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| 2. |
- Ankele, Elisabeth, et al.
(författare)
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In vivo visualization of Mg-ProtoporphyrinIX, a coordinator of photosynthetic gene expression in the nucleus and the chloroplast
- 2007
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Ingår i: Plant Cell. - Rockville Pike, Bethesda MD, USA : National Center for Biotechnology Information, U.S. National Library of Medicine. - 1040-4651 .- 1532-298X. ; 19:6, s. 1964-1979
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Tidskriftsartikel (refereegranskat)abstract
- The photosynthetic apparatus is composed of proteins encoded by genes from both the nucleus and the chloroplast. To ensure that the photosynthetic complexes are assembled stoichiometrically and to enable their rapid reorganization in response to a changing environment, the plastids emit signals that regulate nuclear gene expression to match the status of the plastids. One of the plastid signals, the chlorophyll intermediate Mg-ProtoporphyrinIX (Mg-ProtoIX) accumulates under stress conditions and acts as a negative regulator of photosynthetic gene expression. By taking advantage of the photoreactive property of tetrapyrroles, Mg-ProtoIX could be visualized in the cells using confocal laser scanning spectroscopy. Our results demonstrate that Mg-ProtoIX accumulated both in the chloroplast and in the cytosol during stress conditions. Thus, the signaling metabolite is exported from the chloroplast, transmitting the plastid signal to the cytosol. Our results from the Mg-ProtoIX over- and underaccumulating mutants copper response defect and genome uncoupled5, respectively, demonstrate that the expression of both nuclear- and plastid-encoded photosynthesis genes is regulated by the accumulation of Mg-ProtoIX. Thus, stress-induced accumulation of the signaling metabolite Mg-ProtoIX coordinates nuclear and plastidic photosynthetic gene expression.
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| 3. |
- Barros, Jaime, et al.
(författare)
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The cell biology of lignification in higher plants
- 2015
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Ingår i: Annals of Botany. - : Oxford University Press (OUP). - 0305-7364 .- 1095-8290. ; 115:7, s. 1053-1074
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Forskningsöversikt (refereegranskat)abstract
- Background Lignin is a polyphenolic polymer that strengthens and waterproofs the cell wall of specialized plant cell types. Lignification is part of the normal differentiation programme and functioning of specific cell types, but can also be triggered as a response to various biotic and abiotic stresses in cells that would not otherwise be lignifying.Scope Cell wall lignification exhibits specific characteristics depending on the cell type being considered. These characteristics include the timing of lignification during cell differentiation, the palette of associated enzymes and substrates, the sub-cellular deposition sites, the monomeric composition and the cellular autonomy for lignin monomer production. This review provides an overview of the current understanding of lignin biosynthesis and polymerization at the cell biology level.Conclusions The lignification process ranges from full autonomy to complete co-operation depending on the cell type. The different roles of lignin for the function of each specific plant cell type are clearly illustrated by the multiple phenotypic defects exhibited by knock-out mutants in lignin synthesis, which may explain why no general mechanism for lignification has yet been defined. The range of phenotypic effects observed include altered xylem sap transport, loss of mechanical support, reduced seed protection and dispersion, and/or increased pest and disease susceptibility.
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| 4. |
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| 5. |
- Blaschek, Leonard, et al.
(författare)
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Cellular and Genetic Regulation of Coniferaldehyde Incorporation in Lignin of Herbaceous and Woody Plants by Quantitative Wiesner Staining
- 2020
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Ingår i: Frontiers in Plant Science. - : Frontiers Media S.A.. - 1664-462X. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Lignin accumulates in the cell walls of specialized cell types to enable plants to stand upright and conduct water and minerals, withstand abiotic stresses, and defend themselves against pathogens. These functions depend on specific lignin concentrations and subunit composition in different cell types and cell wall layers. However, the mechanisms controlling the accumulation of specific lignin subunits, such as coniferaldehyde, during the development of these different cell types are still poorly understood. We herein validated the Wiesner test (phloroglucinol/HCl) for the restrictive quantitative in situ analysis of coniferaldehyde incorporation in lignin. Using this optimized tool, we investigated the genetic control of coniferaldehyde incorporation in the different cell types of genetically-engineered herbaceous and woody plants with modified lignin content and/or composition. Our results demonstrate that the incorporation of coniferaldehyde in lignified cells is controlled by (a) autonomous biosynthetic routes for each cell type, combined with (b) distinct cell-to-cell cooperation between specific cell types, and (c) cell wall layer-specific accumulation capacity. This process tightly regulates coniferaldehyde residue accumulation in specific cell types to adapt their property and/or function to developmental and/or environmental changes.
