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Ohmura T, Skinner DJ, Neuhaus K, Choi GPT, Dunkel J, Drescher K. In vivo Microrheology Reveals Local Elastic and Plastic Responses Inside Three-dimensional Bacterial Biofilms. Adv Mater 2024:e2314059. [PMID: 38511867 DOI: 10.1002/adma.202314059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 03/08/2024] [Indexed: 03/22/2024]
Abstract
Bacterial biofilms are highly abundant three-dimensional (3D) living materials capable of performing complex biomechanical and biochemical functions, including programmable growth, self-repair, filtration, and bioproduction. Methods to measure internal mechanical properties of biofilms in vivo with spatial resolution on the cellular scale have been lacking. Here, we tracked thousands of cells inside living 3D biofilms of the bacterium Vibrio cholerae during and after the application of shear stress, for a wide range of stress amplitudes, periods, and biofilm sizes, which revealed anisotropic elastic and plastic responses of both cell displacements and cell reorientations. Using cellular tracking to infer parameters of a general mechanical model, we obtained spatially-resolved measurements of the elastic modulus inside the biofilm, which correlate with the spatial distribution of the polysaccharides within the biofilm matrix. The non-invasive microrheology and force-inference approach introduced here provides a general framework for studying mechanical properties with high spatial resolution in living materials. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Takuya Ohmura
- Biozentrum, University of Basel, Spitalstrasse 41, Basel, Switzerland
| | - Dominic J Skinner
- Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, USA
- NSF-Simons Center for Quantitative Biology, Northwestern University, Evanston, USA
| | - Konstantin Neuhaus
- Biozentrum, University of Basel, Spitalstrasse 41, Basel, Switzerland
- Department of Physics, Philipps-Universität Marburg, Renthof 5, Marburg, Germany
| | - Gary P T Choi
- Department of Mathematics, The Chinese University of Hong Kong, Hong Kong
| | - Jörn Dunkel
- Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, USA
| | - Knut Drescher
- Biozentrum, University of Basel, Spitalstrasse 41, Basel, Switzerland
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2
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Jeckel H, Nosho K, Neuhaus K, Hastewell AD, Skinner DJ, Saha D, Netter N, Paczia N, Dunkel J, Drescher K. Simultaneous spatiotemporal transcriptomics and microscopy of Bacillus subtilis swarm development reveal cooperation across generations. Nat Microbiol 2023; 8:2378-2391. [PMID: 37973866 PMCID: PMC10686836 DOI: 10.1038/s41564-023-01518-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 10/09/2023] [Indexed: 11/19/2023]
Abstract
Development of microbial communities is a complex multiscale phenomenon with wide-ranging biomedical and ecological implications. How biological and physical processes determine emergent spatial structures in microbial communities remains poorly understood due to a lack of simultaneous measurements of gene expression and cellular behaviour in space and time. Here we combined live-cell microscopy with a robotic arm for spatiotemporal sampling, which enabled us to simultaneously acquire phenotypic imaging data and spatiotemporal transcriptomes during Bacillus subtilis swarm development. Quantitative characterization of the spatiotemporal gene expression patterns revealed correlations with cellular and collective properties, and phenotypic subpopulations. By integrating these data with spatiotemporal metabolome measurements, we discovered a spatiotemporal cross-feeding mechanism fuelling swarm development: during their migration, earlier generations deposit metabolites which are consumed by later generations that swarm across the same location. These results highlight the importance of spatiotemporal effects during the emergence of phenotypic subpopulations and their interactions in bacterial communities.
