101
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Chakrabortty B, Blilou I, Scheres B, Mulder BM. A computational framework for cortical microtubule dynamics in realistically shaped plant cells. PLoS Comput Biol 2018; 14:e1005959. [PMID: 29394250 PMCID: PMC5812663 DOI: 10.1371/journal.pcbi.1005959] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 02/14/2018] [Accepted: 01/05/2018] [Indexed: 01/07/2023] Open
Abstract
Plant morphogenesis is strongly dependent on the directional growth and the subsequent oriented division of individual cells. It has been shown that the plant cortical microtubule array plays a key role in controlling both these processes. This ordered structure emerges as the collective result of stochastic interactions between large numbers of dynamic microtubules. To elucidate this complex self-organization process a number of analytical and computational approaches to study the dynamics of cortical microtubules have been proposed. To date, however, these models have been restricted to two dimensional planes or geometrically simple surfaces in three dimensions, which strongly limits their applicability as plant cells display a wide variety of shapes. This limitation is even more acute, as both local as well as global geometrical features of cells are expected to influence the overall organization of the array. Here we describe a framework for efficiently simulating microtubule dynamics on triangulated approximations of arbitrary three dimensional surfaces. This allows the study of microtubule array organization on realistic cell surfaces obtained by segmentation of microscopic images. We validate the framework against expected or known results for the spherical and cubical geometry. We then use it to systematically study the individual contributions of global geometry, cell-edge induced catastrophes and cell-face induced stability to array organization in a cuboidal geometry. Finally, we apply our framework to analyze the highly non-trivial geometry of leaf pavement cells of Arabidopsis thaliana, Nicotiana benthamiana and Hedera helix. We show that our simulations can predict multiple features of the microtubule array structure in these cells, revealing, among others, strong constraints on the orientation of division planes.
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Affiliation(s)
- Bandan Chakrabortty
- Plant Developmental Biology, Wageningen University, Wageningen, The Netherlands
- Department of Living Matter, Institute AMOLF, Amsterdam, The Netherlands
| | - Ikram Blilou
- Laboratory of plant cell and developmental biology, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia
| | - Ben Scheres
- Plant Developmental Biology, Wageningen University, Wageningen, The Netherlands
| | - Bela M. Mulder
- Department of Living Matter, Institute AMOLF, Amsterdam, The Netherlands
- Cell Biology, Wageningen University, Wageningen, The Netherlands
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102
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Truskina J, Vernoux T. The growth of a stable stationary structure: coordinating cell behavior and patterning at the shoot apical meristem. CURRENT OPINION IN PLANT BIOLOGY 2018; 41:83-88. [PMID: 29073502 DOI: 10.1016/j.pbi.2017.09.011] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Revised: 09/27/2017] [Accepted: 09/27/2017] [Indexed: 05/23/2023]
Abstract
Plants are characterized by their ability to produce new organs post-embryonically throughout their entire life cycle. In particular development of all above-ground organs relies almost entirely on the function of the shoot apical meristem (SAM). The SAM performs a dual role by maintaining a pool of undifferentiated cells and simultaneously driving cell differentiation to initiate organogenesis. Both processes require strict coordination between individual cells which leads to formation of reproducible morphological and molecular patterns within SAM. The patterns are formed and maintained in large part due to spatio-temporal variation in signaling of plant hormones auxin and cytokinin resulting in tissue-specific transcriptional regulation. Integration of these mechanisms into computational models further identifies the key regulatory interactions involved in SAM function.
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Affiliation(s)
- Jekaterina Truskina
- Laboratoire Reproduction et Développement des Plantes, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, F-69342 Lyon, France; Centre for Plant Integrative Biology, School of Biosciences, University of Nottingham, Loughborough LE12 5RD, UK
| | - Teva Vernoux
- Laboratoire Reproduction et Développement des Plantes, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, F-69342 Lyon, France.