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| 6. |
- Blaschek, Leonard, 1992-
(författare)
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Cellular Control and Physiological Importance of Vascular Lignification
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lignin is indispensable for vascular plants. It allows their cells to coalesce into gravity-defying giants, hardens them to withstand pressures and predators, and waterproofs them to allow the flow of water only where it is advantageous. Lignin fulfils these different functions as a structural component of specialised cell walls in a wide range of different tissues and cell types. Between them, lignin shows great heterogeneity in its concentration and composition. The biosynthesis of lignin proceeds via monomer biosynthesis in the cell, export of the monomers into the apoplast and oxidative polymerisation by laccases (LACs) and class III peroxidases (PRXs) in the cell wall. In this thesis, I investigated how these processes are regulated to allow distinct lignification programs in different cell types and even adjacent cell wall layers (I–III) and what physiological advantages these differences in lignin amount and composition confer to the plant (IV). In paper I and II, we optimised and validated the histochemical Wiesner test and Raman microspectroscopy for the in situ quantitative analysis of lignin. We then used those techniques to map the cell autonomous and cell–cell cooperative genetic programs that regulate lignin monomer biosynthesis in the vasculature of Arabidopsis thaliana and Populus. Because lignin monomers are mobile in the cell wall prior to polymerisation, the sophisticated, cell type-specific genetic regulation of lignin monomer biosynthesis alone cannot explain the lignin differences observed between adjacent cell wall layers. In paper III, we therefore characterised five LACs paralogs involved in lignification, showing that they fine-tuned lignification at the nanoscale through distinct patterns of activity and substrate specificity. But what is the advantage of such a complex, layered control of lignification? In paper IV we began to answer this question by showing that different cell types – and even the same cell type in different developmental contexts – relied on distinct lignin amounts and compositions to withstand the unique stresses they were exposed to. Altogether, the work presented herein highlights how finely lignification is controlled the on cellular and sub-cellular scale, and how this regulation allows plants to fully exploit the versatile functions of lignin.
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| 7. |
- Blaschek, Leonard
(författare)
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Cellular Lignin Distribution Patterns and their Physiological Relevance
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The diverse morphological shapes of plants are made possible by the structural rigidity provided by cell walls. In order to support vertical growth and long distance water transport, cell walls need to resist a variety of biological and physical stresses. Lignin, a cell wall polyphenolic unique to vascular plants, has long been considered to structurally support the cell walls of xylem vessels and other specialised cell types against these forces. Lignin is a complex polymer whose monomeric composition and biochemical properties vary widely between different species, tissues and cell types. However, the precise characterisation of this micro-scale variation poses considerable methodological hurdles. As a result, it has yet to be understood how differences in lignin composition contribute to the cell-type specific functions of the cell wall. In the works presented herein, we optimise and validate the Wiesner test and Raman microspectroscopy for the quantitative characterisation of lignin in situ and use these techniques to show how cell-type specific genetic regulation of lignification is crucial for cell wall function. Using synthetic lignin monomers and polymers, as well as genetically altered Arabidopsis and Populus plants in conjunction with biochemical lignin composition analyses, we establish the Wiesner test as a specific high-resolution method to quantify coniferaldehyde (I), and show that Raman microspectroscopy allows the relative quantification of total lignin, guaiacyl lignin subunits (G-units), coniferyl alcohol and syringyl lignin subunits (S-units) (II). We then use these methods to characterise cell-autonomous and cell-cell cooperative lignification patterns and show that cell walls of different vessel types depend on distinct amounts of lignin and specific G-units for structural reinforcement (III). S-unit incorporation into vessel lignin and increased adjacency to neighbouring vessels on the other hand compromise their resistance to collapse (III). Altogether, we provide evidence for a lignification process consisting of a fine scale, cell-type specific regulatory network of lignin biosynthesis, cell-to-cell cooperative monomer supply, and cell wall layer specific monomer incorporation. Crucially, it is this dynamic small-scale regulation that allows lignified plant cell walls to fulfil their cell-type specific functions.