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Affiliation(s)
- Hannah Jeckel
- Biozentrum, University of Basel, Basel, Switzerland
- Department of Physics, Philipps-Universität Marburg, Marburg, Germany
| | - Kazuki Nosho
- Biozentrum, University of Basel, Basel, Switzerland
| | - Konstantin Neuhaus
- Biozentrum, University of Basel, Basel, Switzerland
- Department of Physics, Philipps-Universität Marburg, Marburg, Germany
| | - Alasdair D Hastewell
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Dominic J Skinner
- NSF-Simons Center for Quantitative Biology, Northwestern University, Evanston, IL, USA
| | - Dibya Saha
- Biozentrum, University of Basel, Basel, Switzerland
| | | | - Nicole Paczia
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Jörn Dunkel
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA, USA.
| | - Knut Drescher
- Biozentrum, University of Basel, Basel, Switzerland.
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3
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Skinner DJ, Jeckel H, Martin AC, Drescher K, Dunkel J. Topological packing statistics of living and nonliving matter. Sci Adv 2023; 9:eadg1261. [PMID: 37672580 PMCID: PMC10482333 DOI: 10.1126/sciadv.adg1261] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Accepted: 07/27/2023] [Indexed: 09/08/2023]
Abstract
Complex disordered matter is of central importance to a wide range of disciplines, from bacterial colonies and embryonic tissues in biology to foams and granular media in materials science to stellar configurations in astrophysics. Because of the vast differences in composition and scale, comparing structural features across such disparate systems remains challenging. Here, by using the statistical properties of Delaunay tessellations, we introduce a mathematical framework for measuring topological distances between general three-dimensional point clouds. The resulting system-agnostic metric reveals subtle structural differences between bacterial biofilms as well as between zebrafish brain regions, and it recovers temporal ordering of embryonic development. We apply the metric to construct a universal topological atlas encompassing bacterial biofilms, snowflake yeast, plant shoots, zebrafish brain matter, organoids, and embryonic tissues as well as foams, colloidal packings, glassy materials, and stellar configurations. Living systems localize within a bounded island-like region of the atlas, reflecting that biological growth mechanisms result in characteristic topological properties.
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Affiliation(s)
- Dominic J Skinner
- Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
- NSF-Simons Center for Quantitative Biology, Northwestern University, 2205 Tech Drive, Evanston, IL 60208, USA
| | - Hannah Jeckel
- Department of Physics, Philipps-Universität Marburg, Renthof 6, 35032 Marburg, Germany
- Biozentrum, University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
| | - Adam C Martin
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA
| | - Knut Drescher
- Biozentrum, University of Basel, Spitalstrasse 41, 4056 Basel, Switzerland
| | - Jörn Dunkel
- Department of Mathematics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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Kim H, Skinner DJ, Glass DS, Hamby AE, Stuart BAR, Dunkel J, Riedel-Kruse IH. 4-bit adhesion logic enables universal multicellular interface patterning. Nature 2022; 608:324-329. [PMID: 35948712 PMCID: PMC9365691 DOI: 10.1038/s41586-022-04944-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 06/07/2022] [Indexed: 01/01/2023]
Abstract
Multicellular systems, from bacterial biofilms to human organs, form interfaces (or boundaries) between different cell collectives to spatially organize versatile functions1,2. The evolution of sufficiently descriptive genetic toolkits probably triggered the explosion of complex multicellular life and patterning3,4. Synthetic biology aims to engineer multicellular systems for practical applications and to serve as a build-to-understand methodology for natural systems5–8. However, our ability to engineer multicellular interface patterns2,9 is still very limited, as synthetic cell–cell adhesion toolkits and suitable patterning algorithms are underdeveloped5,7,10–13. Here we introduce a synthetic cell–cell adhesin logic with swarming bacteria and establish the precise engineering, predictive modelling and algorithmic programming of multicellular interface patterns. We demonstrate interface generation through a swarming adhesion mechanism, quantitative control over interface geometry and adhesion-mediated analogues of developmental organizers and morphogen fields. Using tiling and four-colour-mapping concepts, we identify algorithms for creating universal target patterns. This synthetic 4-bit adhesion logic advances practical applications such as human-readable molecular diagnostics, spatial fluid control on biological surfaces and programmable self-growing materials5–8,14. Notably, a minimal set of just four adhesins represents 4 bits of information that suffice to program universal tessellation patterns, implying a low critical threshold for the evolution and engineering of complex multicellular systems3,5. A synthetic cell-cell adhesion logic using swarming E. coli with 4 bits of information is introduced, enabling the programming of interfaces that combine to form universal tessellation patterns over a large scale.