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103
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Roeder AH. Use it or average it: stochasticity in plant development. CURRENT OPINION IN PLANT BIOLOGY 2018; 41:8-15. [PMID: 28837855 DOI: 10.1016/j.pbi.2017.07.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2017] [Revised: 07/27/2017] [Accepted: 07/27/2017] [Indexed: 05/21/2023]
Abstract
A process that is stochastic has a probabilistic or randomly determined outcome. At the molecular level, all processes are stochastic; but development is highly reproducible, suggesting that plants and other multicellular organisms have evolved mechanisms to ensure robustness (achieving correct development despite stochastic and environmental perturbations). Mechanisms of robustness can be discovered through isolating mutants with increased variability in phenotype; such mutations do not necessarily change the average phenotype. Surprisingly, some developmental robustness mechanisms actually exploit stochasticity as a useful source of variation. For example, gene expression is stochastic and can be utilized to create subtle differences between identical cells that can initiate the patterning of specialized cell types. Stochasticity can also be used to promote robustness through spatiotemporal averaging-stochasticity can be averaged out across space and over time. Thus, organisms often harness stochasticity to ensure robust development.
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Affiliation(s)
- Adrienne Hk Roeder
- Weill Institute for Cell and Molecular Biology and School of Integrative Plant Science, Section of Plant Biology, Cornell University, 239 Weill Hall, 526 Campus Road, Ithaca, NY 14853, USA.
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104
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Liu J, Moore S, Chen C, Lindsey K. Crosstalk Complexities between Auxin, Cytokinin, and Ethylene in Arabidopsis Root Development: From Experiments to Systems Modeling, and Back Again. MOLECULAR PLANT 2017; 10:1480-1496. [PMID: 29162416 DOI: 10.1016/j.molp.2017.11.002] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2017] [Revised: 11/06/2017] [Accepted: 11/07/2017] [Indexed: 05/23/2023]
Abstract
Understanding how hormones and genes interact to coordinate plant growth in a changing environment is a major challenge in plant developmental biology. Auxin, cytokinin, and ethylene are three important hormones that regulate many aspects of plant development. This review critically evaluates the crosstalk between the three hormones in Arabidopsis root development. We integrate a variety of experimental data into a crosstalk network, which reveals multiple layers of complexity in auxin, cytokinin, and ethylene crosstalk. In particular, data integration reveals an additional, largely overlooked link between the ethylene and cytokinin pathways, which acts through a phosphorelay mechanism. This proposed link addresses outstanding questions on whether ethylene application promotes or inhibits receptor kinase activity of the ethylene receptors. Elucidating the complexity in auxin, cytokinin, and ethylene crosstalk requires a combined experimental and systems modeling approach. We evaluate important modeling efforts for establishing how crosstalk between auxin, cytokinin, and ethylene regulates patterning in root development. We discuss how a novel methodology that iteratively combines experiments with systems modeling analysis is essential for elucidating the complexity in crosstalk of auxin, cytokinin, and ethylene in root development. Finally, we discuss the future challenges from a combined experimental and modeling perspective.
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Affiliation(s)
- Junli Liu
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
| | - Simon Moore
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
| | - Chunli Chen
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, China.
| | - Keith Lindsey
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK.
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105
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Carter R, Sánchez-Corrales YE, Hartley M, Grieneisen VA, Marée AFM. Pavement cells and the topology puzzle. Development 2017; 144:4386-4397. [PMID: 29084800 PMCID: PMC5769637 DOI: 10.1242/dev.157073] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 10/24/2017] [Indexed: 01/14/2023]
Abstract
D'Arcy Thompson emphasised the importance of surface tension as a potential driving force in establishing cell shape and topology within tissues. Leaf epidermal pavement cells grow into jigsaw-piece shapes, highly deviating from such classical forms. We investigate the topology of developing Arabidopsis leaves composed solely of pavement cells. Image analysis of around 50,000 cells reveals a clear and unique topological signature, deviating from previously studied epidermal tissues. This topological distribution is established early during leaf development, already before the typical pavement cell shapes emerge, with topological homeostasis maintained throughout growth and unaltered between division and maturation zones. Simulating graph models, we identify a heuristic cellular division rule that reproduces the observed topology. Our parsimonious model predicts how and when cells effectively place their division plane with respect to their neighbours. We verify the predicted dynamics through in vivo tracking of 800 mitotic events, and conclude that the distinct topology is not a direct consequence of the jigsaw piece-like shape of the cells, but rather owes itself to a strongly life history-driven process, with limited impact from cell-surface mechanics.