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| 8. |
- Blaschek, Leonard, et al.
(författare)
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Determining the Genetic Regulation and Coordination of Lignification in Stem Tissues of Arabidopsis Using Semiquantitative Raman Microspectroscopy
- 2020
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Ingår i: ACS Sustainable Chemistry and Engineering. - : American Chemical Society (ACS). - 2168-0485. ; 8:12, s. 4900-4909
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Tidskriftsartikel (refereegranskat)abstract
- Lignin is a phenolic polymer accumulatig in the cell walls of specific plant cell types to confer unique properties such as hydrophobicity, mechanical strengthening, and resistance to degradation. Different cell types accumulate lignin with specific concentration and composition to support their specific roles in the different plant tissues. Yet the genetic mechanisms controlling lignin quantity and composition differently between the different lignified cell types and tissues still remain poorly understood. To investigate this tissue-specific genetic regulation, we validated both the target molecular structures as well as the linear semi-quantitative capacity of Raman microspectroscopy to characterize the total lignin amount, S/G ratio, and coniferyl alcohol content in situ directly in plant biopsies. Using the optimized method on stems of multiple lignin biosynthesis loss-of-function mutants revealed that the genetic regulation of lignin is tissue specific, with distinct genes establishing nonredundant check-points to trigger specific compensatory adjustments affecting either lignin composition and/or cell wall polymer concentrations.
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| 9. |
- Blaschek, Leonard, et al.
(författare)
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Different combinations of laccase paralogs nonredundantly control the amount and composition of lignin in specific cell types and cell wall layers in Arabidopsis
- 2023
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Ingår i: The Plant Cell. - : Oxford University Press (OUP). - 1040-4651 .- 1532-298X. ; 35:2, s. 889-909
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Tidskriftsartikel (refereegranskat)abstract
- Vascular plants reinforce the cell walls of the different xylem cell types with lignin phenolic polymers. Distinct lignin chemistries differ between each cell wall layer and each cell type to support their specific functions. Yet the mechanisms controlling the tight spatial localization of specific lignin chemistries remain unclear. Current hypotheses focus on control by monomer biosynthesis and/or export, while cell wall polymerization is viewed as random and nonlimiting. Here, we show that combinations of multiple individual laccases (LACs) are nonredundantly and specifically required to set the lignin chemistry in different cell types and their distinct cell wall layers. We dissected the roles of Arabidopsis thaliana LAC4, 5, 10, 12, and 17 by generating quadruple and quintuple loss-of-function mutants. Loss of these LACs in different combinations led to specific changes in lignin chemistry affecting both residue ring structures and/or aliphatic tails in specific cell types and cell wall layers. Moreover, we showed that LAC-mediated lignification has distinct functions in specific cell types, waterproofing fibers, and strengthening vessels. Altogether, we propose that the spatial control of lignin chemistry depends on different combinations of LACs with nonredundant activities immobilized in specific cell types and cell wall layers.
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| 10. |
- Blaschek, Leonard, et al.
(författare)
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Functional complexity on a cellular scale : why in situ analyses are indispensable for our understanding of lignified tissues
- 2024
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Ingår i: Journal of Agricultural and Food Chemistry. - : American Chemical Society (ACS). - 0021-8561 .- 1520-5118.
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Forskningsöversikt (refereegranskat)abstract
- Lignins are a key adaptation that enables vascular plants to thrive in terrestrial habitats. Lignin is heterogeneous, containing upward of 30 different monomers, and its function is multifarious: It provides structural support, predetermined breaking points, ultraviolet protection, diffusion barriers, pathogen resistance, and drought resilience. Recent studies, carefully characterizing lignin in situ, have started to identify specific lignin compositions and ultrastructures with distinct cellular functions, but our understanding remains fractional. We summarize recent works and highlight where further in situ lignin analysis could provide valuable insights into plant growth and adaptation. We also summarize strengths and weaknesses of lignin in situ analysis methods.
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