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Laplaud V, Muller E, Demidova N, Drevensek S, Boudaoud A. Assessing the hydromechanical control of plant growth. J R Soc Interface 2024; 21:20240008. [PMID: 38715319 PMCID: PMC11077010 DOI: 10.1098/rsif.2024.0008] [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: 01/05/2024] [Revised: 03/16/2024] [Accepted: 03/21/2024] [Indexed: 05/12/2024] Open
Abstract
Multicellular organisms grow and acquire their shapes through the differential expansion and deformation of their cells. Recent research has addressed the role of cell and tissue mechanical properties in these processes. In plants, it is believed that growth rate is a function of the mechanical stress exerted on the cell wall, the thin polymeric layer surrounding cells, involving an effective viscosity. Nevertheless, recent studies have questioned this view, suggesting that cell wall elasticity sets the growth rate or that uptake of water is limiting for plant growth. To assess these issues, we developed a microfluidic device to quantify the growth rates, elastic properties and hydraulic conductivity of individual Marchantia polymorpha plants in a controlled environment with a high throughput. We characterized the effect of osmotic treatment and abscisic acid on growth and hydromechanical properties. Overall, the instantaneous growth rate of individuals is correlated with both bulk elastic modulus and hydraulic conductivity. Our results are consistent with a framework in which the growth rate is determined primarily by the elasticity of the wall and its remodelling, and secondarily by hydraulic conductivity. Accordingly, the coupling between the chemistry of the cell wall and the hydromechanics of the cell appears as key to set growth patterns during morphogenesis.
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Affiliation(s)
- Valentin Laplaud
- LadHyX, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
| | - Elise Muller
- LadHyX, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
| | - Natalia Demidova
- LadHyX, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
- Department of Chemical and Physical Sciences, University of Toronto at Mississauga, Mississauga, Ontario, L5L1C6, Canada
| | - Stéphanie Drevensek
- LadHyX, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
| | - Arezki Boudaoud
- LadHyX, CNRS, Ecole polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
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2
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Domozych DS, Bagdan K. The cell biology of charophytes: Exploring the past and models for the future. PLANT PHYSIOLOGY 2022; 190:1588-1608. [PMID: 35993883 PMCID: PMC9614468 DOI: 10.1093/plphys/kiac390] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 07/26/2022] [Indexed: 06/15/2023]
Abstract
Charophytes (Streptophyta) represent a diverse assemblage of extant green algae that are the sister lineage to land plants. About 500-600+ million years ago, a charophyte progenitor successfully colonized land and subsequently gave rise to land plants. Charophytes have diverse but relatively simple body plans that make them highly attractive organisms for many areas of biological research. At the cellular level, many charophytes have been used for deciphering cytoskeletal networks and their dynamics, membrane trafficking, extracellular matrix secretion, and cell division mechanisms. Some charophytes live in challenging habitats and have become excellent models for elucidating the cellular and molecular effects of various abiotic stressors on plant cells. Recent sequencing of several charophyte genomes has also opened doors for the dissection of biosynthetic and signaling pathways. While we are only in an infancy stage of elucidating the cell biology of charophytes, the future application of novel analytical methodologies in charophyte studies that include a broader survey of inclusive taxa will enhance our understanding of plant evolution and cell dynamics.
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Affiliation(s)
| | - Kaylee Bagdan
- Department of Biology, Skidmore Microscopy Imaging Center, Skidmore College, Saratoga Springs, New York 12866, USA
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3
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Feedback linking cell envelope stiffness, curvature, and synthesis enables robust rod-shaped bacterial growth. Proc Natl Acad Sci U S A 2022; 119:e2200728119. [PMID: 36191183 PMCID: PMC9564212 DOI: 10.1073/pnas.2200728119] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bacterial growth is remarkably robust to environmental fluctuations, yet the mechanisms of growth-rate homeostasis are poorly understood. Here, we combine theory and experiment to infer mechanisms by which Escherichia coli adapts its growth rate in response to changes in osmolarity, a fundamental physicochemical property of the environment. The central tenet of our theoretical model is that cell-envelope expansion is only sensitive to local information, such as enzyme concentrations, cell-envelope curvature, and mechanical strain in the envelope. We constrained this model with quantitative measurements of the dynamics of E. coli elongation rate and cell width after hyperosmotic shock. Our analysis demonstrated that adaptive cell-envelope softening is a key process underlying growth-rate homeostasis. Furthermore, our model correctly predicted that softening does not occur above a critical hyperosmotic shock magnitude and precisely recapitulated the elongation-rate dynamics in response to shocks with magnitude larger than this threshold. Finally, we found that, to coordinately achieve growth-rate and cell-width homeostasis, cells employ direct feedback between cell-envelope curvature and envelope expansion. In sum, our analysis points to cellular mechanisms of bacterial growth-rate homeostasis and provides a practical theoretical framework for understanding this process.
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Sun J, Rutherford ST, Silhavy TJ, Huang KC. Physical properties of the bacterial outer membrane. Nat Rev Microbiol 2022; 20:236-248. [PMID: 34732874 PMCID: PMC8934262 DOI: 10.1038/s41579-021-00638-0] [Citation(s) in RCA: 83] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/14/2021] [Indexed: 11/09/2022]
Abstract
It has long been appreciated that the Gram-negative outer membrane acts as a permeability barrier, but recent studies have uncovered a more expansive and versatile role for the outer membrane in cellular physiology and viability. Owing to recent developments in microfluidics and microscopy, the structural, rheological and mechanical properties of the outer membrane are becoming apparent across multiple scales. In this Review, we discuss experimental and computational studies that have revealed key molecular factors and interactions that give rise to the spatial organization, limited diffusivity and stress-bearing capacity of the outer membrane. These physical properties suggest broad connections between cellular structure and physiology, and we explore future prospects for further elucidation of the implications of outer membrane construction for cellular fitness and survival.
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Affiliation(s)
- Jiawei Sun
- Department of Bioengineering, Stanford University, Stanford, CA 94305, USA
| | - Steven T. Rutherford
- Department of Infectious Diseases, Genentech Inc., South San Francisco, CA 94080, USA,To whom correspondence should be addressed: , ,
| | - Thomas J. Silhavy
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA,To whom correspondence should be addressed: , ,
| | - Kerwyn Casey Huang
- Department of Bioengineering, Stanford University, Stanford, CA, USA. .,Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA. .,Chan Zuckerberg Biohub, San Francisco, CA, USA.