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Affiliation(s)
- Honesty Kim
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Dominic J Skinner
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - David S Glass
- Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Alexander E Hamby
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Bradey A R Stuart
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA
| | - Jörn Dunkel
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Ingmar H Riedel-Kruse
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA. .,Department of Applied Mathematics, University of Arizona, Tucson, AZ, USA. .,Department of Biomedical Engineering, University of Arizona, Tucson, AZ, USA.
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5
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Skinner DJ, Dunkel J. Estimating Entropy Production from Waiting Time Distributions. Phys Rev Lett 2021; 127:198101. [PMID: 34797138 DOI: 10.1103/physrevlett.127.198101] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2021] [Accepted: 08/17/2021] [Indexed: 06/13/2023]
Abstract
Living systems operate far from thermal equilibrium by converting the chemical potential of ATP into mechanical work to achieve growth, replication, or locomotion. Given time series observations of intra-, inter-, or multicellular processes, a key challenge is to detect nonequilibrium behavior and quantify the rate of free energy consumption. Obtaining reliable bounds on energy consumption and entropy production directly from experimental data remains difficult in practice, as many degrees of freedom typically are hidden to the observer, so that the accessible coarse-grained dynamics may not obviously violate detailed balance. Here, we introduce a novel method for bounding the entropy production of physical and living systems which uses only the waiting time statistics of hidden Markov processes and, hence, can be directly applied to experimental data. By determining a universal limiting curve, we infer entropy production bounds from experimental data for gene regulatory networks, mammalian behavioral dynamics, and numerous other biological processes. Further considering the asymptotic limit of increasingly precise biological timers, we estimate the necessary entropic cost of heartbeat regulation in humans, dogs, and mice.
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Affiliation(s)
- Dominic J Skinner
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA
| | - Jörn Dunkel
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA
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6
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Abstract
Living systems maintain or increase local order by working against the second law of thermodynamics. Thermodynamic consistency is restored as they consume free energy, thereby increasing the net entropy of their environment. Recently introduced estimators for the entropy production rate have provided major insights into the efficiency of important cellular processes. In experiments, however, many degrees of freedom typically remain hidden to the observer, and, in these cases, existing methods are not optimal. Here, by reformulating the problem within an optimization framework, we are able to infer improved bounds on the rate of entropy production from partial measurements of biological systems. Our approach yields provably optimal estimates given certain measurable transition statistics. In contrast to prevailing methods, the improved estimator reveals nonzero entropy production rates even when nonequilibrium processes appear time symmetric and therefore may pretend to obey detailed balance. We demonstrate the broad applicability of this framework by providing improved bounds on the energy consumption rates in a diverse range of biological systems including bacterial flagella motors, growing microtubules, and calcium oscillations within human embryonic kidney cells.
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Affiliation(s)
- Dominic J Skinner
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - Jörn Dunkel
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139
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7
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Skinner DJ, Song B, Jeckel H, Jelli E, Drescher K, Dunkel J. Topological Metric Detects Hidden Order in Disordered Media. Phys Rev Lett 2021; 126:048101. [PMID: 33576647 DOI: 10.1103/physrevlett.126.048101] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 10/15/2020] [Accepted: 11/18/2020] [Indexed: 06/12/2023]
Abstract
Recent advances in microscopy techniques make it possible to study the growth, dynamics, and response of complex biophysical systems at single-cell resolution, from bacterial communities to tissues and organoids. In contrast to ordered crystals, it is less obvious how one can reliably distinguish two amorphous yet structurally different cellular materials. Here, we introduce a topological earth mover's (TEM) distance between disordered structures that compares local graph neighborhoods of the microscopic cell-centroid networks. Leveraging structural information contained in the neighborhood motif distributions, the TEM metric allows an interpretable reconstruction of equilibrium and nonequilibrium phase spaces and embedded pathways from static system snapshots alone. Applied to cell-resolution imaging data, the framework recovers time ordering without prior knowledge about the underlying dynamics, revealing that fly wing development solves a topological optimal transport problem. Extending our topological analysis to bacterial swarms, we find a universal neighborhood size distribution consistent with a Tracy-Widom law.
