47 results on '"Sparkes I"'
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2. VIEWPOINT: Bleach it, switch it, bounce it, pull it: using lasers to reveal plant cell dynamics
- Author
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Sparkes, I. A., Graumann, K., Martinière, A., Schoberer, J., Wang, P., and Osterrieder, A.
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- 2011
- Full Text
- View/download PDF
3. Movement and Remodeling of the Endoplasmic Reticulum in Nondividing Cells of Tobacco Leaves
- Author
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Sparkes, I., Runions, J., Hawes, C., and Griffing, L.
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- 2009
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4. 2,4-Dichlorophenoxyacetic acid promotes S-nitrosylation and oxidation of actin affecting cytoskeleton and peroxisomal dynamics
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Rodríguez-Serrano, M., Pazmiño, D. M., Sparkes, I., Rochetti, A., Hawes, C., Romero-Puertas, M. C., and Sandalio, L. M.
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- 2014
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5. Bleach it, switch it, bounce it, pull it: using lasers to reveal plant cell dynamics
- Author
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Sparkes, I. A., Graumann, K., Martinière, A., Schoberer, J., Wang, P., and Osterrieder, A.
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- 2011
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6. VT16: Is the endoplasmic reticulum involved in peroxisome biogenesis in plants?
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Sparkes, I., Johnson, B., Evins, J., Kearns, A., Baker, A., and Haw, C.
- Published
- 2005
7. Plant VAP27 proteins: domain characterization, intracellular localization, and role in plant development.
- Author
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Wang, P, Richardson, C, Hawkins, T, Sparkes, I, Hawes, C, Hussey, P, Wang, P, Richardson, C, Hawkins, T, Sparkes, I, Hawes, C, and Hussey, P
- Abstract
• The endoplasmic reticulum (ER) is connected to the plasma membrane (PM) through the plant specific NETWORKED protein, NET3C, and phylogenetically conserved Vesicle-Associated Membrane Protein-Associated Proteins (VAPs). • Ten VAP homologues (VAP27-1 to 10) can be identified in the Arabidopsis genome and can be divided into three clades. Representative members from each clade have been tagged with fluorescent protein and expressed in Nicotiana benthamiana. • Proteins from clades one and three localised to the ER as well as to ER/PM contact sites (EPCS), whereas proteins from clade two are found only at the PM. Some of the VAP27 labelled EPCS localised to plasmodesmata, and we show that the mobility of VAP27 at the EPCS is influenced by the cell wall. EPCS closely associate with the cytoskeleton, but their structure is unaffected when the cytoskeleton is removed. • VAP27 labelled EPCS are found in most cell types in Arabidopsis with the exception of cells in early trichome development. Arabidopsis expressing VAP27-GFP fusions exhibit pleiotropic phenotypes including defects in root hair morphogenesis. A similar effect is also observed in plants expressing VAP27 RNAi. • Taken together these data indicate that VAP27 proteins used at the EPCS are essential for normal ER-cytoskeleton interaction and for plant development.
- Published
- 2016
8. Putting the squeeze on plasmodesmata- a role for reticulons in primary plasmodesmata formation
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Kriechbaumer, Verena, Frigerio, L, Sparkes, I, Hawes, Chris, Kriechbaumer, Verena, Frigerio, L, Sparkes, I, and Hawes, Chris
- Abstract
Primary plasmodesmata (PD) arise at cytokinesis when the new cell plate forms. During this process, fine strands of endoplasmic reticulum are laid down between enlarging Golgi-derived vesicles to form nascent PD, each pore containing a desmotubule, a membranous rod derived from the cortical ER. Little is known about the forces that model the ER during cell-plate formation. Here we show that members of the reticulon (RTNLB) family of ER-tubulating proteins may play a role in formation of the desmotubule. RTNLB3 and RTNLB6, two RTNLBs present in the PD proteome, are recruited to the cell plate at late telophase, when primary PD are formed, and remain associated with primary PD in the mature cell wall. Both RTNLBs showed significant co-localisation at PD with the viral movement protein of tobacco mosaic virus while super-resolution imaging (3D-SIM) of primary PD revealed the central desmotubule to be labelled by RTNLB6. FRAP studies showed that these RTNLBs are mobile at the edge of the developing cell plate, where new wall materials are being delivered, but significantly less mobile at its centre where PD are forming. A truncated RTNLB3, unable to constrict the ER, was not recruited to the cell plate at cytokinesis. We discuss the potential roles of RTNLBs in desmotubule formation
- Published
- 2015
9. The plant cytoskeleton, NET3C and VAP27 mediates the link between the plasma membrane and endoplasmic reticulum
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Wang, P, Hawkins, T, Richardson, C, Cummins, I, Deeks, M, Sparkes, I, Hawes, C, Hussey, P, Wang, P, Hawkins, T, Richardson, C, Cummins, I, Deeks, M, Sparkes, I, Hawes, C, and Hussey, P
- Abstract
The cortical endoplasmic reticulum (ER) network in plants is a highly dynamic structure and it contacts the plasma membrane (PM) at ER/PM anchor/contact sites. These sites are known to be essential for communication between the ER and PM for lipid transport, calcium influx and ER morphology in mammalian and fungal cells. The nature of these contact sites is unknown in plants [1, 2] and here we have identified a complex that forms this bridge. This complex includes (i) NET3C which belongs to a plant specific super-family (NET) of actin-binding proteins [3]. (ii) VAP27, a plant homologue of the yeast Scs2 ER/PM contact site protein [4, 5] and (iii) the actin and microtubule networks. We demonstrate that NET3C and VAP27 localise to punctae at the PM, that NET3C and VAP27 form homodimers/oligomers and together form complexes with actin and microtubules. We show that F-actin modulates the turnover of NET3C at these punctae and microtubules regulate the exchange of VAP27 at the same sites. Based on these data, we propose a model for the structure of the plant ER/PM contact sites.
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- 2014
10. 2,4-Dichlorophenoxyacetic acid promotes S-nitrosylation and oxidation of actin affecting cytoskeleton and peroxisomal dynamics
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Rodriguez-Serrano, M, Pazmino, D, Sparkes, I, Rocchetti, A, Hawes, C, Romero-Puertas, M, Sandalio, L, Rodriguez-Serrano, M, Pazmino, D, Sparkes, I, Rocchetti, A, Hawes, C, Romero-Puertas, M, and Sandalio, L
- Abstract
2,4-Dichlorophenoxyacetic acid (2,4-D) is a synthetic auxin used as a herbicide to control weeds in agriculture. A high concentration of 2,4-D promotes leaf epinasty and cell death. In this work, the molecular mechanisms involved in the toxicity of this herbicide are studied by analysing in Arabidopsis plants the accumulation of reactive oxygen species (ROS) and nitric oxide (NO), and their effect on cytoskeleton structure and peroxisome dynamics. 2,4-D (23 mM) promotes leaf epinasty, whereas this process was prevented by EDTA, which can reduce center dot OH accumulation. The analysis of ROS accumulation by confocal microscopy showed a 2,4-D-dependent increase in both H2O2 and O2 center dot(-), whereas total NO was not affected by the treatment. The herbicide promotes disturbances on the actin cytoskeleton structure as a result of post-translational modification of actin by oxidation and S-nitrosylation, which could disturb actin polymerization, as suggested by the reduction of the F-actin/G-actin ratio. These effects were reduced by EDTA, and the reduction of ROS production in Arabidopsis mutants deficient in xanthine dehydrogenase (Atxdh) gave rise to a reduction in actin oxidation. Also, 2,4-D alters the dynamics of the peroxisome, slowing the speed and shortening the distances by which these organelles are displaced. It is concluded that 2,4-D promotes oxidative and nitrosative stress, causing disturbances in the actin cytoskeleton, thereby affecting the dynamics of peroxisomes and some other organelles such as the mitochondria, with xanthine dehydrogenase being involved in ROS production under these conditions. These structural changes in turn appear to be responsible for the leaf epinasty.