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5
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Hilty J, Muller B, Pantin F, Leuzinger S. Plant growth: the What, the How, and the Why. THE NEW PHYTOLOGIST 2021; 232:25-41. [PMID: 34245021 DOI: 10.1111/nph.17610] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Accepted: 06/19/2021] [Indexed: 05/28/2023]
Abstract
Growth is a widely used term in plant science and ecology, but it can have different meanings depending on the context and the spatiotemporal scale of analysis. At the meristem level, growth is associated with the production of cells and initiation of new organs. At the organ or plant scale and over short time periods, growth is often used synonymously with tissue expansion, while over longer time periods the increase in biomass is a common metric. At even larger temporal and spatial scales, growth is mostly described as net primary production. Here, we first address the question 'what is growth?'. We propose a general framework to distinguish between the different facets of growth, and the corresponding physiological processes, environmental drivers and mathematical formalisms. Based on these different definitions, we then review how plant growth can be measured and analysed at different organisational, spatial and temporal scales. We conclude by discussing why gaining a better understanding of the different facets of plant growth is essential to disentangle genetic and environmental effects on the phenotype, and to uncover the causalities around source or sink limitations of plant growth.
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Affiliation(s)
- Jonas Hilty
- School of Science, Auckland University of Technology, 46 Wakefield Street, Auckland, 1142, New Zealand
| | - Bertrand Muller
- LEPSE, Univ Montpellier, INRAE, Institut Agro, Montpellier, 34000, France
| | - Florent Pantin
- LEPSE, Univ Montpellier, INRAE, Institut Agro, Montpellier, 34000, France
| | - Sebastian Leuzinger
- School of Science, Auckland University of Technology, 46 Wakefield Street, Auckland, 1142, New Zealand
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Robust surface-to-mass coupling and turgor-dependent cell width determine bacterial dry-mass density. Proc Natl Acad Sci U S A 2021; 118:2021416118. [PMID: 34341116 PMCID: PMC8364103 DOI: 10.1073/pnas.2021416118] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Intracellular biomass density is an important variable for cellular physiology. It defines the crowded state of the cytoplasm and thus influences macromolecular interactions and transport. To control density during growth, bacteria must expand their cell volumes in synchrony with biomass. The regulation of volume growth and biomass density remain fundamentally not understood—in bacteria or any other organism. Using advanced microscopy, we demonstrate that cells control dry-mass density indirectly through two independent processes. First, cells expand surface area, rather than volume, in proportion with biomass growth. Second, cell width is controlled independently, with an important influence of turgor pressure. Our findings overturn a long-standing paradigm of mass-density constancy in bacteria and reveal fundamental determinants of dry-mass density and shape. During growth, cells must expand their cell volumes in coordination with biomass to control the level of cytoplasmic macromolecular crowding. Dry-mass density, the average ratio of dry mass to volume, is roughly constant between different nutrient conditions in bacteria, but it remains unknown whether cells maintain dry-mass density constant at the single-cell level and during nonsteady conditions. Furthermore, the regulation of dry-mass density is fundamentally not understood in any organism. Using quantitative phase microscopy and an advanced image-analysis pipeline, we measured absolute single-cell mass and shape of the model organisms Escherichia coli and Caulobacter crescentus with improved precision and accuracy. We found that cells control dry-mass density indirectly by expanding their surface, rather than volume, in direct proportion to biomass growth—according to an empirical surface growth law. At the same time, cell width is controlled independently. Therefore, cellular dry-mass density varies systematically with cell shape, both during the cell cycle or after nutrient shifts, while the surface-to-mass ratio remains nearly constant on the generation time scale. Transient deviations from constancy during nutrient shifts can be reconciled with turgor-pressure variations and the resulting elastic changes in surface area. Finally, we find that plastic changes of cell width after nutrient shifts are likely driven by turgor variations, demonstrating an important regulatory role of mechanical forces for width regulation. In conclusion, turgor-dependent cell width and a slowly varying surface-to-mass coupling constant are the independent variables that determine dry-mass density.
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Xing K, Zhao M, Niinemets Ü, Niu S, Tian J, Jiang Y, Chen HYH, White PJ, Guo D, Ma Z. Relationships Between Leaf Carbon and Macronutrients Across Woody Species and Forest Ecosystems Highlight How Carbon Is Allocated to Leaf Structural Function. FRONTIERS IN PLANT SCIENCE 2021; 12:674932. [PMID: 34177992 PMCID: PMC8226226 DOI: 10.3389/fpls.2021.674932] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 05/07/2021] [Indexed: 06/01/2023]
Abstract
Stoichiometry of leaf macronutrients can provide insight into the tradeoffs between leaf structural and metabolic investments. Structural carbon (C) in cell walls is contained in lignin and polysaccharides (cellulose, hemicellulose, and pectins). Much of leaf calcium (Ca) and a fraction of magnesium (Mg) were further bounded with cell wall pectins. The macronutrients phosphorus (P), potassium (K), and nitrogen (N) are primarily involved in cell metabolic functions. There is limited information on the functional interrelations among leaf C and macronutrients, and the functional dimensions characterizing the leaf structural and metabolic tradeoffs are not widely appreciated. We investigated the relationships between leaf C and macronutrient (N, P, K, Ca, Mg) concentrations in two widespread broad-leaved deciduous woody species Quercus wutaishanica (90 individuals) and Betula platyphylla (47 individuals), and further tested the generality of the observed relationships in 222 woody eudicots from 15 forest ecosystems. In a subsample of 20 broad-leaved species, we also analyzed the relationships among C, Ca, lignin, and pectin concentrations in leaf cell walls. We found a significant leaf C-Ca tradeoff operating within and across species and across ecosystems. This basic relationship was explained by variations in the share of cell wall lignin and pectin investments at the cell scale. The C-Ca tradeoffs were mainly driven by soil pH and mean annual temperature and precipitation, suggesting that leaves were more economically built with less C and more Ca as soil pH increased and at lower temperature and lower precipitation. However, we did not detect consistent patterns among C-N, and C-Mg at different levels of biological organization, suggesting substantial plasticity in N and Mg distribution among cell organelles and cell protoplast and cell wall. We observed two major axes of macronutrient differentiation: the cell-wall structural axis consisting of protein-free C and Ca and the protoplasm metabolic axis consisting of P and K, underscoring the decoupling of structural and metabolic elements inherently linked with cell wall from protoplasm investment strategies. We conclude that the tradeoffs between leaf C and Ca highlight how carbon is allocated to leaf structural function and suggest that this might indicate biogeochemical niche differentiation of species.