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Affiliation(s)
- Ross Carter
- Computational and Systems Biology, John Innes Centre, Norwich NR4 7UH, UK
| | | | - Matthew Hartley
- Computational and Systems Biology, John Innes Centre, Norwich NR4 7UH, UK
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106
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Gaillochet C, Stiehl T, Wenzl C, Ripoll JJ, Bailey-Steinitz LJ, Li L, Pfeiffer A, Miotk A, Hakenjos JP, Forner J, Yanofsky MF, Marciniak-Czochra A, Lohmann JU. Control of plant cell fate transitions by transcriptional and hormonal signals. eLife 2017; 6:30135. [PMID: 29058667 PMCID: PMC5693117 DOI: 10.7554/elife.30135] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2017] [Accepted: 10/22/2017] [Indexed: 11/24/2022] Open
Abstract
Plant meristems carry pools of continuously active stem cells, whose activity is controlled by developmental and environmental signals. After stem cell division, daughter cells that exit the stem cell domain acquire transit amplifying cell identity before they are incorporated into organs and differentiate. In this study, we used an integrated approach to elucidate the role of HECATE (HEC) genes in regulating developmental trajectories of shoot stem cells in Arabidopsis thaliana. Our work reveals that HEC function stabilizes cell fate in distinct zones of the shoot meristem thereby controlling the spatio-temporal dynamics of stem cell differentiation. Importantly, this activity is concomitant with the local modulation of cellular responses to cytokinin and auxin, two key phytohormones regulating cell behaviour. Mechanistically, we show that HEC factors transcriptionally control and physically interact with MONOPTEROS (MP), a key regulator of auxin signalling, and modulate the autocatalytic stabilization of auxin signalling output. Unlike animals, plants continuously generate new organs that make up their body. At the core of this amazing capacity lie tissues called meristems, which are found at the growing tips of all plants. Meristems contain dividing stem cells. The daughters of these stem cells pass through nearby regions called transition domains. Over time, they change – or differentiate – to go on to become part of tissues like leaves, roots, stems, shoots, flowers or fruits. Stem cell differentiation has a direct impact on a plant’s architecture and eventually its reproductive success. For crops, these factors determine yield. This means that understanding this aspect of plant development is central to basic and applied plant biology. Many factors required for shoot meristem activity have been identified, with a focus so far on the processes that control the identity of the cells produced. Now, Gaillochet et al. have asked which genes are responsible for controlling when stem cells in meristems differentiate. The analysis focused on the meristem that makes all the above ground parts of model plant Arabidopsis thaliana – the shoot apical meristem. Gaillochet et al. found that HECATE genes (or HEC for short) control the timing of stem cell differentiation by regulating the balance between the activities of two plant hormones: cytokinin and auxin. These genes promote cytokinin signals at the centre of the meristem, and dampen auxin response at the edges. This acts to slow down cell differentiation in two key transition domains of the shoot meristem. These new findings provide a molecular framework that now can be further investigated in crop plants to try to improve their yield. The findings also lay the foundation for studies of animals that may define common principles shared among stem cell systems in organisms that diverged over a billion years ago.
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Affiliation(s)
- Christophe Gaillochet
- Department of Stem Cell Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Thomas Stiehl
- Institute of Applied Mathematics, Heidelberg University, Heidelberg, Germany.,Interdisciplinary Center for Scientific Computing, Heidelberg University, Heidelberg, Germany
| | - Christian Wenzl
- Department of Stem Cell Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Juan-José Ripoll
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, San Diego, United States
| | - Lindsay J Bailey-Steinitz
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, San Diego, United States
| | - Lanxin Li
- Department of Stem Cell Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Anne Pfeiffer
- Department of Stem Cell Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Andrej Miotk
- Department of Stem Cell Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Jana P Hakenjos
- Department of Stem Cell Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Joachim Forner
- Department of Stem Cell Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
| | - Martin F Yanofsky
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California, San Diego, San Diego, United States
| | - Anna Marciniak-Czochra
- Institute of Applied Mathematics, Heidelberg University, Heidelberg, Germany.,Interdisciplinary Center for Scientific Computing, Heidelberg University, Heidelberg, Germany.,Bioquant Center, Heidelberg University, Heidelberg, Germany
| | - Jan U Lohmann
- Department of Stem Cell Biology, Centre for Organismal Studies, University of Heidelberg, Heidelberg, Germany
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107
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Qi J, Wu B, Feng S, Lü S, Guan C, Zhang X, Qiu D, Hu Y, Zhou Y, Li C, Long M, Jiao Y. Mechanical regulation of organ asymmetry in leaves. NATURE PLANTS 2017; 3:724-733. [PMID: 29150691 DOI: 10.1038/s41477-017-0008-6] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 07/28/2017] [Indexed: 05/08/2023]
Abstract
How appendages, such as plant leaves or animal limbs, develop asymmetric shapes remains a fundamental question in biology. Although ongoing research has revealed the genetic regulation of organ pattern formation, how gene activity ultimately directs organ shape remains unclear. Here, we show that leaf dorsoventral (adaxial-abaxial) polarity signals lead to mechanical heterogeneity of the cell wall, related to the methyl-esterification of cell-wall pectins in tomato and Arabidopsis. Numerical simulations predicate that mechanical heterogeneity is sufficient to produce the asymmetry seen in planar leaves. Experimental tests that alter pectin methyl-esterification, and therefore cell wall mechanical properties, support this model and lead to polar changes in gene expression, suggesting the existence of a feedback mechanism for mechanical signals in morphogenesis. Thus, mechanical heterogeneity within tissue may underlie organ shape asymmetry.