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Affiliation(s)
- Dominic J Skinner
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA
| | - Boya Song
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA
| | - Hannah Jeckel
- Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
- Department of Physics, Philipps-Universität Marburg, 35043 Marburg, Germany
| | - Eric Jelli
- Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
- Department of Physics, Philipps-Universität Marburg, 35043 Marburg, Germany
| | - Knut Drescher
- Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
- Department of Physics, Philipps-Universität Marburg, 35043 Marburg, Germany
| | - Jörn Dunkel
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA
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8
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Pearce P, Song B, Skinner DJ, Mok R, Hartmann R, Singh PK, Jeckel H, Oishi JS, Drescher K, Dunkel J. Flow-Induced Symmetry Breaking in Growing Bacterial Biofilms. Phys Rev Lett 2019; 123:258101. [PMID: 31922766 DOI: 10.1103/physrevlett.123.258101] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Indexed: 06/10/2023]
Abstract
Bacterial biofilms represent a major form of microbial life on Earth and serve as a model active nematic system, in which activity results from growth of the rod-shaped bacterial cells. In their natural environments, ranging from human organs to industrial pipelines, biofilms have evolved to grow robustly under significant fluid shear. Despite intense practical and theoretical interest, it is unclear how strong fluid flow alters the local and global architectures of biofilms. Here, we combine highly time-resolved single-cell live imaging with 3D multiscale modeling to investigate the mechanisms by which flow affects the dynamics of all individual cells in growing biofilms. Our experiments and cell-based simulations reveal three quantitatively different growth phases in strong external flow and the transitions between them. In the initial stages of biofilm development, flow induces a downstream gradient in cell orientation, causing asymmetrical dropletlike biofilm shapes. In the later developmental stages, when the majority of cells are sheltered from the flow by the surrounding extracellular matrix, buckling-induced cell verticalization in the biofilm core restores radially symmetric biofilm growth, in agreement with predictions of a 3D continuum model.
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Affiliation(s)
- Philip Pearce
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge Massachusetts 02139-4307, USA
| | - Boya Song
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge Massachusetts 02139-4307, USA
| | - Dominic J Skinner
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge Massachusetts 02139-4307, USA
| | - Rachel Mok
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge Massachusetts 02139-4307, USA
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA
| | - Raimo Hartmann
- Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
| | - Praveen K Singh
- Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
| | - Hannah Jeckel
- Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
- Department of Physics, Philipps-Universität Marburg, 35043 Marburg, Germany
| | - Jeffrey S Oishi
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge Massachusetts 02139-4307, USA
- Department of Physics, Bates College, Lewiston, Maine 04240, USA
| | - Knut Drescher
- Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
- Department of Physics, Philipps-Universität Marburg, 35043 Marburg, Germany
| | - Jörn Dunkel
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge Massachusetts 02139-4307, USA
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9
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Skinner DJ, Baker SC, Meister RJ, Broadhvest J, Schneitz K, Gasser CS. The Arabidopsis HUELLENLOS gene, which is essential for normal ovule development, encodes a mitochondrial ribosomal protein. Plant Cell 2001. [PMID: 11752383 DOI: 10.1105/tpc.13.12.2719] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The HUELLENLOS (HLL) gene participates in patterning and growth of the Arabidopsis ovule. We have isolated the HLL gene and shown that it encodes a protein homologous to the L14 proteins of eubacterial ribosomes. The Arabidopsis genome also includes a highly similar gene, HUELLENLOS PARALOG (HLP), and genes for both cytosolic (L23) and chloroplast ribosome L14 proteins. Phylogenetic analysis shows that HLL and HLP differ significantly from these other two classes of such proteins. HLL and HLP fusions to green fluorescent protein were localized to mitochondria. Ectopic expression of HLP complemented the hll mutant, indicating that HLP and HLL share redundant functions. We conclude that HLL and HLP encode L14 subunits of mitochondrial ribosomes. HLL mRNA was at significantly higher levels than HLP mRNA in pistils, with the opposite pattern in leaves. This differential expression can explain the confinement of effects of hll mutations to gynoecia and ovules. Our elucidation of the nature of HLL shows that metabolic defects can have specific effects on developmental patterning.