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Affiliation(s)
- Kaixiong Xing
- Key Laboratory of Ecosystem Network Observation and Modeling, Center for Forest Ecosystem Studies and Qianyanzhou Ecological Station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
| | - Mingfei Zhao
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing, China
| | - Ülo Niinemets
- Institute of Agricultural and Environmental Sciences, Estonian University of Life Sciences, Tartu, Estonia
- Estonian Academy of Sciences, Tallinn, Estonia
| | - Shuli Niu
- Key Laboratory of Ecosystem Network Observation and Modeling, Center for Forest Ecosystem Studies and Qianyanzhou Ecological Station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
| | - Jing Tian
- Key Laboratory of Plant-Soil Interactions, Ministry of Education, College of Resources and Environmental Sciences, China Agricultural University, National Academy of Agriculture Green Development, Beijing, China
| | - Yuan Jiang
- State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing, China
| | - Han Y. H. Chen
- College of Natural Resources Management, Lakehead University, Thunder Bay, ON, Canada
- College of Geographical Sciences, Fujian Normal University, Fujian, China
| | - Philip J. White
- The James Hutton Institute, Dundee, United Kingdom
- Zoology Department, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Dali Guo
- Key Laboratory of Ecosystem Network Observation and Modeling, Center for Forest Ecosystem Studies and Qianyanzhou Ecological Station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
| | - Zeqing Ma
- Key Laboratory of Ecosystem Network Observation and Modeling, Center for Forest Ecosystem Studies and Qianyanzhou Ecological Station, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
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8
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Baca Cabrera JC, Hirl RT, Zhu J, Schäufele R, Schnyder H. Atmospheric CO 2 and VPD alter the diel oscillation of leaf elongation in perennial ryegrass: compensation of hydraulic limitation by stored-growth. THE NEW PHYTOLOGIST 2020; 227:1776-1789. [PMID: 32369620 DOI: 10.1111/nph.16639] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 04/26/2020] [Indexed: 06/11/2023]
Abstract
We explored the effects of atmospheric CO2 concentration (Ca ) and vapor pressure deficit (VPD) on putative mechanisms controlling leaf elongation in perennial ryegrass. Plants were grown in stands at a Ca of 200, 400 or 800 μmol mol-1 combined with high (1.17 kPa) or low (0.59 kPa) VPD during the 16 h-day in well-watered conditions with reduced nitrogen supply. We measured day : night-variation of leaf elongation rate (LERday : LERnight ), final leaf length and width, epidermal cell number and length, stomatal conductance, transpiration, leaf water potential and water-soluble carbohydrates and osmotic potential in the leaf growth-and-differentiation zone (LGDZ). Daily mean LER or morphometric parameters did not differ between treatments, but LERnight strongly exceeded LERday , particularly at low Ca and high VPD. Across treatments LERday was negatively related to transpiration (R2 = 0.75) and leaf water potential (R2 = 0.81), while LERnight was independent of leaf water potential or turgor. Enhancement of LERnight over LERday was proportional to the turgor-change between day and night (R2 = 0.93). LGDZ sugar concentration was high throughout diel cycles, providing no evidence of source limitation in any treatment. Our data indicate a mechanism of diel cycling between daytime hydraulic and night-time stored-growth controls of LER, buffering Ca and daytime VPD effects on leaf elongation.
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Affiliation(s)
- Juan C Baca Cabrera
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, Freising-Weihenstephan, 85354, Germany
| | - Regina T Hirl
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, Freising-Weihenstephan, 85354, Germany
| | - Jianjun Zhu
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, Freising-Weihenstephan, 85354, Germany
| | - Rudi Schäufele
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, Freising-Weihenstephan, 85354, Germany
| | - Hans Schnyder
- Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, Freising-Weihenstephan, 85354, Germany
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9
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Palacio-López K, Tinaz B, Holzinger A, Domozych DS. Arabinogalactan Proteins and the Extracellular Matrix of Charophytes: A Sticky Business. FRONTIERS IN PLANT SCIENCE 2019; 10:447. [PMID: 31031785 PMCID: PMC6474363 DOI: 10.3389/fpls.2019.00447] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Accepted: 03/25/2019] [Indexed: 05/20/2023]
Abstract
Charophytes represent the group of green algae whose ancestors invaded land and ultimately gave rise to land plants 450 million years ago. While Zygnematophyceae are believed to be the direct sister lineage to embryophytes, different members of this group (Penium, Spirogyra, Zygnema) and the advanced thallus forming Coleochaete as well as the sarcinoid basal streptophyte Chlorokybus were investigated concerning their vegetative extracellular matrix (ECM) properties. Many taxa exhibit adhesion phenomena that are critical for affixing to a substrate or keeping cells together in a thallus, however, there is a great variety in possible reactions to e.g., wounding. In this study an analysis of adhesion mechanisms revealed that arabinogalactan proteins (AGPs) are most likely key adhesion molecules. Through use of monoclonal antibodies (JIM13) or the Yariv reagent, AGPs were located in cell surface sheaths and cell walls that were parts of the adhesion focal zones on substrates including wound induced rhizoid formation. JIM5, detecting highly methyl-esterfied homoglacturonan and JIM8, an antibody detecting AGP glycan and LM6 detecting arabinans were also tested and a colocalization was found in several examples (e.g., Zygnema) suggesting an interplay between these components. AGPs have been described in this study to perform both, cell to cell adhesion in algae forming thalli and cell to surface adhesion in the filamentous forms. These findings enable a broader evolutionary understanding of the function of AGPs in charophyte green algae.
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Affiliation(s)
| | - Berke Tinaz
- Department of Biology, Skidmore College, Saratoga Springs, NY, United States
| | | | - David S. Domozych
- Department of Biology, Skidmore College, Saratoga Springs, NY, United States
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10
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Herburger K, Ryan LM, Popper ZA, Holzinger A. Localisation and substrate specificities of transglycanases in charophyte algae relate to development and morphology. J Cell Sci 2018; 131:jcs203208. [PMID: 28827406 PMCID: PMC5722204 DOI: 10.1242/jcs.203208] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 08/16/2017] [Indexed: 12/26/2022] Open
Abstract
Cell wall-modifying enzymes have been previously investigated in charophyte green algae (CGA) in cultures of uniform age, giving limited insight into their roles. Therefore, we investigated the in situ localisation and specificity of enzymes acting on hemicelluloses in CGA genera of different morphologies and developmental stages. In vivo transglycosylation between xyloglucan and an endogenous donor in filamentous Klebsormidium and Zygnema was observed in longitudinal cell walls of young (1 month) but not old cells (1 year), suggesting that it has a role in cell growth. By contrast, in parenchymatous Chara, transglycanase action occurred in all cell planes. In Klebsormidium and Zygnema, the location of enzyme action mainly occurred in regions where xyloglucans and mannans, and to a lesser extent mixed-linkage β-glucan (MLG), were present, indicating predominantly xyloglucan:xyloglucan endotransglucosylase (XET) activity. Novel transglycosylation activities between xyloglucan and xylan, and xyloglucan and galactomannan were identified in vitro in both genera. Our results show that several cell wall-modifying enzymes are present in CGA, and that differences in morphology and cell age are related to enzyme localisation and specificity. This indicates an evolutionary significance of cell wall modifications, as similar changes are known in their immediate descendants, the land plants. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Klaus Herburger
- Department of Botany, Functional Plant Biology, University of Innsbruck, Sternwartestraße 16, 6020 Innsbruck, Austria
| | - Louise M Ryan
- Botany and Plant Science and Ryan Institute for Environmental, Marine, and Energy Research, School of Natural Sciences, National University of Ireland, Galway, University Road, H91 TK33 Galway, Ireland
| | - Zoë A Popper
- Botany and Plant Science and Ryan Institute for Environmental, Marine, and Energy Research, School of Natural Sciences, National University of Ireland, Galway, University Road, H91 TK33 Galway, Ireland
| | - Andreas Holzinger
- Department of Botany, Functional Plant Biology, University of Innsbruck, Sternwartestraße 16, 6020 Innsbruck, Austria
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Galletti R, Verger S, Hamant O, Ingram GC. Developing a 'thick skin': a paradoxical role for mechanical tension in maintaining epidermal integrity? Development 2017; 143:3249-58. [PMID: 27624830 DOI: 10.1242/dev.132837] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Plant aerial epidermal tissues, like animal epithelia, act as load-bearing layers and hence play pivotal roles in development. The presence of tension in the epidermis has morphogenetic implications for organ shapes but it also constantly threatens the integrity of this tissue. Here, we explore the multi-scale relationship between tension and cell adhesion in the plant epidermis, and we examine how tensile stress perception may act as a regulatory input to preserve epidermal tissue integrity and thus normal morphogenesis. From this, we identify parallels between plant epidermal and animal epithelial tissues and highlight a list of unexplored questions for future research.