- Published
- 2014
11. The plant endoplasmic reticulum: a cell-wide web
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Sparkes, I, Frigerio, L, Tolley, N, Hawes, Chris, Sparkes, I, Frigerio, L, Tolley, N, and Hawes, Chris
- Abstract
The ER (endoplasmic reticulum) in higher plants forms a pleomorphic web of membrane tubules and small cisternae that pervade the cytoplasm, but in particular form a polygonal network at the cortex of the cell which may be anchored to the plasma membrane. The network is associated with the actin cytoskeleton and demonstrates extensive mobility, which is most likely to be dependent on myosin motors. The ER is characterized by a number of domains which may be associated with specific functions such as protein storage, or with direct interaction with other organelles such as the Golgi apparatus, peroxisomes and plastids. In the present review we discuss the nature of the network, the role of shape-forming molecules such as the recently described reticulon family of proteins and the function of some of the major domains within the ER network.
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- 2009
12. The Ureide-Degrading Reactions of Purine Ring Catabolism Employ Three Amidohydrolases and One Aminohydrolase in Arabidopsis, Soybean, and Rice
- Author
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Werner, A. K., primary, Medina-Escobar, N., additional, Zulawski, M., additional, Sparkes, I. A., additional, Cao, F.-Q., additional, and Witte, C.-P., additional
- Published
- 2013
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13. Bleach it, switch it, bounce it, pull it: using lasers to reveal plant cell dynamics
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Sparkes, I. A., primary, Graumann, K., additional, Martiniere, A., additional, Schoberer, J., additional, Wang, P., additional, and Osterrieder, A., additional
- Published
- 2010
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14. In vivo imaging of Arabidopsis myosins: Class XI myosins perturb organelle movement
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Sparkes, I., primary, Teanby, N., additional, and Hawes, C., additional
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- 2008
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15. Role of reticulons on ER morphology and secretion
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Sparkes, I., primary, Tolley, N., additional, Hawes, C., additional, and Frigerio, L., additional
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- 2008
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16. Biochemical and molecular approaches to understanding protein import into peroxisomes
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Baker, A., primary, Charlton, W., additional, Johnson, B., additional, Lopez-Huertas, E., additional, Oh, J., additional, Sparkes, I., additional, and Thomas, J., additional
- Published
- 2000
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17. 'Faithful in adversity'.
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Sparkes I
- Abstract
Most nurses know of someone from whom they draw inspiration. For Ian Sparkes, this figure is Noel Chavasse, and here he recounts the extraordinary story of a clinician and First World War hero who was twice awarded the Victoria Cross before he was killed in action in 1917. [ABSTRACT FROM AUTHOR]
- Published
- 2006
18. Emergence and stability of endoplasmic reticulum network streaming in plant cells.
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Donovan GM, Lin C, Sparkes I, and Ashwin P
- Abstract
The endoplasmic reticulum (ER) network is highly complex and highly dynamic in its geometry, and undergoes extensive remodeling and bulk flow. It is known that the ER dynamics are driven by actin-myosin dependent processes. ER motion through the cytoplasm will cause forces on the cytoplasm that will induce flow. However, ER will also clearly be passively transported by the bulk cytoplasmic streaming. We take the complex ER network structure into account and propose a positive-feedback mechanism among myosin-like motors, actin alignment, ER network dynamics for the emergence of ER flow. Using this model, we demonstrate that ER streaming may be an emergent feature of this three-way interaction and that the persistent-point density may be a key driver of the emergence of ER streaming., Competing Interests: Declaration of competing interest No conflicts of interest to declare., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)
- Published
- 2024
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19. Using Optical Tweezers Combined with Total Internal Reflection Microscopy to Study Interactions Between the ER and Golgi in Plant Cells.
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Sparkes I, White RR, Bateman B, Botchway S, and Ward A
- Subjects
- Plant Cells, Golgi Apparatus, Biophysics, Microscopy, Optical Tweezers
- Abstract
Optical tweezers have been used to trap and micro-manipulate several biological specimens ranging from DNA, macromolecules, organelles, to single-celled organisms. Using a combination of the refraction and scattering of laser light from a focused laser beam, refractile objects are physically captured and can be moved within the surrounding media. The technique is routinely used to determine biophysical properties such as the forces exerted by motor proteins. Here, we describe how optical tweezers combined with total internal reflection fluorescence microscopy (TIRF) can be used to assess physical interactions between organelles, more specifically the ER and Golgi bodies in plant cells., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)
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- 2024
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20. ARP2/3 complex associates with peroxisomes to participate in pexophagy in plants.
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Martinek J, Cifrová P, Vosolsobě S, García-González J, Malínská K, Mauerová Z, Jelínková B, Krtková J, Sikorová L, Leaves I, Sparkes I, and Schwarzerová K
- Subjects
- Actin-Related Protein 2-3 Complex metabolism, Actins, Peroxisomes metabolism, Macroautophagy, Arabidopsis Proteins metabolism, Arabidopsis metabolism
- Abstract
Actin-related protein (ARP2/3) complex is a heteroheptameric protein complex, evolutionary conserved in all eukaryotic organisms. Its conserved role is based on the induction of actin polymerization at the interface between membranes and the cytoplasm. Plant ARP2/3 has been reported to participate in actin reorganization at the plasma membrane during polarized growth of trichomes and at the plasma membrane-endoplasmic reticulum contact sites. Here we demonstrate that individual plant subunits of ARP2/3 fused to fluorescent proteins form motile spot-like structures in the cytoplasm that are associated with peroxisomes in Arabidopsis and tobacco. ARP2/3 is found at the peroxisome periphery and contains the assembled ARP2/3 complex and the WAVE/SCAR complex subunit NAP1. This ARP2/3-positive peroxisomal domain colocalizes with the autophagosome and, under conditions that affect the autophagy, colocalization between ARP2/3 and the autophagosome increases. ARP2/3 subunits co-immunoprecipitate with ATG8f and peroxisome-associated ARP2/3 interact in vivo with the ATG8f marker. Since mutants lacking functional ARP2/3 complex have more peroxisomes than wild type, we suggest that ARP2/3 has a novel role in the process of peroxisome degradation by autophagy, called pexophagy., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)
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- 2023
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21. Chloroplasts alter their morphology and accumulate at the pathogen interface during infection by Phytophthora infestans.