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Affiliation(s)
- D J Skinner
- Section of Molecular and Cellular Biology, University of California, 1 Shields Avenue, Davis, California 95616, USA
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10
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Skinner DJ, Baker SC, Meister RJ, Broadhvest J, Schneitz K, Gasser CS. The Arabidopsis HUELLENLOS gene, which is essential for normal ovule development, encodes a mitochondrial ribosomal protein. Plant Cell 2001; 13:2719-30. [PMID: 11752383 PMCID: PMC139484 DOI: 10.1105/tpc.010323] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2001] [Accepted: 09/17/2001] [Indexed: 05/18/2023]
Abstract
The HUELLENLOS (HLL) gene participates in patterning and growth of the Arabidopsis ovule. We have isolated the HLL gene and shown that it encodes a protein homologous to the L14 proteins of eubacterial ribosomes. The Arabidopsis genome also includes a highly similar gene, HUELLENLOS PARALOG (HLP), and genes for both cytosolic (L23) and chloroplast ribosome L14 proteins. Phylogenetic analysis shows that HLL and HLP differ significantly from these other two classes of such proteins. HLL and HLP fusions to green fluorescent protein were localized to mitochondria. Ectopic expression of HLP complemented the hll mutant, indicating that HLP and HLL share redundant functions. We conclude that HLL and HLP encode L14 subunits of mitochondrial ribosomes. HLL mRNA was at significantly higher levels than HLP mRNA in pistils, with the opposite pattern in leaves. This differential expression can explain the confinement of effects of hll mutations to gynoecia and ovules. Our elucidation of the nature of HLL shows that metabolic defects can have specific effects on developmental patterning.
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Affiliation(s)
- D J Skinner
- Section of Molecular and Cellular Biology, University of California, 1 Shields Avenue, Davis, California 95616, USA
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11
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Western TL, Burn J, Tan WL, Skinner DJ, Martin-McCaffrey L, Moffatt BA, Haughn GW. Isolation and characterization of mutants defective in seed coat mucilage secretory cell development in Arabidopsis. Plant Physiol 2001. [PMID: 11706181 DOI: 10.1104/pp.010410.upon] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
In Arabidopsis, fertilization induces the epidermal cells of the outer ovule integument to differentiate into a specialized seed coat cell type producing extracellular pectinaceous mucilage and a volcano-shaped secondary cell wall. Differentiation involves a regulated series of cytological events including growth, cytoplasmic rearrangement, mucilage synthesis, and secondary cell wall production. We have tested the potential of Arabidopsis seed coat epidermal cells as a model system for the genetic analysis of these processes. A screen for mutants defective in seed mucilage identified five novel genes (MUCILAGE-MODIFIED [MUM]1-5). The seed coat development of these mutants, and that of three previously identified ones (TRANSPARENT TESTA GLABRA1, GLABRA2, and APETALA2) were characterized. Our results show that the genes identified define several events in seed coat differentiation. Although APETALA2 is needed for differentiation of both outer layers of the seed coat, TRANSPARENT TESTA GLABRA1, GLABRA2, and MUM4 are required for complete mucilage synthesis and cytoplasmic rearrangement. MUM3 and MUM5 may be involved in the regulation of mucilage composition, whereas MUM1 and MUM2 appear to play novel roles in post-synthesis cell wall modifications necessary for mucilage extrusion.