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Affiliation(s)
- Roberta Galletti
- Laboratoire Reproduction et Développement des Plantes, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, Lyon F-69342, France
| | - Stéphane Verger
- Laboratoire Reproduction et Développement des Plantes, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, Lyon F-69342, France
| | - Olivier Hamant
- Laboratoire Reproduction et Développement des Plantes, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, Lyon F-69342, France
| | - Gwyneth C Ingram
- Laboratoire Reproduction et Développement des Plantes, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, Lyon F-69342, France
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12
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Abstract
Although many molecular regulators of morphogenesis have been identified in plants, it remains largely unknown how the molecular networks influence local cell shape and how cell growth, form, and position are coordinated during tissue and organ formations. So far, analyses of gene function in morphogenesis have mainly focused on the qualitative analysis of phenotypes, often providing limited mechanistic insight into how particular factors act. For this reason, there has been a growing interest in mathematical and computational models to formalize and test hypotheses. These require much more rigorous, quantitative approaches; in parallel, new quantitative and correlative imaging pipelines have been developed to study morphogenesis. Here, we describe a number of such methods, focusing on live imaging.
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Affiliation(s)
- T Stanislas
- Laboratoire de Reproduction et Développement des Plantes, ENS-Lyon, INRA, CNRS, UCBL, Université de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France
| | - O Hamant
- Laboratoire de Reproduction et Développement des Plantes, ENS-Lyon, INRA, CNRS, UCBL, Université de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France
| | - J Traas
- Laboratoire de Reproduction et Développement des Plantes, ENS-Lyon, INRA, CNRS, UCBL, Université de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France
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13
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Pietruszka M, Haduch-Sendecka A. A quantitative report on the impact of chloride on the kinetic coefficients of auxin-induced growth: a numerical contribution to the "acid growth hypothesis". SPRINGERPLUS 2016; 5:1978. [PMID: 27933246 PMCID: PMC5108741 DOI: 10.1186/s40064-016-3626-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 11/01/2016] [Indexed: 11/23/2022]
Abstract
This work presents the application of several our own novel methods of analysing the kinetics of plant growth, which create, among others, a common platform for the comparison of experimental results. A relatively simple formula is used to parameterize the wide range of data that has been obtained for Zea mays L. in the literature, though it can also be used for different species. A biophysical/biochemical interpretation of the parameters was obtained from a theoretical model that is based on a modified Lockhart equation. The derived formula, which was extended for practical use in Zajdel et al. (Acta Physiol Plant 38:5, 2016), and which was implemented in the attached computer program (ibid.), allowed the data that was obtained from the growth-related problems to be parameterized in a simple way. As a working example that shows the robustness of our approach, we comment in detail on the qualitative assessments of the impact of chloride ions on auxin-induced growth. We note that calculated continuous curves (fits), which are rooted in the growth functional that was introduced by Pietruszka (J Theor Biol 315:119-127, 2012), were in a perfect agreement (R2 ~ 0.99998) with the raw experimental data that was published recently by Burdach et al. (Ann Bot 114:1023-1034, 2014). This fact justified the use of this strict technique, which allows for the determination of kinetic coefficients, to critically evaluate the results and suppositions (claims) therein. Moreover, we calculated the time-delay derivative of elongation growth-pH cross-correlations, and validated the "acid growth hypothesis" in figures by considering, amongst others, the magnitude of the H+-activity of elongation growth (per μm). An empirical constant (field strength), EH+ = Em/(log10 1/aH+ ∙ μm) = 0.157 ± 0.009 [V/mm] was obtained, where Em [mV] is the membrane potential in the perenchymal coleoptile cells of Zea mays L. When this relation is known, the membrane potential can not only be determined for intact growth, but also for different intervening substances exclusively from growth (or growth rate) and pH measurements, i.e. without performing electrophysiological measurements. However, the question of whether this constant is universal remains open.
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Affiliation(s)
- Mariusz Pietruszka
- Plant Physiology, Faculty of Biology and Environment Protection, University of Silesia, Katowice, Poland
| | - Aleksandra Haduch-Sendecka
- Plant Physiology, Faculty of Biology and Environment Protection, University of Silesia, Katowice, Poland
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Boyer JS. Enzyme-Less Growth in Chara and Terrestrial Plants. FRONTIERS IN PLANT SCIENCE 2016; 7:866. [PMID: 27446106 PMCID: PMC4914548 DOI: 10.3389/fpls.2016.00866] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Accepted: 06/02/2016] [Indexed: 05/21/2023]
Abstract
Enzyme-less chemistry appears to control the growth rate of the green alga Chara corallina. The chemistry occurs in the wall where a calcium pectate cycle determines both the rate of wall enlargement and the rate of pectate deposition into the wall. The process is the first to indicate that a wall polymer can control how a plant cell enlarges after exocytosis releases the polymer to the wall. This raises the question of whether other species use a similar mechanism. Chara is one of the closest relatives of the progenitors of terrestrial plants and during the course of evolution, new wall features evolved while pectate remained one of the most conserved components. In addition, charophytes contain auxin which affects Chara in ways resembling its action in terrestrial plants. Therefore, this review considers whether more recently acquired wall features require different mechanisms to explain cell expansion.