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Savage Z, Duggan C, Toufexi A, Pandey P, Liang Y, Segretin ME, Yuen LH, Gaboriau DCA, Leary AY, Tumtas Y, Khandare V, Ward AD, Botchway SW, Bateman BC, Pan I, Schattat M, Sparkes I, and Bozkurt TO
- Subjects
- Actin Cytoskeleton metabolism, Actin Cytoskeleton microbiology, Bridged Bicyclo Compounds, Heterocyclic pharmacology, Chloroplasts drug effects, Chloroplasts immunology, Dinitrobenzenes pharmacology, Light, Microscopy, Confocal, Optical Tweezers, Plant Diseases microbiology, Plant Immunity, Plant Leaves drug effects, Plant Leaves microbiology, Plants, Genetically Modified, Reactive Oxygen Species metabolism, Sulfanilamides pharmacology, Thiazolidines pharmacology, Nicotiana drug effects, Nicotiana genetics, Nicotiana immunology, Chloroplasts microbiology, Host-Pathogen Interactions physiology, Phytophthora infestans pathogenicity, Nicotiana microbiology
- Abstract
Upon immune activation, chloroplasts switch off photosynthesis, produce antimicrobial compounds and associate with the nucleus through tubular extensions called stromules. Although it is well established that chloroplasts alter their position in response to light, little is known about the dynamics of chloroplast movement in response to pathogen attack. Here, we report that during infection with the Irish potato famine pathogen Phytophthora infestans, chloroplasts accumulate at the pathogen interface, associating with the specialized membrane that engulfs the pathogen haustorium. The chemical inhibition of actin polymerization reduces the accumulation of chloroplasts at pathogen haustoria, suggesting that this process is partially dependent on the actin cytoskeleton. However, chloroplast accumulation at haustoria does not necessarily rely on movement of the nucleus to this interface and is not affected by light conditions. Stromules are typically induced during infection, embracing haustoria and facilitating chloroplast interactions, to form dynamic organelle clusters. We found that infection-triggered stromule formation relies on BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1 (BAK1)-mediated surface immune signaling, whereas chloroplast repositioning towards haustoria does not. Consistent with the defense-related induction of stromules, effector-mediated suppression of BAK1-mediated immune signaling reduced stromule formation during infection. On the other hand, immune recognition of the same effector stimulated stromules, presumably via a different pathway. These findings implicate chloroplasts in a polarized response upon pathogen attack and point to more complex functions of these organelles in plant-pathogen interactions., (© 2021 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)
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- 2021
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22. It Started With a Kiss: Monitoring Organelle Interactions and Identifying Membrane Contact Site Components in Plants.
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Baillie AL, Falz AL, Müller-Schüssele SJ, and Sparkes I
- Abstract
Organelle movement and interaction are dynamic processes. Interpreting the functional role and mechanistic detail of interactions at membrane contact sites requires careful quantification of parameters such as duration, frequency, proximity, and surface area of contact, and identification of molecular components. We provide an overview of current methods used to quantify organelle interactions in plants and other organisms and propose novel applications of existing technologies to tackle this emerging topic in plant cell biology., (Copyright © 2020 Baillie, Falz, Müller-Schüssele and Sparkes.)
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- 2020
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23. Miro2 tethers the ER to mitochondria to promote mitochondrial fusion in tobacco leaf epidermal cells.
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White RR, Lin C, Leaves I, Castro IG, Metz J, Bateman BC, Botchway SW, Ward AD, Ashwin P, and Sparkes I
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- Arabidopsis Proteins genetics, Endoplasmic Reticulum genetics, Gene Expression Regulation, Plant, Microfilament Proteins genetics, Mitochondria genetics, Mutation, Plant Epidermis cytology, Plant Epidermis genetics, Plant Leaves genetics, Plants, Genetically Modified genetics, Signal Transduction, Nicotiana genetics, Arabidopsis Proteins metabolism, Endoplasmic Reticulum enzymology, Microfilament Proteins metabolism, Mitochondria enzymology, Mitochondrial Dynamics, Plant Epidermis enzymology, Plant Leaves enzymology, Plants, Genetically Modified enzymology, Nicotiana enzymology
- Abstract
Mitochondria are highly pleomorphic, undergoing rounds of fission and fusion. Mitochondria are essential for energy conversion, with fusion favouring higher energy demand. Unlike fission, the molecular components involved in mitochondrial fusion in plants are unknown. Here, we show a role for the GTPase Miro2 in mitochondria interaction with the ER and its impacts on mitochondria fusion and motility. Mutations in AtMiro2's GTPase domain indicate that the active variant results in larger, fewer mitochondria which are attached more readily to the ER when compared with the inactive variant. These results are contrary to those in metazoans where Miro predominantly controls mitochondrial motility, with additional GTPases affecting fusion. Synthetically controlling mitochondrial fusion rates could fundamentally change plant physiology by altering the energy status of the cell. Furthermore, altering tethering to the ER could have profound effects on subcellular communication through altering the exchange required for pathogen defence.
- Published
- 2020
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24. Lessons from optical tweezers: quantifying organelle interactions, dynamics and modelling subcellular events.
- Author
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Sparkes I
- Subjects
- Cell Membrane metabolism, Chloroplasts metabolism, Endoplasmic Reticulum metabolism, Golgi Apparatus metabolism, Peroxisomes metabolism, Plant Development, Optical Tweezers, Organelles physiology, Plant Cells
- Abstract
Optical tweezers enable users to physically trap organelles and move them laterally within the plant cell. Recent advances have highlighted physical interactions between functionally related organelle pairs, such as ER-Golgi and peroxisome-chloroplast, and have shown how organelle positioning affects plant growth. Quantification of these processes has provided insight into the force components which ultimately drive organelle movement and positioning in plant cells. Application of optical tweezers has therefore revolutionised our understanding of plant organelle dynamics., (Copyright © 2018 Elsevier Ltd. All rights reserved.)
- Published
- 2018
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25. Plant organelle dynamics: cytoskeletal control and membrane contact sites.
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Perico C and Sparkes I
- Subjects
- Actins metabolism, Models, Biological, Myosins metabolism, Cytoskeleton metabolism, Intracellular Membranes metabolism, Organelles metabolism
- Abstract
Contents Summary 381 I. Introduction 381 II. Basic movement characteristics 382 III. Actin and associated motors, myosins, play a primary role in plant organelle movement and positioning 382 IV. Mechanisms of myosin recruitment: a tightly regulated system? 384 V. Microtubules, associated motors and interplay with actin 386 VI. Role of organelle interactions: tales of tethers 387 VII. Summary model to describe organelle movement in higher plants 390 VIII. Why is organelle movement important? 390 IX. Conclusions and future perspectives 391 Acknowledgements 391 References 391 SUMMARY: Organelle movement and positioning are correlated with plant growth and development. Movement characteristics are seemingly erratic yet respond to external stimuli including pathogens and light. Given these clear correlations, we still do not understand the specific roles that movement plays in these processes. There are few exceptions including organelle inheritance during cell division and photorelocation of chloroplasts to prevent photodamage. The molecular and biophysical components that drive movement can be broken down into cytoskeletal components, motor proteins and tethers, which allow organelles to physically interact with one another. Our understanding of these components and concepts has exploded over the past decade, with recent technological advances allowing an even more in-depth profiling. Here, we provide an overview of the cytoskeletal and tethering components and discuss the mechanisms behind organelle movement in higher plants., (© 2018 The Authors. New Phytologist © 2018 New Phytologist Trust.)
