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Dixon RA, Dickinson AJ. A century of studying plant secondary metabolism-From "what?" to "where, how, and why?". PLANT PHYSIOLOGY 2024; 195:48-66. [PMID: 38163637 PMCID: PMC11060662 DOI: 10.1093/plphys/kiad596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Accepted: 08/15/2023] [Indexed: 01/03/2024]
Abstract
Over the past century, early advances in understanding the identity of the chemicals that collectively form a living plant have led scientists to deeper investigations exploring where these molecules localize, how they are made, and why they are synthesized in the first place. Many small molecules are specific to the plant kingdom and have been termed plant secondary metabolites, despite the fact that they can play primary and essential roles in plant structure, development, and response to the environment. The past 100 yr have witnessed elucidation of the structure, function, localization, and biosynthesis of selected plant secondary metabolites. Nevertheless, many mysteries remain about the vast diversity of chemicals produced by plants and their roles in plant biology. From early work characterizing unpurified plant extracts, to modern integration of 'omics technology to discover genes in metabolite biosynthesis and perception, research in plant (bio)chemistry has produced knowledge with substantial benefits for society, including human medicine and agricultural biotechnology. Here, we review the history of this work and offer suggestions for future areas of exploration. We also highlight some of the recently developed technologies that are leading to ongoing research advances.
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Affiliation(s)
- Richard A Dixon
- BioDiscovery Institute and Department of Biological Sciences, University of North Texas, Denton, TX 76203, USA
| | - Alexandra Jazz Dickinson
- Department of Cell and Developmental Biology, University of California at San Diego, La Jolla, CA 92093, USA
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Yoshioka K, Kim H, Lu F, De Ridder N, Vanholme R, Kajita S, Boerjan W, Ralph J. Hydroxycinnamaldehyde-derived benzofuran components in lignins. PLANT PHYSIOLOGY 2024; 194:1370-1382. [PMID: 37773018 DOI: 10.1093/plphys/kiad514] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 09/11/2023] [Accepted: 09/11/2023] [Indexed: 09/30/2023]
Abstract
Lignin is an abundant polymer in plant secondary cell walls. Prototypical lignins derive from the polymerization of monolignols (hydroxycinnamyl alcohols), mainly coniferyl and sinapyl alcohol, via combinatorial radical coupling reactions and primarily via the endwise coupling of a monomer with the phenolic end of the growing polymer. Hydroxycinnamaldehyde units have long been recognized as minor components of lignins. In plants deficient in cinnamyl alcohol dehydrogenase, the last enzyme in the monolignol biosynthesis pathway that reduces hydroxycinnamaldehydes to monolignols, chain-incorporated aldehyde unit levels are elevated. The nature and relative levels of aldehyde components in lignins can be determined from their distinct and dispersed correlations in 2D 1H-13C-correlated nuclear magnetic resonance (NMR) spectra. We recently became aware of aldehyde NMR peaks, well resolved from others, that had been overlooked. NMR of isolated low-molecular-weight oligomers from biomimetic radical coupling reactions involving coniferaldehyde revealed that the correlation peaks belonged to hydroxycinnamaldehyde-derived benzofuran moieties. Coniferaldehyde 8-5-coupling initially produces the expected phenylcoumaran structures, but the derived phenolic radicals undergo preferential disproportionation rather than radical coupling to extend the growing polymer. As a result, the hydroxycinnamaldehyde-derived phenylcoumaran units are difficult to detect in lignins, but the benzofurans are now readily observed by their distinct and dispersed correlations in the aldehyde region of NMR spectra from any lignin or monolignol dehydrogenation polymer. Hydroxycinnamaldehydes that are coupled to coniferaldehyde can be distinguished from those coupled with a generic guaiacyl end-unit. These benzofuran peaks may now be annotated and reported and their structural ramifications further studied.
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Affiliation(s)
- Koichi Yoshioka
- The US Department of Energy's Great Lakes Bioenergy Research Center, University of Wisconsin, Madison, WI 53726, USA
- The Wisconsin Energy Institute, University of Wisconsin, Madison, WI 53726, USA
| | - Hoon Kim
- The US Department of Energy's Great Lakes Bioenergy Research Center, University of Wisconsin, Madison, WI 53726, USA
- The Wisconsin Energy Institute, University of Wisconsin, Madison, WI 53726, USA
| | - Fachuang Lu
- The US Department of Energy's Great Lakes Bioenergy Research Center, University of Wisconsin, Madison, WI 53726, USA
- The Wisconsin Energy Institute, University of Wisconsin, Madison, WI 53726, USA
| | - Nette De Ridder
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, Ghent 9052, Belgium
- VIB Center for Plant Systems Biology, VIB, Technologiepark 71, Ghent 9052, Belgium
| | - Ruben Vanholme
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, Ghent 9052, Belgium
- VIB Center for Plant Systems Biology, VIB, Technologiepark 71, Ghent 9052, Belgium
| | - Shinya Kajita
- Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, Tokyo 184-8588, Japan
- Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Tokyo 184-8588, Japan
| | - Wout Boerjan
- Department of Plant Biotechnology and Bioinformatics, Ghent University, Technologiepark 71, Ghent 9052, Belgium
- VIB Center for Plant Systems Biology, VIB, Technologiepark 71, Ghent 9052, Belgium
| | - John Ralph
- The US Department of Energy's Great Lakes Bioenergy Research Center, University of Wisconsin, Madison, WI 53726, USA
- The Wisconsin Energy Institute, University of Wisconsin, Madison, WI 53726, USA
- Department of Biochemistry, University of Wisconsin, Madison, WI 53706, USA
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Rates ADB, Cesarino I. Pour some sugar on me: The diverse functions of phenylpropanoid glycosylation. JOURNAL OF PLANT PHYSIOLOGY 2023; 291:154138. [PMID: 38006622 DOI: 10.1016/j.jplph.2023.154138] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 11/06/2023] [Indexed: 11/27/2023]
Abstract
The phenylpropanoid metabolism is the source of a vast array of specialized metabolites that play diverse functions in plant growth and development and contribute to all aspects of plant interactions with their surrounding environment. These compounds protect plants from damaging ultraviolet radiation and reactive oxygen species, provide mechanical support for the plants to stand upright, and mediate plant-plant and plant-microorganism communications. The enormous metabolic diversity of phenylpropanoids is further expanded by chemical modifications known as "decorative reactions", including hydroxylation, methylation, glycosylation, and acylation. Among these modifications, glycosylation is the major driving force of phenylpropanoid structural diversification, also contributing to the expansion of their properties. Phenylpropanoid glycosylation is catalyzed by regioselective uridine diphosphate (UDP)-dependent glycosyltransferases (UGTs), whereas glycosyl hydrolases known as β-glucosidases are the major players in deglycosylation. In this article, we review how the glycosylation process affects key physicochemical properties of phenylpropanoids, such as molecular stability and solubility, as well as metabolite compartmentalization/storage and biological activity/toxicity. We also summarize the recent knowledge on the functional implications of glycosylation of different classes of phenylpropanoid compounds. A balance of glycosylation/deglycosylation might represent an essential molecular mechanism to regulate phenylpropanoid homeostasis, allowing plants to dynamically respond to diverse environmental signals.