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Affiliation(s)
- John S. Boyer
- Division of Plant Sciences, College of Agriculture, Food and Natural Resources, University of Missouri, ColumbiaMO, USA
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15
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Domozych DS, Popper ZA, Sørensen I. Charophytes: Evolutionary Giants and Emerging Model Organisms. FRONTIERS IN PLANT SCIENCE 2016; 7:1470. [PMID: 27777578 PMCID: PMC5056234 DOI: 10.3389/fpls.2016.01470] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 09/15/2016] [Indexed: 05/20/2023]
Abstract
Charophytes are the group of green algae whose ancestral lineage gave rise to land plants in what resulted in a profoundly transformative event in the natural history of the planet. Extant charophytes exhibit many features that are similar to those found in land plants and their relatively simple phenotypes make them efficacious organisms for the study of many fundamental biological phenomena. Several taxa including Micrasterias, Penium, Chara, and Coleochaete are valuable model organisms for the study of cell biology, development, physiology and ecology of plants. New and rapidly expanding molecular studies are increasing the use of charophytes that in turn, will dramatically enhance our understanding of the evolution of plants and the adaptations that allowed for survival on land. The Frontiers in Plant Science series on "Charophytes" provides an assortment of new research reports and reviews on charophytes and their emerging significance as model plants.
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Affiliation(s)
- David S. Domozych
- Department of Biology, Skidmore College, Saratoga SpringsNY, USA
- *Correspondence: David S. Domozych,
| | - Zoë A. Popper
- Botany and Plant Science, School of Natural Science, National University of IrelandGalway, Ireland
| | - Iben Sørensen
- Plant Biology Section, School of Integrative Plant Science, Cornell University, IthacaNY, USA
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16
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Jensen OE, Fozard JA. Multiscale models in the biomechanics of plant growth. Physiology (Bethesda) 2015; 30:159-66. [PMID: 25729061 DOI: 10.1152/physiol.00030.2014] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Plant growth occurs through the coordinated expansion of tightly adherent cells, driven by regulated softening of cell walls. It is an intrinsically multiscale process, with the integrated properties of multiple cell walls shaping the whole tissue. Multiscale models encode physical relationships to bring new understanding to plant physiology and development.
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Affiliation(s)
- Oliver E Jensen
- School of Mathematics, University of Manchester, Manchester, United Kingdom; and
| | - John A Fozard
- Centre for Plant Integrative Biology, School of Biosciences, University of Nottingham, Sutton Bonington, United Kingdom
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17
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18
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Barbacci A, Magnenet V, Lahaye M. Thermodynamical journey in plant biology. FRONTIERS IN PLANT SCIENCE 2015; 6:481. [PMID: 26175747 PMCID: PMC4485339 DOI: 10.3389/fpls.2015.00481] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 06/15/2015] [Indexed: 05/04/2023]
Abstract
Nonequilibrium irreversible thermodynamics constitute a meaningful point of view suitable to explore life with a rich paradigm. This analytical framework can be used to span the gap from molecular processes to plant function and shows great promise to create a holistic description of life. Since living organisms dissipate energy, exchange entropy and matter with their environment, they can be assimilated to dissipative structures. This concept inherited from nonequilibrium thermodynamics has four properties which defines a scale independent framework suitable to provide a simpler and more comprehensive view of the highly complex plant biology. According to this approach, a biological function is modeled as a cascade of dissipative structures. Each dissipative structure, corresponds to a biological process, which is initiated by the amplification of a fluctuation. Evolution of the process leads to the breakage of the system symmetry and to the export of entropy. Exporting entropy to the surrounding environment corresponds to collecting information about it. Biological actors which break the symmetry of the system and which store information are by consequence, key actors on which experiments and data analysis focus most. This paper aims at illustrating properties of dissipative structure through familiar examples and thus initiating the dialogue between nonequilibrium thermodynamics and plant biology.
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Affiliation(s)
- Adelin Barbacci
- Biopolymers Interactions Assembly, Institut National de la Recherche Agronomique, UR 1268Nantes, France
- Laboratoire des Interactions Plantes Microorganismes, Institut National de la Recherche Agronomique, UMR441Castanet-Tolosan, France
- Laboratoire des Interactions Plantes Microorganismes, Centre Nationale de la Recherche Scientifique, UMR2594Castanet-Tolosan, France
- *Correspondence: Adelin Barbacci, Biopolymers Interactions Assembly, Institut National de la Recherche Agronomique, UR 1268, Rue de la Géraudiére, F-44316 Nantes, France ;
| | - Vincent Magnenet
- Laboratoire des Sciences de l'Ingénieur, de l'Informatique et de l'Imagerie (ICube), Université de Strasbourg, UMR Centre National de la Recherche Scientifique 7357Illkirch, France
| | - Marc Lahaye
- Biopolymers Interactions Assembly, Institut National de la Recherche Agronomique, UR 1268Nantes, France
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Penium margaritaceum: A Unicellular Model Organism for Studying Plant Cell Wall Architecture and Dynamics. PLANTS 2014; 3:543-58. [PMID: 27135519 PMCID: PMC4844280 DOI: 10.3390/plants3040543] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 10/16/2014] [Accepted: 11/06/2014] [Indexed: 11/17/2022]
Abstract
Penium margaritaceum is a new and valuable unicellular model organism for studying plant cell wall structure and developmental dynamics. This charophyte has a cell wall composition remarkably similar to the primary cell wall of many higher plants and clearly-defined inclusive zones containing specific polymers. Penium has a simple cylindrical phenotype with a distinct region of focused wall synthesis. Specific polymers, particularly pectins, can be identified using monoclonal antibodies raised against polymers of higher plant cell walls. Immunofluorescence-based labeling is easily performed using live cells that subsequently can be returned to culture and monitored. This feature allows for rapid assessment of wall expansion rates and identification of multiple polymer types in the wall microarchitecture during the cell cycle. Cryofixation by means of spray freezing provides excellent transmission electron microscopy imaging of the cell, including its elaborate endomembrane and cytoskeletal systems, both integral to cell wall development. Penium’s fast growth rate allows for convenient microarray screening of various agents that alter wall biosynthesis and metabolism. Finally, recent successful development of transformed cell lines has allowed for non-invasive imaging of proteins in cells and for RNAi reverse genetics that can be used for cell wall biosynthesis studies.
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20
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Domozych DS, Domozych CE. Multicellularity in green algae: upsizing in a walled complex. FRONTIERS IN PLANT SCIENCE 2014; 5:649. [PMID: 25477895 PMCID: PMC4235416 DOI: 10.3389/fpls.2014.00649] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 09/03/2014] [Indexed: 05/09/2023]
Abstract
Modern green algae constitute a large and diverse taxonomic assemblage that encompasses many multicellular phenotypes including colonial, filamentous, and parenchymatous forms. In all multicellular green algae, each cell is surrounded by an extracellular matrix (ECM), most often in the form of a cell wall. Volvocalean taxa like Volvox have an elaborate, gel-like, hydroxyproline rich glycoprotein covering that contains the cells of the colony. In "ulvophytes," uronic acid-rich and sulfated polysaccharides are the likely adhesion agents that maintain the multicellular habit. Charophytes also produce polysaccharide-rich cell walls and in late divergent taxa, pectin plays a critical role in cell adhesion in the multicellular complex. Cell walls are products of coordinated interaction of membrane trafficking, cytoskeletal dynamics and the cell's signal transduction machinery responding both to precise internal clocks and external environmental cues. Most often, these activities must be synchronized with the secretion, deposition and remodeling of the polymers of the ECM. Rapid advances in molecular genetics, cell biology and cell wall biochemistry of green algae will soon provide new insights into the evolution and subcellular processes leading to multicellularity.