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- 2018
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26. Modeling the Geometry and Dynamics of the Endoplasmic Reticulum Network.
- Author
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Lin C, Lemarchand L, Euler R, and Sparkes I
- Subjects
- Algorithms, Bridged Bicyclo Compounds, Heterocyclic pharmacology, Microscopy, Confocal, Plant Leaves cytology, Thiazolidines pharmacology, Nicotiana cytology, Computational Biology methods, Endoplasmic Reticulum drug effects, Endoplasmic Reticulum physiology, Endoplasmic Reticulum ultrastructure, Models, Biological
- Abstract
The endoplasmic reticulum (ER) is an intricate network that pervades the entire cortex of plant cells and its geometric shape undergoes drastic changes. This paper proposes a mathematical model to reconstruct geometric network dynamics by combining the node movements within the network and topological changes engendered by these nodes. The network topology in the model is determined by a modified optimization procedure from the work (Lemarchand, et al. 2014) which minimizes the total length taking into account both degree and angle constraints, beyond the conditions of connectedness and planarity. A novel feature for solving our optimization problem is the use of "lifted" angle constraints, which allows one to considerably reduce the solution runtimes. Using this optimization technique and a Langevin approach for the branching node movement, the simulated network dynamics represent the ER network dynamics observed under latrunculin B treated condition and recaptures features such as the appearance/disappearance of loops within the ER under the native condition. The proposed modeling approach allows quantitative comparison of networks between the model and experimental data based on topological changes induced by node dynamics. An increased temporal resolution of experimental data will allow a more detailed comparison of network dynamics using this modeling approach.
- Published
- 2018
- Full Text
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27. Using Optical Tweezers Combined with Total Internal Reflection Microscopy to Study Interactions Between the ER and Golgi in Plant Cells.
- Author
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Sparkes I, White RR, Coles B, Botchway SW, and Ward A
- Subjects
- Gene Expression, Genes, Reporter, Image Processing, Computer-Assisted methods, Molecular Imaging methods, Endoplasmic Reticulum metabolism, Golgi Apparatus metabolism, Microscopy methods, Optical Tweezers, Plant Cells metabolism, Signal Transduction
- Abstract
Optical tweezers have been used to trap and micromanipulate several biological specimens ranging from DNA, macromolecules, organelles to single celled organisms. Using a combination of the refraction and scattering of laser light from a focused laser beam, refractile objects are physically captured and can be moved within the surrounding media. The technique is routinely used to determine biophysical properties such as the forces exerted by motor proteins. Here, we describe how optical tweezers combined with total internal reflection fluorescence (TIRF) microscopy can be used to assess physical interactions between organelles, more specifically the ER and Golgi bodies in plant cells.
- Published
- 2018
- Full Text
- View/download PDF
28. From shaping organelles to signalling platforms: the emerging functions of plant ER-PM contact sites.
- Author
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Bayer EM, Sparkes I, Vanneste S, and Rosado A
- Subjects
- Cell Membrane metabolism, Cell Membrane microbiology, Endoplasmic Reticulum metabolism, Organelle Biogenesis, Plant Physiological Phenomena, Signal Transduction
- Abstract
The plant endoplasmic reticulum (ER) defines the biosynthetic site of lipids and proteins destined for secretion, but also contains important signal transduction and homeostasis components that regulate multiple hormonal and developmental responses. To achieve its various functions, the ER has a unique architecture, both reticulated and highly plastic, that facilitates the spatial-temporal segregation of biochemical reactions and the establishment of inter-organelle communication networks. At the cell cortex, the cortical ER (cER) anchors to and functionally couples with the PM through largely static structures known as ER-PM contact sites (EPCS). These spatially confined microdomains are emerging as critical regulators of the geometry of the cER network, and as highly specialized signalling hubs. In this review, we share recent insights into how EPCS regulate cER remodelling, and discuss the proposed roles for plant EPCS components in the integration of environmental and developmental signals at the cER-PM interface., (Copyright © 2017 Elsevier Ltd. All rights reserved.)
- Published
- 2017
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29. Modeling Endoplasmic Reticulum Network Maintenance in a Plant Cell.
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Lin C, White RR, Sparkes I, and Ashwin P
- Subjects
- Agrobacterium, Cytoplasmic Streaming physiology, Green Fluorescent Proteins genetics, Green Fluorescent Proteins metabolism, Luminescent Proteins genetics, Luminescent Proteins metabolism, Microscopy, Confocal, Plant Leaves cytology, Plant Leaves metabolism, Single-Cell Analysis, Nicotiana cytology, Nicotiana metabolism, Transformation, Genetic, Red Fluorescent Protein, Endoplasmic Reticulum metabolism, Models, Biological, Plant Cells metabolism
- Abstract
The endoplasmic reticulum (ER) in plant cells forms a highly dynamic network of complex geometry. ER network morphology and dynamics are influenced by a number of biophysical processes, including filament/tubule tension, viscous forces, Brownian diffusion, and interactions with many other organelles and cytoskeletal elements. Previous studies have indicated that ER networks can be thought of as constrained minimal-length networks acted on by a variety of forces that perturb and/or remodel the network. Here, we study two specific biophysical processes involved in remodeling. One is the dynamic relaxation process involving a combination of tubule tension and viscous forces. The other is the rapid creation of cross-connection tubules by direct or indirect interactions with cytoskeletal elements. These processes are able to remodel the ER network: the first reduces network length and complexity whereas the second increases both. Using live cell imaging of ER network dynamics in tobacco leaf epidermal cells, we examine these processes on ER network dynamics. Away from regions of cytoplasmic streaming, we suggest that the dynamic network structure is a balance between the two processes, and we build an integrative model of the two processes for network remodeling. This model produces quantitatively similar ER networks to those observed in experiments. We use the model to explore the effect of parameter variation on statistical properties of the ER network., (Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2017
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30. Plant ER geometry and dynamics: biophysical and cytoskeletal control during growth and biotic response.