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Affiliation(s)
- Jiyan Qi
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and National Center for Plant Gene Research, 100101, Beijing, China
| | - Binbin Wu
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and National Center for Plant Gene Research, 100101, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Shiliang Feng
- Key Laboratory of Microgravity (National Microgravity Laboratory), Center of Biomechanics and Bioengineering, and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Shouqin Lü
- University of Chinese Academy of Sciences, 100049, Beijing, China
- Key Laboratory of Microgravity (National Microgravity Laboratory), Center of Biomechanics and Bioengineering, and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Chunmei Guan
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and National Center for Plant Gene Research, 100101, Beijing, China
| | - Xiao Zhang
- University of Chinese Academy of Sciences, 100049, Beijing, China
- Key Laboratory of Microgravity (National Microgravity Laboratory), Center of Biomechanics and Bioengineering, and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, 100190, Beijing, China
| | - Dengli Qiu
- Bruker Nano Surfaces Business, 100081, Beijing, China
| | - Yingchun Hu
- College of Life Sciences, Peking University, 100871, Beijing, China
| | - Yihua Zhou
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and National Center for Plant Gene Research, 100101, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Chuanyou Li
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and National Center for Plant Gene Research, 100101, Beijing, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Mian Long
- University of Chinese Academy of Sciences, 100049, Beijing, China.
- Key Laboratory of Microgravity (National Microgravity Laboratory), Center of Biomechanics and Bioengineering, and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, 100190, Beijing, China.
| | - Yuling Jiao
- State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and National Center for Plant Gene Research, 100101, Beijing, China.
- University of Chinese Academy of Sciences, 100049, Beijing, China.
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108
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Abstract
There is increasing evidence that all cells sense mechanical forces in order to perform their functions. In animals, mechanotransduction has been studied during the establishment of cell polarity, fate, and division in single cells, and increasingly is studied in the context of a multicellular tissue. What about plant systems? Our goal in this review is to summarize what is known about the perception of mechanical cues in plants, and to provide a brief comparison with animals.
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Affiliation(s)
- Olivier Hamant
- Laboratoire Reproduction et Développement des Plantes, University Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, F-69342, Lyon, France.
| | - Elizabeth S Haswell
- Department of Biology, Washington University in Saint Louis, Mailbox 1137, Saint Louis, MO, 63130, USA.
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109
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Hamant O, Haswell ES. Life behind the wall: sensing mechanical cues in plants. BMC Biol 2017. [PMID: 28697754 DOI: 10.1186/s12915-017-0403-405] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
There is increasing evidence that all cells sense mechanical forces in order to perform their functions. In animals, mechanotransduction has been studied during the establishment of cell polarity, fate, and division in single cells, and increasingly is studied in the context of a multicellular tissue. What about plant systems? Our goal in this review is to summarize what is known about the perception of mechanical cues in plants, and to provide a brief comparison with animals.
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Affiliation(s)
- Olivier Hamant
- Laboratoire Reproduction et Développement des Plantes, University Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, F-69342, Lyon, France.
| | - Elizabeth S Haswell
- Department of Biology, Washington University in Saint Louis, Mailbox 1137, Saint Louis, MO, 63130, USA.