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Affiliation(s)
- David S. Domozych
- Skidmore Microscopy Imaging Center, Department of Biology, Skidmore College, Saratoga SpringsNY, USA
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21
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Haduch-Sendecka A, Pietruszka M, Zajdel P. Power spectrum, growth velocities and cross-correlations of longitudinal and transverse oscillations of individual Nicotiana tabacum pollen tube. PLANTA 2014; 240:263-76. [PMID: 24817588 PMCID: PMC4107278 DOI: 10.1007/s00425-014-2083-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 04/17/2014] [Indexed: 05/25/2023]
Abstract
We report on our results concerning growth rate and oscillation modes of the individual pollen tube apex. The observed volumetric growth and growth rate periodicity in the longitudinal (axial) direction are accompanied by transverse oscillations with similar frequencies but higher energies than the axial modes. Examination of the time-domain coherence between oscillations in mutually perpendicular directions revealed minimal energy dissipation in the unperturbed (isotonic) case, opposite to the two remaining cases (hypertonic, hypotonic) with notable correlations. We conjecture that the minimal energy loss is therefore optimal in the natural growth conditions. The longitudinal growth velocity is also found to be the fastest in the unperturbed case. As a result, the isolated system (pollen tube tip) is conserving energy by transforming it from elastic potential energy of extending apical wall to the kinetic energy of periodical motion. The energy dissipation is found to be about 20 % smaller in axial direction than in lateral one, indicating that the main energy consumption is dedicated to the elongation. We further observe that the hypertonic spectrum is shifted towards lower and the hypotonic towards higher frequencies with respect to the isotonic spectrum. In consequence, the turgor pressure inside the growing cell influences monotonically the frequency of both modes of oscillations. The calculated power spectrum seen as a measure of the overall energy efficiency of tip growth under hypertonic, hypotonic and isotonic conditions implies that the biochemistry has been fine tuned to be optimal under normal growth conditions, which is the developmental implication of this work. A simple theoretical extension of the Ortega equation is derived and analysed with respect to its contribution to power spectrum. We show that the plastic term, related to the effective turgor pressure, with maximum contribution at frequency f = 0 is responsible for the steady growth. In turn, the elastic contribution dependent on the time derivative of pressure fluctuations tends to move the system into oscillatory mode (f > 0). None of those mechanisms is privileged over another. The coupling mechanism is naturally generated through a convolution of those two terms and will decide about the overall character of the growth for each particular case.
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Affiliation(s)
- Aleksandra Haduch-Sendecka
- Laboratory of Plant Physiology, Faculty of Biology and Environment Protection, University of Silesia, ul. Jagiellońska 28, 40032 Katowice, Poland
| | - Mariusz Pietruszka
- Laboratory of Plant Physiology, Faculty of Biology and Environment Protection, University of Silesia, ul. Jagiellońska 28, 40032 Katowice, Poland
| | - Paweł Zajdel
- Institute of Physics, University of Silesia, ul. Uniwersytecka 4, 40007 Katowice, Poland
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22
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Abstract
It has long been proposed that turgor pressure plays an essential role during bacterial growth by driving mechanical expansion of the cell wall. This hypothesis is based on analogy to plant cells, for which this mechanism has been established, and on experiments in which the growth rate of bacterial cultures was observed to decrease as the osmolarity of the growth medium was increased. To distinguish the effect of turgor pressure from pressure-independent effects that osmolarity might have on cell growth, we monitored the elongation of single Escherichia coli cells while rapidly changing the osmolarity of their media. By plasmolyzing cells, we found that cell-wall elastic strain did not scale with growth rate, suggesting that pressure does not drive cell-wall expansion. Furthermore, in response to hyper- and hypoosmotic shock, E. coli cells resumed their preshock growth rate and relaxed to their steady-state rate after several minutes, demonstrating that osmolarity modulates growth rate slowly, independently of pressure. Oscillatory hyperosmotic shock revealed that although plasmolysis slowed cell elongation, the cells nevertheless "stored" growth such that once turgor was reestablished the cells elongated to the length that they would have attained had they never been plasmolyzed. Finally, MreB dynamics were unaffected by osmotic shock. These results reveal the simple nature of E. coli cell-wall expansion: that the rate of expansion is determined by the rate of peptidoglycan insertion and insertion is not directly dependent on turgor pressure, but that pressure does play a basic role whereby it enables full extension of recently inserted peptidoglycan.
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Barbacci A, Lahaye M, Magnenet V. Another brick in the cell wall: biosynthesis dependent growth model. PLoS One 2013; 8:e74400. [PMID: 24066142 PMCID: PMC3774806 DOI: 10.1371/journal.pone.0074400] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Accepted: 08/01/2013] [Indexed: 11/19/2022] Open
Abstract
Expansive growth of plant cell is conditioned by the cell wall ability to extend irreversibly. This process is possible if (i) a tensile stress is developed in the cell wall due to the coupling effect between turgor pressure and the modulation of its mechanical properties through enzymatic and physicochemical reactions and if (ii) new cell wall elements can be synthesized and assembled to the existing wall. In other words, expansive growth is the result of coupling effects between mechanical, thermal and chemical energy. To have a better understanding of this process, models must describe the interplay between physical or mechanical variable with biological events. In this paper we propose a general unified and theoretical framework to model growth in function of energy forms and their coupling. This framework is based on irreversible thermodynamics. It is then applied to model growth of the internodal cell of Chara corallina modulated by changes in pressure and temperature. The results describe accurately cell growth in term of length increment but also in term of cell pectate biosynthesis and incorporation to the expanding wall. Moreover, the classical growth model based on Lockhart's equation such as the one proposed by Ortega, appears as a particular and restrictive case of the more general growth equation developed in this paper.