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Griffing LR, Lin C, Perico C, White RR, and Sparkes I
- Subjects
- Models, Biological, Biophysical Phenomena, Cytoskeleton metabolism, Endoplasmic Reticulum metabolism, Plant Development, Plants metabolism
- Abstract
The endoplasmic reticulum (ER) is an intricate and dynamic network of membrane tubules and cisternae. In plant cells, the ER 'web' pervades the cortex and endoplasm and is continuous with adjacent cells as it passes through plasmodesmata. It is therefore the largest membranous organelle in plant cells. It performs essential functions including protein and lipid synthesis, and its morphology and movement are linked to cellular function. An emerging trend is that organelles can no longer be seen as discrete membrane-bound compartments, since they can physically interact and 'communicate' with one another. The ER may form a connecting central role in this process. This review tackles our current understanding and quantification of ER dynamics and how these change under a variety of biotic and developmental cues., Competing Interests: Compliance with ethical standard Conflict of interest The authors declare that they have no conflict of interest.
- Published
- 2017
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31. Plant VAP27 proteins: domain characterization, intracellular localization and role in plant development.
- Author
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Wang P, Richardson C, Hawkins TJ, Sparkes I, Hawes C, and Hussey PJ
- Subjects
- Amino Acid Sequence, Arabidopsis cytology, Arabidopsis growth & development, Arabidopsis Proteins genetics, Cell Membrane metabolism, Cytoskeleton metabolism, Endoplasmic Reticulum metabolism, Genes, Reporter, Membrane Proteins genetics, Membrane Proteins metabolism, Microtubules metabolism, Phylogeny, Plants, Genetically Modified, Plasmodesmata metabolism, Protein Domains, R-SNARE Proteins genetics, Sequence Alignment, Nicotiana genetics, Nicotiana growth & development, Nicotiana ultrastructure, Arabidopsis genetics, Arabidopsis Proteins metabolism, R-SNARE Proteins metabolism
- Abstract
The endoplasmic reticulum (ER) is connected to the plasma membrane (PM) through the plant-specific NETWORKED protein, NET3C, and phylogenetically conserved vesicle-associated membrane protein-associated proteins (VAPs). Ten VAP homologues (VAP27-1 to 27-10) can be identified in the Arabidopsis genome and can be divided into three clades. Representative members from each clade were tagged with fluorescent protein and expressed in Nicotiana benthamiana. Proteins from clades I and III localized to the ER as well as to ER/PM contact sites (EPCSs), whereas proteins from clade II were found only at the PM. Some of the VAP27-labelled EPCSs localized to plasmodesmata, and we show that the mobility of VAP27 at EPCSs is influenced by the cell wall. EPCSs closely associate with the cytoskeleton, but their structure is unaffected when the cytoskeleton is removed. VAP27-labelled EPCSs are found in most cell types in Arabidopsis, with the exception of cells in early trichome development. Arabidopsis plants expressing VAP27-GFP fusions exhibit pleiotropic phenotypes, including defects in root hair morphogenesis. A similar effect is also observed in plants expressing VAP27 RNAi. Taken together, these data indicate that VAP27 proteins used at EPCSs are essential for normal ER-cytoskeleton interaction and for plant development., (© 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.)
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- 2016
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32. Using Optical Tweezers to Characterize Physical Tethers at Membrane Contact Sites: Grab It, Pull It, Set It Free?
- Author
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Sparkes I
- Published
- 2016
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33. In Vivo Quantification of Peroxisome Tethering to Chloroplasts in Tobacco Epidermal Cells Using Optical Tweezers.
- Author
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Gao H, Metz J, Teanby NA, Ward AD, Botchway SW, Coles B, Pollard MR, and Sparkes I
- Subjects
- Actins chemistry, Actins metabolism, Chloroplasts metabolism, Peroxisomes metabolism, Plant Epidermis ultrastructure, Chloroplasts chemistry, Optical Tweezers, Peroxisomes chemistry, Plant Epidermis cytology, Nicotiana cytology
- Abstract
Peroxisomes are highly motile organelles that display a range of motions within a short time frame. In static snapshots, they can be juxtaposed to chloroplasts, which has led to the hypothesis that they are physically interacting. Here, using optical tweezers, we tested the dynamic physical interaction in vivo. Using near-infrared optical tweezers combined with TIRF microscopy, we were able to trap peroxisomes and approximate the forces involved in chloroplast association in vivo in tobacco (Nicotiana tabacum) and observed weaker tethering to additional unknown structures within the cell. We show that chloroplasts and peroxisomes are physically tethered through peroxules, a poorly described structure in plant cells. We suggest that peroxules have a novel role in maintaining peroxisome-organelle interactions in the dynamic environment. This could be important for fatty acid mobilization and photorespiration through the interaction with oil bodies and chloroplasts, highlighting a fundamentally important role for organelle interactions for essential biochemistry and physiological processes., (© 2016 American Society of Plant Biologists. All Rights Reserved.)
- Published
- 2016
- Full Text
- View/download PDF
34. Putting the Squeeze on Plasmodesmata: A Role for Reticulons in Primary Plasmodesmata Formation.
- Author
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Knox K, Wang P, Kriechbaumer V, Tilsner J, Frigerio L, Sparkes I, Hawes C, and Oparka K
- Subjects
- Arabidopsis Proteins genetics, Cell Line, Cell Wall genetics, Fluorescence Recovery After Photobleaching, Green Fluorescent Proteins genetics, Green Fluorescent Proteins metabolism, Membrane Proteins genetics, Membrane Proteins metabolism, Microscopy, Confocal, Plant Viral Movement Proteins genetics, Plant Viral Movement Proteins metabolism, Plants, Genetically Modified, Plasmodesmata genetics, Protein Transport, Nicotiana cytology, Nicotiana genetics, Nicotiana metabolism, Tobacco Mosaic Virus genetics, Tobacco Mosaic Virus metabolism, Arabidopsis Proteins metabolism, Cell Wall metabolism, Cytokinesis, Endoplasmic Reticulum metabolism, Plasmodesmata metabolism
- Abstract
Primary plasmodesmata (PD) arise at cytokinesis when the new cell plate forms. During this process, fine strands of endoplasmic reticulum (ER) are laid down between enlarging Golgi-derived vesicles to form nascent PD, each pore containing a desmotubule, a membranous rod derived from the cortical ER. Little is known about the forces that model the ER during cell plate formation. Here, we show that members of the reticulon (RTNLB) family of ER-tubulating proteins in Arabidopsis (Arabidopsis thaliana) may play a role in the formation of the desmotubule. RTNLB3 and RTNLB6, two RTNLBs present in the PD proteome, are recruited to the cell plate at late telophase, when primary PD are formed, and remain associated with primary PD in the mature cell wall. Both RTNLBs showed significant colocalization at PD with the viral movement protein of Tobacco mosaic virus, while superresolution imaging (three-dimensional structured illumination microscopy) of primary PD revealed the central desmotubule to be labeled by RTNLB6. Fluorescence recovery after photobleaching studies showed that these RTNLBs are mobile at the edge of the developing cell plate, where new wall materials are being delivered, but significantly less mobile at its center, where PD are forming. A truncated RTNLB3, unable to constrict the ER, was not recruited to the cell plate at cytokinesis. We discuss the potential roles of RTNLBs in desmotubule formation., (© 2015 American Society of Plant Biologists. All Rights Reserved.)