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Affiliation(s)
- T L Western
- Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4
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Western TL, Burn J, Tan WL, Skinner DJ, Martin-McCaffrey L, Moffatt BA, Haughn GW. Isolation and characterization of mutants defective in seed coat mucilage secretory cell development in Arabidopsis. Plant Physiol 2001; 127:998-1011. [PMID: 11706181 DOI: 10.1104/pp.010410] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In Arabidopsis, fertilization induces the epidermal cells of the outer ovule integument to differentiate into a specialized seed coat cell type producing extracellular pectinaceous mucilage and a volcano-shaped secondary cell wall. Differentiation involves a regulated series of cytological events including growth, cytoplasmic rearrangement, mucilage synthesis, and secondary cell wall production. We have tested the potential of Arabidopsis seed coat epidermal cells as a model system for the genetic analysis of these processes. A screen for mutants defective in seed mucilage identified five novel genes (MUCILAGE-MODIFIED [MUM]1-5). The seed coat development of these mutants, and that of three previously identified ones (TRANSPARENT TESTA GLABRA1, GLABRA2, and APETALA2) were characterized. Our results show that the genes identified define several events in seed coat differentiation. Although APETALA2 is needed for differentiation of both outer layers of the seed coat, TRANSPARENT TESTA GLABRA1, GLABRA2, and MUM4 are required for complete mucilage synthesis and cytoplasmic rearrangement. MUM3 and MUM5 may be involved in the regulation of mucilage composition, whereas MUM1 and MUM2 appear to play novel roles in post-synthesis cell wall modifications necessary for mucilage extrusion.
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Affiliation(s)
- T L Western
- Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4
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13
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Abstract
OBJECTIVE To determine whether improvement in quality of semen over 4 consecutive days of electroejaculation in men with chronic spinal cord injury (SCI) was consistent with epididymal necrospermia. DESIGN Prospective study of a random sample of men with SCI. SETTING A southeastern Australian SCI management center in collaboration with the specialist andrology service of a university-based department of obstetrics and gynecology in a tertiary referral hospital. PATIENT(S) Nine men with chronic spinal cord injury. INTERVENTION(S) Semen samples were obtained by using electroejaculation, and testicular biopsy samples were obtained by using fine-needle tissue aspiration. MAIN OUTCOME MEASURE(S) Semen analysis was performed according to World Health Organization criteria. Testicular biopsy and electron microscopy were done by using standard techniques. RESULT(S) During up to 4 days of consecutive-day electroejaculation, sperm motility and viability in semen obtained from men with chronic SCI increased by an average of 23% on days 2 and 3. The severity of the degenerative changes and the numbers of spermatozoa affected on day 1 became less marked by day 4. The changes were not present in late spermatids obtained from testicular biopsies. CONCLUSION(S) The asthenospermia of chronic SCI is similar to epididymal necrospermia and can be improved by consecutive-day electroejaculation.
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Affiliation(s)
- C Mallidis
- Department of Obstetrics and Gynecology, University of Melbourne, Carlton, Victoria, Australia.