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Affiliation(s)
- Adelin Barbacci
- Biopolymers Interactions Assembly UR 1268 (BIA), Institut National de la Recherche Agronomique (INRA), Nantes, France
- * E-mail: (AB); (VM)
| | - Marc Lahaye
- Biopolymers Interactions Assembly UR 1268 (BIA), Institut National de la Recherche Agronomique (INRA), Nantes, France
| | - Vincent Magnenet
- Laboratoire des sciences de l'ingnieur, de l'informatique et de l'imagerie (ICube), Université de Strasbourg, UMR CNRS 7357, Illkirch, France
- * E-mail: (AB); (VM)
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25
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Kroeger J, Geitmann A. The pollen tube paradigm revisited. CURRENT OPINION IN PLANT BIOLOGY 2012; 15:618-24. [PMID: 23000432 DOI: 10.1016/j.pbi.2012.09.007] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 08/31/2012] [Accepted: 09/03/2012] [Indexed: 05/10/2023]
Abstract
The polar growth process characterizing pollen tube elongation has attracted numerous modeling attempts over the past years. While initial models focused on recreating the correct cellular geometry, recent models are increasingly based on experimentally assessed cellular parameters such as the dynamics of signaling processes and the mechanical properties of the cell wall. Recent modeling attempts have therefore substantially gained in biological relevance and predictive power. Different modeling methods are explained and the power and limitations of individual models are compared. Focus is on several recent models that use closed feedback loops in order to generate limit cycles representing the oscillatory behavior observed in growing tubes.
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26
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Pantin F, Simonneau T, Muller B. Coming of leaf age: control of growth by hydraulics and metabolics during leaf ontogeny. THE NEW PHYTOLOGIST 2012; 196:349-366. [PMID: 22924516 DOI: 10.1111/j.1469-8137.2012.04273.x] [Citation(s) in RCA: 137] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Accepted: 07/09/2012] [Indexed: 05/21/2023]
Abstract
Leaf growth is the central process facilitating energy capture and plant performance. This is also one of the most sensitive processes to a wide range of abiotic stresses. Because hydraulics and metabolics are two major determinants of expansive growth (volumetric increase) and structural growth (dry matter increase), we review the interaction nodes between water and carbon. We detail the crosstalks between water and carbon transports, including the dual role of stomata and aquaporins in regulating water and carbon fluxes, the coupling between phloem and xylem, the interactions between leaf water relations and photosynthetic capacity, the links between Lockhart's hydromechanical model and carbon metabolism, and the central regulatory role of abscisic acid. Then, we argue that during leaf ontogeny, these interactions change dramatically because of uncoupled modifications between several anatomical and physiological features of the leaf. We conclude that the control of leaf growth switches from a metabolic to a hydromechanical limitation during the course of leaf ontogeny. Finally, we illustrate how taking leaf ontogeny into account provides insights into the mechanisms underlying leaf growth responses to abiotic stresses that affect water and carbon relations, such as elevated CO2, low light, high temperature and drought.
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Affiliation(s)
- Florent Pantin
- INRA, UMR759, Laboratoire d'Ecophysiologie des Plantes sous Stress Environnementaux, 34060, Montpellier, France
| | - Thierry Simonneau
- INRA, UMR759, Laboratoire d'Ecophysiologie des Plantes sous Stress Environnementaux, 34060, Montpellier, France
| | - Bertrand Muller
- INRA, UMR759, Laboratoire d'Ecophysiologie des Plantes sous Stress Environnementaux, 34060, Montpellier, France
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27
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Wolf S, Mravec J, Greiner S, Mouille G, Höfte H. Plant cell wall homeostasis is mediated by brassinosteroid feedback signaling. Curr Biol 2012; 22:1732-7. [PMID: 22885061 DOI: 10.1016/j.cub.2012.07.036] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2012] [Revised: 06/25/2012] [Accepted: 07/11/2012] [Indexed: 10/28/2022]
Abstract
Brassinosteroid (BR) signaling is required for normal plant growth as shown by the dwarf phenotype of loss-of-function BR biosynthetic or perception mutants. Despite a detailed understanding of the BR signaling network, it is not clear how exactly BRs control growth. For instance, genetic sector analysis shows that BRs, in contrast to most other growth regulators, act locally, presumably in an autocrine and/or paracrine mode, suggesting that they have some role in feedback regulation. Here, we show that at least one role for BRs in growth control is to ensure pectin-dependent cell wall homeostasis. Pectins are complex block cell wall polymers, which can be modified in the wall by the enzyme pectin methylesterase (PME). Genetic or pharmacological interference with PME activity causes dramatic changes in growth behavior, which are primarily the result of the activation of the BR signaling pathway. We propose that this activation of BR signaling is part of a compensatory response, which protects the plant against the loss of cell wall integrity caused by the imbalance in pectin modification. Thus, feedback signaling from the cell wall is integrated by the BR signaling module to ensure homeostasis of cell wall biosynthesis and remodeling.
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Affiliation(s)
- Sebastian Wolf
- Institut Jean-Pierre Bourgin, UMR1318 INRA-AgroParisTech, Saclay Plant Science, 78026 Versailles, France
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28
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Proseus TE, Boyer JS. Calcium deprivation disrupts enlargement of Chara corallina cells: further evidence for the calcium pectate cycle. JOURNAL OF EXPERIMENTAL BOTANY 2012; 63:3953-8. [PMID: 22442410 PMCID: PMC3388837 DOI: 10.1093/jxb/ers089] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2011] [Revised: 02/06/2012] [Accepted: 02/27/2012] [Indexed: 05/20/2023]
Abstract
Pectin is a normal constituent of cell walls of green plants. When supplied externally to live cells or walls isolated from the large-celled green alga Chara corallina, pectin removes calcium from load-bearing cross-links in the wall, loosening the structure and allowing it to deform more rapidly under the action of turgor pressure. New Ca(2+) enters the vacated positions in the wall and the externally supplied pectin binds to the wall, depositing new wall material that strengthens the wall. A calcium pectate cycle has been proposed for these sub-reactions. In the present work, the cycle was tested in C. corallina by depriving the wall of external Ca(2+) while allowing the cycle to run. The prediction is that growth would eventually be disrupted by a lack of adequate deposition of new wall. The test involved adding pectate or the calcium chelator EGTA to the Ca(2+)-containing culture medium to bind the calcium while the cycle ran in live cells. After growth accelerated, turgor and growth eventually decreased, followed by an abrupt turgor loss and growth cessation. The same experiment with isolated walls suggested the walls of live cells became unable to support the plasma membrane. If instead the pectate or EGTA was replaced with fresh Ca(2+)-containing culture medium during the initial acceleration in live cells, growth was not disrupted and returned to the original rates. The operation of the cycle was thus confirmed, providing further evidence that growth rates and wall biosynthesis are controlled by these sub-reactions in plant cell walls.