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110
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Jackson MD, Xu H, Duran-Nebreda S, Stamm P, Bassel GW. Topological analysis of multicellular complexity in the plant hypocotyl. eLife 2017; 6. [PMID: 28682235 PMCID: PMC5499946 DOI: 10.7554/elife.26023] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 06/13/2017] [Indexed: 12/12/2022] Open
Abstract
Multicellularity arose as a result of adaptive advantages conferred to complex cellular assemblies. The arrangement of cells within organs endows higher-order functionality through a structure-function relationship, though the organizational properties of these multicellular configurations remain poorly understood. We investigated the topological properties of complex organ architecture by digitally capturing global cellular interactions in the plant embryonic stem (hypocotyl), and analyzing these using quantitative network analysis. This revealed the presence of coherent conduits of reduced path length across epidermal atrichoblast cell files. The preferential movement of small molecules along this cell type was demonstrated using fluorescence transport assays. Both robustness and plasticity in this higher order property of atrichoblast patterning was observed across diverse genetic backgrounds, and the analysis of genetic patterning mutants identified the contribution of gene activity towards their construction. This topological analysis of multicellular structural organization reveals higher order functions for patterning and principles of complex organ construction.
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Affiliation(s)
- Matthew Db Jackson
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Hao Xu
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | | | - Petra Stamm
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - George W Bassel
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
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111
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112
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Peyraud R, Dubiella U, Barbacci A, Genin S, Raffaele S, Roby D. Advances on plant-pathogen interactions from molecular toward systems biology perspectives. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 90:720-737. [PMID: 27870294 PMCID: PMC5516170 DOI: 10.1111/tpj.13429] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 11/14/2016] [Accepted: 11/14/2016] [Indexed: 05/21/2023]
Abstract
In the past 2 decades, progress in molecular analyses of the plant immune system has revealed key elements of a complex response network. Current paradigms depict the interaction of pathogen-secreted molecules with host target molecules leading to the activation of multiple plant response pathways. Further research will be required to fully understand how these responses are integrated in space and time, and exploit this knowledge in agriculture. In this review, we highlight systems biology as a promising approach to reveal properties of molecular plant-pathogen interactions and predict the outcome of such interactions. We first illustrate a few key concepts in plant immunity with a network and systems biology perspective. Next, we present some basic principles of systems biology and show how they allow integrating multiomics data and predict cell phenotypes. We identify challenges for systems biology of plant-pathogen interactions, including the reconstruction of multiscale mechanistic models and the connection of host and pathogen models. Finally, we outline studies on resistance durability through the robustness of immune system networks, the identification of trade-offs between immunity and growth and in silico plant-pathogen co-evolution as exciting perspectives in the field. We conclude that the development of sophisticated models of plant diseases incorporating plant, pathogen and climate properties represent a major challenge for agriculture in the future.
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Affiliation(s)
- Rémi Peyraud
- LIPMUniversité de ToulouseINRACNRSCastanet‐TolosanFrance
| | | | | | - Stéphane Genin
- LIPMUniversité de ToulouseINRACNRSCastanet‐TolosanFrance
| | | | - Dominique Roby
- LIPMUniversité de ToulouseINRACNRSCastanet‐TolosanFrance
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113
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Zhang T, Vavylonis D, Durachko DM, Cosgrove DJ. Nanoscale movements of cellulose microfibrils in primary cell walls. NATURE PLANTS 2017; 3:17056. [PMID: 28452988 PMCID: PMC5478883 DOI: 10.1038/nplants.2017.56] [Citation(s) in RCA: 79] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 03/22/2017] [Indexed: 05/18/2023]
Abstract
The growing plant cell wall is commonly considered to be a fibre-reinforced structure whose strength, extensibility and anisotropy depend on the orientation of crystalline cellulose microfibrils, their bonding to the polysaccharide matrix and matrix viscoelasticity1-4. Structural reinforcement of the wall by stiff cellulose microfibrils is central to contemporary models of plant growth, mechanics and meristem dynamics4-12. Although passive microfibril reorientation during wall extension has been inferred from theory and from bulk measurements13-15, nanometre-scale movements of individual microfibrils have not been directly observed. Here we combined nanometre-scale imaging of wet cell walls by atomic force microscopy (AFM) with a stretching device and endoglucanase treatment that induces wall stress relaxation and creep, mimicking wall behaviours during cell growth. Microfibril movements during forced mechanical extensions differ from those during creep of the enzymatically loosened wall. In addition to passive angular reorientation, we observed a diverse repertoire of microfibril movements that reveal the spatial scale of molecular connections between microfibrils. Our results show that wall loosening alters microfibril connectivity, enabling microfibril dynamics not seen during mechanical stretch. These insights into microfibril movements and connectivities need to be incorporated into refined models of plant cell wall structure, growth and morphogenesis.