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Western TL, Skinner DJ, Haughn GW. Differentiation of mucilage secretory cells of the Arabidopsis seed coat. Plant Physiol 2000; 122:345-56. [PMID: 10677428 PMCID: PMC58872 DOI: 10.1104/pp.122.2.345] [Citation(s) in RCA: 211] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/1999] [Accepted: 10/17/1999] [Indexed: 05/17/2023]
Abstract
In some plant species, including Arabidopsis, fertilization induces the epidermal cells of the outer ovule integument to differentiate into a specialized seed coat cell type with a unique morphology and containing large quantities of polysaccharide mucilage (pectin). Such seed coat mucilage cells are necessary for neither viability nor germination under normal laboratory conditions. Thus, the Arabidopsis seed coat offers a unique system with which to use genetics to identify genes controlling cell morphogenesis and complex polysaccharide biosynthesis and secretion. As a first step in the application of this system, we have used microscopy to investigate the structure and differentiation of Arabidopsis seed coat mucilage cells, including cell morphogenesis and the synthesis, secretion, and extrusion of mucilage. During seed coat development in Arabidopsis, the epidermal cells of the outer ovule integument grow and differentiate into cells that produce large quantities of mucilage between the primary cell wall and plasma membrane. Concurrent with mucilage production, the cytoplasm is shaped into a column in the center of the cell. Following mucilage secretion the cytoplasmic column is surrounded by a secondary cell wall to form a structure known as the columella. Thus, differentiation of the seed coat mucilage cells involves a highly regulated series of events including growth, morphogenesis, mucilage biosynthesis and secretion, and secondary cell wall synthesis.
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Affiliation(s)
- T L Western
- Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia, Canada V6T 1Z4
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Abstract
In chronic spinal cord injury, semen obtained by assisted ejaculation is usually abnormal. We have assessed electroejaculation early after injury in seven patients. There were no adverse effects. Initial samples contained few or no spermatozoa but as patients emerged from spinal shock, semen improved and five had specimens cryopreserved. Thereafter sperm motility and viability decreased towards the pattern of chronic spinal cord injury by day 16. Cryopreservation was not possible in one patient with many medical complications and another who started electroejaculation 15 days after injury. Semen storage within the first 2 weeks after spinal cord injury is recommended for future fertility treatment.
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Affiliation(s)
- C Mallidis
- University of Melbourne Department of Obstetrics and Gynaecology, Australia
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Lim TC, Mallidis C, Hill ST, Skinner DJ, Carter PD, Brown DJ, Baker HW. A simple technique to prevent retrograde ejaculation during assisted ejaculation. Paraplegia 1994; 32:142-9. [PMID: 8008416 DOI: 10.1038/sc.1994.27] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The aim of this study was to develop a technique which would prevent retrograde ejaculation in chronic spinal cord injured (SCI) patients undergoing vibration and electroejaculation procedures. A balloon catheter was used to tamponade the bladder neck in 12 patients who underwent 100 assisted ejaculation procedures. Antegrade ejaculations were collected on all occasions with no incidences of urine contamination and no sperm were seen in post ejaculatory urine. Silicone catheters had minimal effects on sperm motility and viability. All lubricant gels were found to adversely affect sperm quality and were not used.
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Affiliation(s)
- T C Lim
- Spinal Injuries Unit, Austin Hospital, Heidelberg, Australia
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Thomas FC, Skinner DJ, Samagh BS. Evidence for bluetongue virus in Canada: 1976-1979. Can J Comp Med 1982; 46:350-3. [PMID: 6293686 PMCID: PMC1320291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Since the identification of approximately 1 400 bovine serological reactors to bluetongue virus in the Okanagan Valley of British Columbia in 1976, there has been no evidence of virus establishment in Canada. No clinical signs suggestive of bluetongue were observed. It was not possible to demonstrate viral activity at the time the seropositive animals were detected and subsequent serological testing supports the hypothesis that the virus has not become endemic or indeed survived in Canadian cattle populations. This combined with the dramatic reduction in prevalence of serological reactors in the years following the initial slaughter suggests that viral activity occurred in the Okanagan Valley prior to 1976 and disappeared. There has been no evidence for transmissions different from that expected of a classical arbovirus; that is, no evidence of "vertical" transmission.
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Skinner DJ, Izenstark JL. The technologist's role in roentgenographic and isotopic visualization of the pancreas. Radiol Technol 1967; 39:1-8. [PMID: 6044148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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