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Affiliation(s)
- Arthur de Barros Rates
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão 277, 05508-090, São Paulo, Brazil
| | - Igor Cesarino
- Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo, Rua do Matão 277, 05508-090, São Paulo, Brazil; Synthetic and Systems Biology Center, InovaUSP, Avenida Professor Lucio Martins Rodrigues 370, 05508-020, São Paulo, Brazil.
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Muro-Villanueva F, Pysh LD, Kim H, Bouse T, Ralph J, Luo Z, Cooper BR, Jannasch AS, Zhang Z, Gu C, Chapple C. Pinoresinol rescues developmental phenotypes of Arabidopsis phenylpropanoid mutants overexpressing FERULATE 5-HYDROXYLASE. Proc Natl Acad Sci U S A 2023; 120:e2216543120. [PMID: 37487096 PMCID: PMC10401026 DOI: 10.1073/pnas.2216543120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 06/12/2023] [Indexed: 07/26/2023] Open
Abstract
Most phenylpropanoid pathway flux is directed toward the production of monolignols, but this pathway also generates multiple bioactive metabolites. The monolignols coniferyl and sinapyl alcohol polymerize to form guaiacyl (G) and syringyl (S) units in lignin, components that are characteristic of plant secondary cell walls. Lignin negatively impacts the saccharification potential of lignocellulosic biomass. Although manipulation of its content and composition through genetic engineering has reduced biomass recalcitrance, in some cases, these genetic manipulations lead to impaired growth. The reduced-growth phenotype is often attributed to poor water transport due to xylem collapse in low-lignin mutants, but alternative models suggest that it could be caused by the hyper- or hypoaccumulation of phenylpropanoid intermediates. In Arabidopsis thaliana, overexpression of FERULATE 5-HYDROXYLASE (F5H) shifts the normal G/S lignin ratio to nearly pure S lignin and does not result in substantial changes to plant growth. In contrast, when we overexpressed F5H in the low-lignin mutants cinnamyl dehydrogenase c and d (cadc cadd), cinnamoyl-CoA reductase 1, and reduced epidermal fluorescence 3, plant growth was severely compromised. In addition, cadc cadd plants overexpressing F5H exhibited defects in lateral root development. Exogenous coniferyl alcohol (CA) and its dimeric coupling product, pinoresinol, rescue these phenotypes. These data suggest that mutations in the phenylpropanoid pathway limit the biosynthesis of pinoresinol, and this effect is exacerbated by overexpression of F5H, which further draws down cellular pools of its precursor, CA. Overall, these genetic manipulations appear to restrict the synthesis of pinoresinol or a downstream metabolite that is necessary for plant growth.
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Affiliation(s)
- Fabiola Muro-Villanueva
- Department of Biochemistry, Purdue University, West Lafayette, IN47907
- Center for Plant Biology, Purdue University, West Lafayette, IN47907
| | | | - Hoon Kim
- US Department of Energy’s Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, Madison, WI53726
| | - Tyler Bouse
- Department of Biochemistry, Purdue University, West Lafayette, IN47907
| | - John Ralph
- US Department of Energy’s Great Lakes Bioenergy Research Center, Wisconsin Energy Institute, Madison, WI53726
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI53706
| | - Zhiwei Luo
- Department of Biochemistry, Purdue University, West Lafayette, IN47907
- Center for Plant Biology, Purdue University, West Lafayette, IN47907
| | - Bruce R. Cooper
- Bindley Bioscience Center, Purdue University, West Lafayette, IN47907
| | - Amber S. Jannasch
- Bindley Bioscience Center, Purdue University, West Lafayette, IN47907
| | - Zeyu Zhang
- Department of Statistics, Purdue University, West Lafayette, IN47907
| | - Chong Gu
- Department of Statistics, Purdue University, West Lafayette, IN47907
| | - Clint Chapple
- Department of Biochemistry, Purdue University, West Lafayette, IN47907
- Center for Plant Biology, Purdue University, West Lafayette, IN47907
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