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Affiliation(s)
| | - John S. Boyer
- College of Earth, Ocean and Environment (formerly Marine Studies), University of Delaware, Lewes, DE 19958, USA
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29
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Rojas ER, Hotton S, Dumais J. Chemically mediated mechanical expansion of the pollen tube cell wall. Biophys J 2012; 101:1844-53. [PMID: 22004737 DOI: 10.1016/j.bpj.2011.08.016] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 07/17/2011] [Accepted: 08/02/2011] [Indexed: 12/20/2022] Open
Abstract
Morphogenesis of plant cells is tantamount to the shaping of the stiff cell wall that surrounds them. To this end, these cells integrate two concomitant processes: 1), deposition of new material into the existing wall, and 2), mechanical deformation of this material by the turgor pressure. However, due to uncertainty regarding the mechanisms that coordinate these processes, existing models typically adopt a limiting case in which either one or the other dictates morphogenesis. In this report, we formulate a simple mechanism in pollen tubes by which deposition causes turnover of cell wall cross-links, thereby facilitating mechanical deformation. Accordingly, deposition and mechanics are coupled and are both integral aspects of the morphogenetic process. Among the key experimental qualifications of this model are: its ability to precisely reproduce the morphologies of pollen tubes; its prediction of the growth oscillations exhibited by rapidly growing pollen tubes; and its prediction of the observed phase relationships between variables such as wall thickness, cell morphology, and growth rate within oscillatory cells. In short, the model captures the rich phenomenology of pollen tube morphogenesis and has implications for other plant cell types.
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Affiliation(s)
- Enrique R Rojas
- Department of Physics, Harvard University, Cambridge, Massachusetts, USA.
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30
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Plavcová L, Hacke UG. Heterogeneous distribution of pectin epitopes and calcium in different pit types of four angiosperm species. THE NEW PHYTOLOGIST 2011; 192:885-897. [PMID: 21801182 DOI: 10.1111/j.1469-8137.2011.03842.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Intervessel pits act as safety valves that prevent the spread of xylem embolism. Pectin-calcium crosslinks within the pit membrane have been proposed to affect xylem vulnerability to cavitation. However, as the chemical composition of pit membranes is poorly understood, this hypothesis has not been verified. Using electron microscopy, immunolabeling, an antimonate precipitation technique, and ruthenium red staining, we studied the distribution of selected polysaccharides and calcium in the pit membranes of four angiosperm tree species. We tested whether shifts in xylem vulnerability resulting from perfusion of stems with a calcium chelating agent corresponded with the distribution of pectic homogalacturonans (HG) and/or calcium within interconduit pit membranes. No HG were detected in the main part of intervessel pit membranes, but were consistently found in the marginal membrane region known as the annulus. Calcium colocalized with HG in the annulus. In contrast to intervessel pits, the membrane of vessel-ray pits showed a high pectin content. The presence of two distinct chemical domains, the annulus and the actual pit membrane, can have substantial implications for pit membrane functioning. We propose that the annulus could affect the observed shift in xylem vulnerability after calcium removal by allowing increased pit membrane deflection.
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Affiliation(s)
- Lenka Plavcová
- Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, AB, Canada, T6G 2E3
| | - Uwe G Hacke
- Department of Renewable Resources, University of Alberta, 442 Earth Sciences Building, Edmonton, AB, Canada, T6G 2E3
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31
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Lew RR. How does a hypha grow? The biophysics of pressurized growth in fungi. Nat Rev Microbiol 2011; 9:509-18. [DOI: 10.1038/nrmicro2591] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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33
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Burr SJ, Fry SC. Feruloylated arabinoxylans are oxidatively cross-linked by extracellular maize peroxidase but not by horseradish peroxidase. MOLECULAR PLANT 2009; 2:883-92. [PMID: 19825665 DOI: 10.1093/mp/ssp044] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Covalent cross-linking of soluble extracellular arabinoxylans in living maize cultures, which models the cross-linking of wall-bound arabinoxylans, is due to oxidation of feruloyl esters to oligoferuloyl esters and ethers. The oxidizing system responsible could be H2O2/peroxidase, O2/laccase, or reactive oxygen species acting non-enzymically. To distinguish these possibilities, we studied arabinoxylan cross-linking in vivo and in vitro. In living cultures, exogenous, soluble, extracellular, feruloylated [pentosyl-3H]arabinoxylans underwent cross-linking, beginning abruptly 8 d after sub-culture. Cross-linking was suppressed by iodide, an H2O2 scavenger, indicating dependence on endogenous H2O2. However, exogenous H2O2 did not cause precocious cross-linking, despite the constant presence of endogenous peroxidases, suggesting that younger cultures contained natural cross-linking inhibitors. Dialysed culture-filtrates cross-linked [3H]arabinoxylans in vitro only if H2O2 was also added, indicating a peroxidase requirement. This cross-linking was highly ionic-strength-dependent. The peroxidases responsible were heat-labile, although relatively heat-stable peroxidases (assayed on o-dianisidine) were also present. Surprisingly, added horseradish peroxidase, even after heat-denaturation, blocked the arabinoxylan-cross-linking action of maize peroxidases, suggesting that the horseradish protein was a competing substrate for [3H]arabinoxylan coupling. In conclusion, we show for the first time that cross-linking of extracellular arabinoxylan in living maize cultures is an action of apoplastic peroxidases, some of whose unusual properties we report.
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Affiliation(s)
- Sally J Burr
- The Edinburgh Cell Wall Group, Institute of Molecular Plant Sciences, School of Biological Sciences, The University of Edinburgh, Daniel Rutherford Building, The King's Buildings, Edinburgh EH9 3JH, UK
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Boyer JS. Cell wall biosynthesis and the molecular mechanism of plant enlargement. FUNCTIONAL PLANT BIOLOGY : FPB 2009; 36:383-394. [PMID: 32688655 DOI: 10.1071/fp09048] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Accepted: 03/24/2009] [Indexed: 05/06/2023]
Abstract
Recently discovered reactions allow the green alga Chara corallina (Klien ex. Willd., em. R.D.W.) to grow well without the benefit of xyloglucan or rhamnogalactan II in its cell wall. Growth rates are controlled by polygalacturonic acid (pectate) bound with calcium in the primary wall, and the reactions remove calcium from these bonds when new pectate is supplied. The removal appears to occur preferentially in bonds distorted by wall tension produced by the turgor pressure (P). The loss of calcium accelerates irreversible wall extension if P is above a critical level. The new pectate (now calcium pectate) then binds to the wall and decelerates wall extension, depositing new wall material on and within the old wall. Together, these reactions create a non-enzymatic but stoichiometric link between wall growth and wall deposition. In green plants, pectate is one of the most conserved components of the primary wall, and it is therefore proposed that the acceleration-deceleration-wall deposition reactions are of wide occurrence likely to underlie growth in virtually all green plants. C. corallina is one of the closest relatives of the progenitors of terrestrial plants, and this review focuses on the pectate reactions and how they may fit existing theories of plant growth.
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Affiliation(s)
- John S Boyer
- College of Marine and Earth Studies and College of Agriculture and Natural Resources, University of Delaware, Lewes, DE 19958, USA. Email
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