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Affiliation(s)
- Tian Zhang
- Department of Biology and Center for Lignocellulose Structure and Formation, 208 Mueller Laboratory, Penn State University, University Park, PA 16802 USA
| | | | - Daniel M. Durachko
- Department of Biology and Center for Lignocellulose Structure and Formation, 208 Mueller Laboratory, Penn State University, University Park, PA 16802 USA
| | - Daniel J. Cosgrove
- Department of Biology and Center for Lignocellulose Structure and Formation, 208 Mueller Laboratory, Penn State University, University Park, PA 16802 USA
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114
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Cell-size dependent progression of the cell cycle creates homeostasis and flexibility of plant cell size. Nat Commun 2017; 8:15060. [PMID: 28447614 PMCID: PMC5414177 DOI: 10.1038/ncomms15060] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 02/23/2017] [Indexed: 11/09/2022] Open
Abstract
Mean cell size at division is generally constant for specific conditions and cell types, but the mechanisms coupling cell growth and cell cycle control with cell size regulation are poorly understood in intact tissues. Here we show that the continuously dividing fields of cells within the shoot apical meristem of Arabidopsis show dynamic regulation of mean cell size dependent on developmental stage, genotype and environmental signals. We show cell size at division and cell cycle length is effectively predicted using a two-stage cell cycle model linking cell growth and two sequential cyclin dependent kinase (CDK) activities, and experimental results concur in showing that progression through both G1/S and G2/M is size dependent. This work shows that cell-autonomous co-ordination of cell growth and cell division previously observed in unicellular organisms also exists in intact plant tissues, and that cell size may be an emergent rather than directly determined property of cells.
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115
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Boyd ARB, Moore S, Sader JE, Lee PVS. Modelling apical columnar epithelium mechanics from circumferential contractile fibres. Biomech Model Mechanobiol 2017; 16:1555-1568. [PMID: 28389829 DOI: 10.1007/s10237-017-0905-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2016] [Accepted: 03/27/2017] [Indexed: 11/26/2022]
Abstract
Simple columnar epithelia are formed by individual epithelial cells connecting together to form single cell high sheets. They are a main component of many important body tissues and are heavily involved in both normal and cancerous cell activities. Prior experimental observations have identified a series of contractile fibres around the circumference of a cross section located in the upper (apical) region of each cell. While other potential mechanisms have been identified in both the experimental and theoretical literature, these circumferential fibres are considered to be the most likely mechanism controlling movement of this cross section. Here, we investigated the impact of circumferential contractile fibres on movement of the cross section by creating an alternate model where movement is driven from circumferential contractile fibres, without any other potential mechanisms. In this model, we utilised a circumferential contractile fibre representation based on investigations into the movement of contractile fibres as an individual system, treated circumferential fibres as a series of units, and matched our model simulation to experimental geometries. By testing against laser ablation datasets sourced from existing literature, we found that circumferential fibres can reproduce the majority of cross-sectional movements. We also investigated model predictions related to various aspects of cross-sectional movement, providing insights into epithelium mechanics and demonstrating the usefulness of our modelling approach.
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Affiliation(s)
- A R B Boyd
- Department of Mechanical Engineering, University of Melbourne, Melbourne, VIC, 3010, Australia
| | - S Moore
- IBM Research Australia, Level 5, 204 Lygon Street, Carlton, VIC, 3010, Australia
| | - J E Sader
- School of Mathematics and Statistics, University of Melbourne, Melbourne, VIC, 3010, Australia
| | - P V S Lee
- Department of Mechanical Engineering, University of Melbourne, Melbourne, VIC, 3010, Australia.
