsystems) and laser-microdissected using a P.A.L.M.…”

4- O -methylation of glucuronic acid in Arabidopsis glucuronoxylan is catalyzed by a domain of unknown function family 579 protein

“…Patten et al (50) observed that the S-lignin is less abundant in Arabidopsis stem vascular bundles than in interfascicular fibers. Our data (Fig.…”