- Published
- 2015
- Full Text
- View/download PDF
35. Structure and dynamics of ER: minimal networks and biophysical constraints.
- Author
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Lin C, Zhang Y, Sparkes I, and Ashwin P
- Subjects
- Endoplasmic Reticulum chemistry, Endoplasmic Reticulum metabolism, Plant Cells ultrastructure, Nicotiana ultrastructure, Viscosity, Elasticity, Endoplasmic Reticulum ultrastructure, Molecular Dynamics Simulation
- Abstract
The endoplasmic reticulum (ER) in live cells is a highly mobile network whose structure dynamically changes on a number of timescales. The role of such drastic changes in any system is unclear, although there are correlations with ER function. A better understanding of the fundamental biophysical constraints on the system will allow biologists to determine the effects of molecular factors on ER dynamics. Previous studies have identified potential static elements that the ER may remodel around. Here, we use these structural elements to assess biophysical principles behind the network dynamics. By analyzing imaging data of tobacco leaf epidermal cells under two different conditions, i.e., native state (control) and latrunculin B (treated), we show that the geometric structure and dynamics of ER networks can be understood in terms of minimal networks. Our results show that the ER network is well modeled as a locally minimal-length network between the static elements that potentially anchor the ER to the cell cortex over longer timescales; this network is perturbed by a mixture of random and deterministic forces. The network need not have globally minimum length; we observe cases where the local topology may change dynamically between different Euclidean Steiner network topologies. The networks in the treated cells are easier to quantify, because they are less dynamic (the treatment suppresses actin dynamics), but the same general features are found in control cells. Using a Langevin approach, we model the dynamics of the nonpersistent nodes and use this to show that the images can be used to estimate both local viscoelastic behavior of the cytoplasm and filament tension in the ER network. This means we can explain several aspects of the ER geometry in terms of biophysical principles., (Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.)
- Published
- 2014
- Full Text
- View/download PDF
36. The plant cytoskeleton, NET3C, and VAP27 mediate the link between the plasma membrane and endoplasmic reticulum.
- Author
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Wang P, Hawkins TJ, Richardson C, Cummins I, Deeks MJ, Sparkes I, Hawes C, and Hussey PJ
- Subjects
- Actins metabolism, Arabidopsis genetics, Arabidopsis Proteins genetics, Cytoskeleton metabolism, Gene Expression Regulation, Plant, Membrane Proteins genetics, Microfilament Proteins genetics, Microtubules metabolism, R-SNARE Proteins genetics, Nicotiana genetics, Arabidopsis metabolism, Arabidopsis Proteins metabolism, Cell Membrane metabolism, Endoplasmic Reticulum metabolism, Membrane Proteins metabolism, Microfilament Proteins metabolism, R-SNARE Proteins metabolism, Nicotiana metabolism
- Abstract
The cortical endoplasmic reticulum (ER) network in plants is a highly dynamic structure, and it contacts the plasma membrane (PM) at ER-PM anchor/contact sites. These sites are known to be essential for communication between the ER and PM for lipid transport, calcium influx, and ER morphology in mammalian and fungal cells. The nature of these contact sites is unknown in plants, and here, we have identified a complex that forms this bridge. This complex includes (1) NET3C, which belongs to a plant-specific superfamily (NET) of actin-binding proteins, (2) VAP27, a plant homolog of the yeast Scs2 ER-PM contact site protein, and (3) the actin and microtubule networks. We demonstrate that NET3C and VAP27 localize to puncta at the PM and that NET3C and VAP27 form homodimers/oligomers and together form complexes with actin and microtubules. We show that F-actin modulates the turnover of NET3C at these puncta and microtubules regulate the exchange of VAP27 at the same sites. Based on these data, we propose a model for the structure of the plant ER-PM contact sites., (Copyright © 2014 Elsevier Ltd. All rights reserved.)
- Published
- 2014
- Full Text
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37. ER network dynamics are differentially controlled by myosins XI-K, XI-C, XI-E, XI-I, XI-1, and XI-2.
- Author
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Griffing LR, Gao HT, and Sparkes I
- Abstract
The endoplasmic reticulum (ER) of higher plants is a complex network of tubules and cisternae. Some of the tubules and cisternae are relatively persistent, while others are dynamically moving and remodeling through growth and shrinkage, cycles of tubule elongation and retraction, and cisternal expansion and diminution. Previous work showed that transient expression in tobacco leaves of the motor-less, truncated tail of myosin XI-K increases the relative area of both persistent cisternae and tubules in the ER. Likewise, transient expression of XI-K tail diminishes the movement of organelles such as Golgi and peroxisomes. To examine whether other class XI myosins are involved in the remodeling and movement of the ER, other myosin XIs implicated in organelle movement, XI-1 (MYA1),XI-2 (MYA2), XI-C, XI-E, XI-I, and one not, XI-A, were expressed as motor-less tail constructs and their effect on ER persistent structures determined. Here, we indicate a differential effect on ER dynamics whereby certain class XI myosins may have more influence over controlling cisternalization rather than tubulation.
- Published
- 2014
- Full Text
- View/download PDF
38. An Arabidopsis reticulon and the atlastin homologue RHD3-like2 act together in shaping the tubular endoplasmic reticulum.
- Author
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Lee H, Sparkes I, Gattolin S, Dzimitrowicz N, Roberts LM, Hawes C, and Frigerio L
- Subjects
- Arabidopsis Proteins chemistry, GTP-Binding Proteins chemistry, Golgi Apparatus metabolism, Immunoprecipitation, Mutant Proteins metabolism, Mutation genetics, Protein Binding, Protein Structure, Tertiary, Recombinant Fusion Proteins metabolism, Nicotiana metabolism, Arabidopsis metabolism, Arabidopsis Proteins metabolism, Endoplasmic Reticulum metabolism, GTP-Binding Proteins metabolism
- Abstract
The endoplasmic reticulum (ER) is a network of membrane sheets and tubules connected via three-way junctions. A family of proteins, the reticulons, are responsible for shaping the tubular ER. Reticulons interact with other tubule-forming proteins (Dp1 and Yop1p) and the GTPase atlastin. The Arabidopsis homologue of Dp1/Yop1p is HVA22. We show here that a seed-specific isoform of HVA22 labels the ER in tobacco (Nicotiana tabacum) cells but its overexpression does not alter ER morphology. The closest plant homologue of atlastin is RHD3. We show that RHD3-like 2 (RL2), the seed-specific isoform of RHD3, locates to the ER without affecting its shape or Golgi mobility. Expression of RL2-bearing mutations within its GTPase domain induces the formation of large ER strands, suggesting that a functional GTPase domain is important for the formation of three-way junctions. Coexpression of the reticulon RTNLB13 with RL2 resulted in a dramatic alteration of the ER network. This alteration did not depend on an active GTPase domain but required a functional reticulon, as no effect on ER morphology was seen when RL2 was coexpressed with a nonfunctional RTNLB13. RL2 and its GTPase mutants coimmunoprecipitate with RTNLB13. These results indicate that RL2 and RTNLB13 act together in modulating ER morphology., (© 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.)