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Bringmann M, Bergmann DC. Tissue-wide Mechanical Forces Influence the Polarity of Stomatal Stem Cells in Arabidopsis. Curr Biol 2017; 27:877-883. [DOI: 10.1016/j.cub.2017.01.059] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 01/05/2017] [Accepted: 01/27/2017] [Indexed: 10/20/2022]
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Pfeiffer A, Wenzl C, Lohmann JU. Beyond flexibility: controlling stem cells in an ever changing environment. CURRENT OPINION IN PLANT BIOLOGY 2017; 35:117-123. [PMID: 27918940 DOI: 10.1016/j.pbi.2016.11.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 11/14/2016] [Accepted: 11/21/2016] [Indexed: 06/06/2023]
Abstract
Developmental plasticity is a defining feature of plants allowing them to colonize a wide range of different ecosystems by promoting environmental adaptation. Their postembryonic development requires life-long maintenance of stem cells, which are embedded into specialized tissues, called meristems. The shoot apical meristem gives rise to all above ground tissues and is a complex and dynamic three-dimensional structure harboring cells of different clonal origins and fates. Functionally divergent subdomains are stably maintained despite permanent cell division, however their relative sizes are modified in response to developmental and environmental signals. In this review, we briefly describe the core regulatory program of the shoot apical meristem and discuss progress in the fields of mechanical and environmental control of its activity.
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Affiliation(s)
- Anne Pfeiffer
- Department of Stem Cell Biology, Centre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany
| | - Christian Wenzl
- Department of Stem Cell Biology, Centre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany
| | - Jan U Lohmann
- Department of Stem Cell Biology, Centre for Organismal Studies, University of Heidelberg, D-69120 Heidelberg, Germany.
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Bayer M, Slane D, Jürgens G. Early plant embryogenesis-dark ages or dark matter? CURRENT OPINION IN PLANT BIOLOGY 2017; 35:30-36. [PMID: 27810634 DOI: 10.1016/j.pbi.2016.10.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 10/11/2016] [Accepted: 10/13/2016] [Indexed: 05/11/2023]
Abstract
In nearly all flowering plants, the basic body plan is laid down during embryogenesis. In Arabidopsis, the crucial cell types are established extremely early as reflected in the stereotypic sequence of oriented cell divisions in the developing young embryo. Research into early embryogenesis was especially focused on the role of the infamous tryptophan derivative auxin in establishing embryo polarity and generating the main body axis. However, it is becoming obvious that the mere link to auxin does not provide any mechanistic understanding of early embryo patterning. Taking recent research into account, we discuss mechanisms underlying early embryonic patterning from an evolutionary perspective.
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Affiliation(s)
- Martin Bayer
- Department of Cell Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Daniel Slane
- Department of Cell Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany
| | - Gerd Jürgens
- Department of Cell Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany; Department of Developmental Genetics, Center for Plant Molecular Biology, University of Tübingen, 72076 Tübingen, Germany.
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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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Hamant O, Moulia B. How do plants read their own shapes? THE NEW PHYTOLOGIST 2016; 212:333-7. [PMID: 27532273 DOI: 10.1111/nph.14143] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 06/27/2016] [Indexed: 05/26/2023]
Abstract
Contents 333 I. 333 II. 334 III. 334 IV. 336 336 References 337 SUMMARY: Although the sensing of shape and deformation was historically involved in the control of animal locomotion, it is now increasingly being incorporated in developmental biology. Proprioception, the perception of the self, is particularly key to the question of the reproducibility of shapes: the many regulators of growth may lead to a large array of geometries, but shape sensing restricts these diverse outputs to a limited number of forms. Mechanistically, and in addition to geometrical feedback onto the diffusion and transport of molecular factors, we highlight the role of shape-derived mechanical stress and strain in this process. Through examples at the cell, tissue and organism scales, it appears that such mechanical feedback adds robustness to morphogenesis. Interestingly, synergies exist between shape sensing and response to external cues, such as wind and gravity. Understanding the molecular basis of proprioception is now within reach and opens up many avenues for an integrative view of development.
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Affiliation(s)
- Olivier Hamant
- Laboratoire Reproduction et Développement des Plantes, Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRA, F-69342, Lyon, France.
| | - Bruno Moulia
- UCA, INRA, UMR PIAF, 63000, Clermont-Ferrand, France
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