Topic
Monolignol
About: Monolignol is a research topic. Over the lifetime, 508 publications have been published within this topic receiving 30546 citations.
Papers published on a yearly basis
Papers
TL;DR: A recent challenge to the currently accepted theory of chemically controlled lignification, attempting to bring lignin into line with more organized biopolymers such as proteins, is logically inconsistent with the most basic details of the structure.
Abstract: Lignins are complex natural polymers resulting from oxidative coupling of, primarily, 4-hydroxyphenylpropanoids. An understanding of their nature is evolving as a result of detailed structural studies, recently aided by the availability of lignin-biosynthetic-pathway mutants and transgenics. The currently accepted theory is that the lignin polymer is formed by combinatorial-like phenolic coupling reactions, via radicals generated by peroxidase-H2O2, under simple chemical control where monolignols react endwise with the growing polymer. As a result, the actual structure of the lignin macromolecule is not absolutely defined or determined. The ``randomness'' of linkage generation (which is not truly statistically random but governed, as is any chemical reaction, by the supply of reactants, the matrix, etc.) and the astronomical number of possible isomers of even a simple polymer structure, suggest a low probability of two lignin macromolecules being identical. A recent challenge to the currently accepted theory of chemically controlled lignification, attempting to bring lignin into line with more organized biopolymers such as proteins, is logically inconsistent with the most basic details of lignin structure. Lignins may derive in part from monomers and conjugates other than the three primary monolignols (p-coumaryl, coniferyl, and sinapyl alcohols). The plasticity of the combinatorial polymerization reactions allows monomer substitution and significant variations in final structure which, in many cases, the plant appears to tolerate. As such, lignification is seen as a marvelously evolved process allowing plants considerable flexibility in dealing with various environmental stresses, and conferring on them a striking ability to remain viable even when humans or nature alter ``required'' lignin-biosynthetic-pathway genes/enzymes. The malleability offers significant opportunities to engineer the structures of lignins beyond the limits explored to date.
1,605 citations
TL;DR: Together, these data describe the full complement of monolignol biosynthesis genes in Arabidopsis, provide a unified nomenclature, and serve as a basis for further functional studies.
Abstract: Lignin, one of the most abundant terrestrial biopolymers, is indispensable for plant structure and defense. With the availability of the full genome sequence, large collections of insertion mutants, and functional genomics tools, Arabidopsis constitutes an excellent model system to profoundly unravel the monolignol biosynthetic pathway. In a genome-wide bioinformatics survey of the Arabidopsis genome, 34 candidate genes were annotated that encode genes homologous to the 10 presently known enzymes of the monolignol biosynthesis pathway, nine of which have not been described before. By combining evolutionary analysis of these 10 gene families with in silico promoter analysis and expression data (from a reverse transcription-polymerase chain reaction analysis on an extensive tissue panel, mining of expressed sequence tags from publicly available resources, and assembling expression data from literature), 12 genes could be pinpointed as the most likely candidates for a role in vascular lignification. Furthermore, a possible novel link was detected between the presence of the AC regulatory promoter element and the biosynthesis of G lignin during vascular development. Together, these data describe the full complement of monolignol biosynthesis genes in Arabidopsis, provide a unified nomenclature, and serve as a basis for further functional studies.
823 citations
TL;DR: A number of aspects regarding the origin and evolution of lignin biosynthesis during land plant evolution are discussed, including the establishment of its monomer biosynthetic scaffold, potential precursors to the lIGNin polymer, as well as the emergence of the polymerization machinery and regulatory system.
Abstract: Contents
Summary 273
I. Introduction 273
II. Emergence of the monolignol biosynthetic scaffold 274
III. Occurrence and elaboration of lignification in tracheophytes 280
IV. Concluding remarks 282
Acknowledgements 282
References 282
Summary
Lignin, a phenolic polymer derived mainly from hydroxycinnamyl alcohols, is ubiquitously present in tracheophytes. The development of lignin biosynthesis has been considered to be one of the key factors that allowed land plants to flourish in terrestrial ecosystems. Lignin provides structural rigidity for tracheophytes to stand upright, and strengthens the cell wall of their water-conducting tracheary elements to withstand the negative pressure generated during transpiration. In this review, we discuss a number of aspects regarding the origin and evolution of lignin biosynthesis during land plant evolution, including the establishment of its monomer biosynthetic scaffold, potential precursors to the lignin polymer, as well as the emergence of the polymerization machinery and regulatory system. The accumulated knowledge on the topic, as summarized here, provides us with an evolutionary view on how this complex metabolic system emerged and developed.
796 citations
TL;DR: In this article, the expression of a lignin biosynthetic pathway gene Pt4CL1 encoding 4-coumarate:coenzyme A ligase (4CL) has been downregulated by antisense inhibition.
Abstract: Because lignin limits the use of wood for fiber, chemical, and energy production, strategies for its downregulation are of considerable interest. We have produced transgenic aspen (Populus tremuloides Michx.) trees in which expression of a lignin biosynthetic pathway gene Pt4CL1 encoding 4-coumarate:coenzyme A ligase (4CL) has been downregulated by antisense inhibition. Trees with suppressed Pt4CL1 expression exhibited up to a 45% reduction of lignin, but this was compensated for by a 15% increase in cellulose. As a result, the total lignin-cellulose mass remained essentially unchanged. Leaf, root, and stem growth were substantially enhanced, and structural integrity was maintained both at the cellular and whole-plant levels in the transgenic lines. Our results indicate that lignin and cellulose deposition could be regulated in a compensatory fashion, which may contribute to metabolic flexibility and a growth advantage to sustain the long-term structural integrity of woody perennials.
789 citations
TL;DR: Examining lignins in different species reveals the extent to which evolution and natural variation have resulted in the incorporation of 'non-traditional' phenolic monomers, including phenolics from beyond the monolignol biosynthetic pathway.
730 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2025 | 9 |
| 2024 | 22 |
| 2023 | 17 |
| 2022 | 64 |
| 2021 | 30 |
| 2020 | 33 |