- Published
- 2013
- Full Text
- View/download PDF
39. Fluorescent protein-based technologies: shedding new light on the plant endomembrane system.
- Author
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Sparkes I and Brandizzi F
- Subjects
- Endocytosis, Optical Tweezers, Organelles physiology, Plants genetics, Plants metabolism, Protein Interaction Mapping methods, Cell Membrane genetics, Cell Membrane metabolism, Green Fluorescent Proteins analysis, Plant Cells metabolism
- Abstract
Without doubt, GFP and spectral derivatives have revolutionized the way biologists approach their journey toward the discovery of how plant cells function. It is fascinating that in its early days GFP was used merely for localization studies, but as time progressed researchers successfully explored new avenues to push the power of GFP technology to reach new and exciting research frontiers. This has had a profound impact on the way we can now study complex and dynamic systems such as plant endomembranes. Here we briefly describe some of the approaches where GFP has revolutionized in vivo studies of protein distribution and dynamics and focus on two emerging approaches for the application of GFP technology in plant endomembranes, namely optical tweezers and forward genetics approaches, which are based either on the light or on genetic manipulation of secretory organelles to gain insights on the factors that control their activities and integrity., (© 2012 The Authors. The Plant Journal © 2012 Blackwell Publishing Ltd.)
- Published
- 2012
- Full Text
- View/download PDF
40. FrontiERs: movers and shapers of the higher plant cortical endoplasmic reticulum.
- Author
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Sparkes I, Hawes C, and Frigerio L
- Subjects
- Cytoskeleton metabolism, Golgi Apparatus metabolism, Movement, Plant Proteins metabolism, Endoplasmic Reticulum metabolism, Plants metabolism
- Abstract
The endoplasmic reticulum (ER) in higher plants performs many important functions, yet our understanding of how its intricate network shape and dynamics relate to function is very limited. Recent work has begun to unpick key molecular players in the generation of the pleomorphic, highly dynamic ER network structure that pervades the entire cytoplasm. ER movement is acto-myosin dependent. ER shape is dependent on RHD3 (Root Hair Defective 3) and a family of proteins called reticulons. The major challenge that lies ahead is understanding how factors that control ER shape and movement are regulated and how this relates to the numerous functions of the ER., (Copyright © 2011 Elsevier Ltd. All rights reserved.)
- Published
- 2011
- Full Text
- View/download PDF
41. Recent advances in understanding plant myosin function: life in the fast lane.
- Author
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Sparkes I
- Subjects
- Arabidopsis genetics, Arabidopsis growth & development, Arabidopsis Proteins genetics, Myosins genetics, Organelles genetics, Organelles metabolism, Arabidopsis metabolism, Arabidopsis Proteins metabolism, Myosins metabolism
- Abstract
Plant myosins are required for organelle movement, and a role in actin organization has recently come to light. Myosin mutants display several gross morphological phenotypes, the most severe being dwarfism and reduced fecundity, and there is a correlation between reduced organelle movement and morphological defects. This review aims to discuss recent findings in plants relating to the role of myosins in actin dynamics, development, and organelle movement, more specifically the endoplasmic reticulum (ER). One overarching theme is that there still appear to be more questions than answers relating to plant myosin function and regulation.
- Published
- 2011
- Full Text
- View/download PDF
42. Dynamic trafficking of wheat γ-gliadin and of its structural domains in tobacco cells, studied with fluorescent protein fusions.
- Author
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Francin-Allami M, Saumonneau A, Lavenant L, Bouder A, Sparkes I, Hawes C, and Popineau Y
- Subjects
- Actins metabolism, Brefeldin A pharmacology, Endoplasmic Reticulum drug effects, Endoplasmic Reticulum metabolism, Fluorescence, Immunoblotting, Plant Epidermis cytology, Plant Epidermis drug effects, Plant Epidermis metabolism, Plants, Genetically Modified, Protein Structure, Tertiary, Protein Transport drug effects, Subcellular Fractions metabolism, Nicotiana drug effects, Transformation, Genetic drug effects, Triticum drug effects, Vacuoles metabolism, Gliadin chemistry, Gliadin metabolism, Green Fluorescent Proteins metabolism, Recombinant Fusion Proteins metabolism, Nicotiana cytology, Nicotiana metabolism, Triticum metabolism
- Abstract
Prolamins, the main storage proteins of wheat seeds, are synthesized and retained in the endoplasmic reticulum (ER) of the endosperm cells, where they accumulate in protein bodies (PBs) and are then exported to the storage vacuole. The mechanisms leading to these events are unresolved. To investigate this unconventional trafficking pathway, wheat γ-gliadin and its isolated repeated N-terminal and cysteine-rich C-terminal domains were fused to fluorescent proteins and expressed in tobacco leaf epidermal cells. The results indicated that γ-gliadin and both isolated domains were able to be retained and accumulated as protein body-like structures (PBLS) in the ER, suggesting that tandem repeats are not the only sequence involved in γ-gliadin ER retention and PBLS formation. The high actin-dependent mobility of γ-gliadin PBLS is also reported, and it is demonstrated that most of them do not co-localize with Golgi body or pre-vacuolar compartment markers. Both γ-gliadin domains are found in the same PBLS when co-expressed, which is most probably due to their ability to interact with each other, as indicated by the yeast two-hybrid and FRET-FLIM experiments. Moreover, when stably expressed in BY-2 cells, green fluorescent protein (GFP) fusions to γ-gliadin and its isolated domains were retained in the ER for several days before being exported to the vacuole in a Golgi-dependent manner, and degraded, leading to the release of the GFP 'core'. Taken together, the results show that tobacco cells are a convenient model to study the atypical wheat prolamin trafficking with fluorescent protein fusions., (© 2011 The Author(s).)
- Published
- 2011
- Full Text
- View/download PDF
43. KMS1 and KMS2, two plant endoplasmic reticulum proteins involved in the early secretory pathway.
- Author
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Wang P, Hummel E, Osterrieder A, Meyer AJ, Frigerio L, Sparkes I, and Hawes C
- Subjects
- Amino Acid Sequence, Arabidopsis genetics, Arabidopsis Proteins genetics, Cloning, Molecular, Endoplasmic Reticulum metabolism, Gene Knockdown Techniques, Green Fluorescent Proteins metabolism, Hydrophobic and Hydrophilic Interactions, Molecular Sequence Data, Protein Transport, RNA Interference, Recombinant Fusion Proteins metabolism, Sequence Alignment, Sequence Analysis, Protein, Nicotiana metabolism, Nicotiana ultrastructure, Arabidopsis metabolism, Arabidopsis Proteins metabolism, Endoplasmic Reticulum ultrastructure, SNARE Proteins metabolism, Secretory Pathway, Nicotiana genetics
- Abstract
We have identified two endoplasmic reticulum (ER)-associated Arabidopsis proteins, KMS1 and KMS2, which are conserved among most species. Fluorescent protein fusions of KMS1 localised to the ER in plant cells, and over-expression induced the formation of a membrane structure, identified as ER whorls by electron microscopy. Hydrophobicity analysis suggested that KMS1 and KMS2 are integral membrane proteins bearing six transmembrane domains. Membrane protein topology was assessed by a redox-based topology assay (ReTA) with redox-sensitive GFP and confirmed by a protease protection assay. A major loop domain between transmembrane domains 2 and 3, plus the N- and C-termini were found on the cytosolic side of the ER. A C-terminal di(tri)-lysine motif is involved in retrieval of KMS1 and deletion led to a reduction of the GFP-KMS1 signal in the ER. Over-expression of KMS1/KMS2 truncations perturbed ER and Golgi morphology and similar effects were also seen when KMS1/KMS2 were knocked-down by RNA interference. Microscopy and biochemical experiments suggested that expression of KMS1/KMS2 truncations inhibited ER to Golgi protein transport., (© 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.)
- Published
- 2011
- Full Text
- View/download PDF
44. Transmembrane domain length is responsible for the ability of a plant reticulon to shape endoplasmic reticulum tubules in vivo.
- Author
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Tolley N, Sparkes I, Craddock CP, Eastmond PJ, Runions J, Hawes C, and Frigerio L
- Subjects
- Nicotiana chemistry, Nicotiana genetics, Arabidopsis chemistry, Arabidopsis Proteins chemistry, Endoplasmic Reticulum metabolism, Membrane Proteins chemistry, Microtubules metabolism
- Abstract
Reticulons are integral endoplasmic reticulum (ER) membrane proteins that have the ability to shape the ER into tubules. It has been hypothesized that their unusually long conserved hydrophobic regions cause reticulons to assume a wedge-like topology that induces membrane curvature. Here we provide proof of this hypothesis. When over-expressed, an Arabidopsis thaliana reticulon (RTNLB13) localized to, and induced constrictions in, cortical ER tubules. Ectopic expression of RTNLB13 was sufficient to induce ER tubulation in an Arabidopsis mutant (pah1 pah2) whose ER membrane is mostly present in a sheet-like form. By sequential shortening of the four transmembrane domains (TMDs) of RTNLB13, we show that the length of the transmembrane regions is directly correlated with the ability of RTNLB13 to induce membrane tubulation and to form low-mobility complexes within the ER membrane. We also show that full-length TMDs are necessary for the ability of RTNLB13 to reside in the ER membrane.
- Published
- 2010
- Full Text
- View/download PDF
45. Five Arabidopsis reticulon isoforms share endoplasmic reticulum location, topology, and membrane-shaping properties.
- Author
-
Sparkes I, Tolley N, Aller I, Svozil J, Osterrieder A, Botchway S, Mueller C, Frigerio L, and Hawes C
- Subjects
- Arabidopsis genetics, Arabidopsis Proteins genetics, Cloning, Molecular, Membrane Proteins genetics, Protein Isoforms chemistry, Protein Isoforms genetics, Protein Structure, Secondary, RNA, Plant genetics, Nicotiana chemistry, Nicotiana genetics, Arabidopsis chemistry, Arabidopsis Proteins chemistry, Endoplasmic Reticulum chemistry, Membrane Proteins chemistry
- Abstract
The cortical endoplasmic reticulum (ER) in tobacco (Nicotiana tabacum) epidermal cells is a network of tubules and cisternae undergoing dramatic rearrangements. Reticulons are integral membrane proteins involved in shaping ER tubules. Here, we characterized the localization, topology, effect, and interactions of five Arabidopsis thaliana reticulons (RTNs), isoforms 1-4 and 13, in the cortical ER. Our results indicate that RTNLB13 and RTNLB1-4 colocate to and constrict the tubular ER membrane. All five RTNs preferentially accumulate on ER tubules and are excluded from ER cisternae. All isoforms share the same transmembrane topology, with N and C termini facing the cytosol and four transmembrane domains. We show by Förster resonance energy transfer and fluorescence lifetime imaging microscopy that several RTNs have the capacity to interact with themselves and each other, and we suggest that oligomerization is responsible for their residence in the ER membrane. We also show that a complete reticulon homology domain is required for both RTN residence in high-curvature ER membranes and ER tubule constriction, yet it is not necessary for homotypic interactions.
- Published
- 2010
- Full Text
- View/download PDF
46. Peroxisome dynamics in Arabidopsis plants under oxidative stress induced by cadmium.
- Author
-
Rodríguez-Serrano M, Romero-Puertas MC, Sparkes I, Hawes C, del Río LA, and Sandalio LM
- Subjects
- Cell Growth Processes drug effects, Cytoskeleton drug effects, Fluorescent Antibody Technique, Microscopy, Confocal, Movement drug effects, Peroxisomes drug effects, Peroxisomes physiology, Peroxisomes ultrastructure, Plant Epidermis physiology, Plant Epidermis ultrastructure, Plant Leaves cytology, Reactive Oxygen Species metabolism, Arabidopsis physiology, Cadmium Chloride pharmacology, Oxidative Stress drug effects, Plant Epidermis drug effects
- Abstract
Peroxisomes are organelles with an essentially oxidative metabolism that are involved in various metabolic pathways such as fatty acid beta-oxidation, photorespiration, and metabolism of reactive oxygen species (ROS) and reactive nitrogen species. These organelles are highly dynamic but there is little information about the regulation of, and the effects of environment on, peroxisome movement. In this work a stable Arabidopsis line expressing the GFP-SKL peptide targeted to peroxisomes was characterized. Peroxisome-associated fluorescence was observed in all tissues, including leaves (mesophyll and epidermal cells, trichomes, and stomata) and roots. The dynamics of peroxisomes in epidermal cells was examined by confocal laser microscope, and various types of movement were observed. The speed of movement differed depending on the plant age. Treatment of plants with CdCl(2) (100 microM) produced a significant increase in speed, which was dependent on endogenous ROS and Ca(2+), but was not related to actin cytoskeleton modifications. In light of the results obtained, it is proposed that the increase in peroxisomal motility observed in Arabidopsis plants could be a cellular mechanism of protection against the Cd-imposed oxidative stress. Other possible roles for the enhanced peroxisome movement in plant cell physiology are discussed.
- Published
- 2009
- Full Text
- View/download PDF
47. The plant ER-Golgi interface.
- Author
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Hawes C, Osterrieder A, Hummel E, and Sparkes I
- Subjects
- COP-Coated Vesicles metabolism, COP-Coated Vesicles physiology, Plant Proteins metabolism, Plant Proteins physiology, Protein Transport, Secretory Pathway, Endoplasmic Reticulum metabolism, Endoplasmic Reticulum physiology, Golgi Apparatus metabolism, Golgi Apparatus physiology, Plant Physiological Phenomena
- Abstract
The interface between the endoplasmic reticulum (ER) and the Golgi apparatus is a critical junction in the secretory pathway mediating the transport of both soluble and membrane cargo between the two organelles. Such transport can be bidirectional and is mediated by coated membranes. In this review, we consider the organization and dynamics of this interface in plant cells, the putative structure of which has caused some controversy in the literature, and we speculate on the stages of Golgi biogenesis from the ER and the role of the Golgi and ER on each other's motility.
- Published
- 2008
- Full Text
- View/download PDF
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