1
|
Arnaud D, Deeks MJ, Smirnoff N. RBOHF activates stomatal immunity by modulating both reactive oxygen species and apoplastic pH dynamics in Arabidopsis. Plant J 2023; 116:404-415. [PMID: 37421599 PMCID: PMC10952706 DOI: 10.1111/tpj.16380] [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] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Revised: 06/28/2023] [Accepted: 07/04/2023] [Indexed: 07/10/2023]
Abstract
Stomatal defences are important for plants to prevent pathogen entry and further colonisation of leaves. Apoplastic reactive oxygen species (ROS) generated by NADPH oxidases and apoplastic peroxidases play an important role in activating stomatal closure upon perception of bacteria. However, downstream events, particularly the factors influencing cytosolic hydrogen peroxide (H2 O2 ) signatures in guard cells are poorly understood. We used the H2 O2 sensor roGFP2-Orp1 and a ROS-specific fluorescein probe to study intracellular oxidative events during stomatal immune response using Arabidopsis mutants involved in the apoplastic ROS burst. Surprisingly, the NADPH oxidase mutant rbohF showed over-oxidation of roGFP2-Orp1 by a pathogen-associated molecular pattern (PAMP) in guard cells. However, stomatal closure was not tightly correlated with high roGFP2-Orp1 oxidation. In contrast, RBOHF was necessary for PAMP-mediated ROS production measured by a fluorescein-based probe in guard cells. Unlike previous reports, the rbohF mutant, but not rbohD, was impaired in PAMP-triggered stomatal closure resulting in defects in stomatal defences against bacteria. Interestingly, RBOHF also participated in PAMP-induced apoplastic alkalinisation. The rbohF mutants were also partly impaired in H2 O2 -mediated stomatal closure at 100 μm while higher H2 O2 concentration up to 1 mm did not promote stomatal closure in wild-type plants. Our results provide novel insights on the interplay between apoplastic and cytosolic ROS dynamics and highlight the importance of RBOHF in plant immunity.
Collapse
Affiliation(s)
- Dominique Arnaud
- Biosciences, Faculty of Health and Life SciencesUniversity of ExeterExeterEX4 4QDUK
| | - Michael J. Deeks
- Biosciences, Faculty of Health and Life SciencesUniversity of ExeterExeterEX4 4QDUK
| | - Nicholas Smirnoff
- Biosciences, Faculty of Health and Life SciencesUniversity of ExeterExeterEX4 4QDUK
| |
Collapse
|
2
|
Child HT, Deeks MJ, Rudd JJ, Bates S. Comparison of the impact of two key fungal signalling pathways on Zymoseptoria tritici infection reveals divergent contribution to invasive growth through distinct regulation of infection-associated genes. Mol Plant Pathol 2023; 24:1220-1237. [PMID: 37306534 PMCID: PMC10502814 DOI: 10.1111/mpp.13365] [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] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 05/12/2023] [Accepted: 05/23/2023] [Indexed: 06/13/2023]
Abstract
The lifecycle of Zymoseptoria tritici requires a carefully regulated asymptomatic phase within the wheat leaf following penetration of the mesophyll via stomata. Here we compare the roles in this process of two key fungal signalling pathways, mutants of which were identified through forward genetics due to their avirulence on wheat. Whole-genome resequencing of avirulent Z. tritici T-DNA transformants identified disruptive mutations in ZtBCK1 from the kinase cascade of the cell wall integrity (CWI) pathway, and the adenylate cyclase gene ZtCYR1. Targeted deletion of these genes abolished the pathogenicity of the fungus and led to similar in vitro phenotypes to those associated with disruption of putative downstream kinases, both supporting previous studies and confirming the importance of these pathways in virulence. RNA sequencing was used to investigate the effect of ZtBCK1 and ZtCYR1 deletion on gene expression in both the pathogen and host during infection. ZtBCK1 was found to be required for the adaptation to the host environment, controlling expression of infection-associated secreted proteins, including known virulence factors. Meanwhile, ZtCYR1 is implicated in controlling the switch to necrotrophy, regulating expression of effectors associated with this transition. This represents the first study to compare the influence of CWI and cAMP signalling on in planta transcription of a fungal plant pathogen, providing insights into their differential regulation of candidate effectors during invasive growth.
Collapse
Affiliation(s)
| | | | - Jason J. Rudd
- Department of Protecting Crops and the EnvironmentRothamsted ResearchHarpendenUK
| | - Steven Bates
- Department of BiosciencesUniversity of ExeterExeterUK
| |
Collapse
|
3
|
Hembrow J, Deeks MJ, Richards DM. Automatic extraction of actin networks in plants. PLoS Comput Biol 2023; 19:e1011407. [PMID: 37647341 PMCID: PMC10497154 DOI: 10.1371/journal.pcbi.1011407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Revised: 09/12/2023] [Accepted: 08/01/2023] [Indexed: 09/01/2023] Open
Abstract
The actin cytoskeleton is essential in eukaryotes, not least in the plant kingdom where it plays key roles in cell expansion, cell division, environmental responses and pathogen defence. Yet, the precise structure-function relationships of properties of the actin network in plants are still to be unravelled, including details of how the network configuration depends upon cell type, tissue type and developmental stage. Part of the problem lies in the difficulty of extracting high-quality, quantitative measures of actin network features from microscopy data. To address this problem, we have developed DRAGoN, a novel image analysis algorithm that can automatically extract the actin network across a range of cell types, providing seventeen different quantitative measures that describe the network at a local level. Using this algorithm, we then studied a number of cases in Arabidopsis thaliana, including several different tissues, a variety of actin-affected mutants, and cells responding to powdery mildew. In many cases we found statistically-significant differences in actin network properties. In addition to these results, our algorithm is designed to be easily adaptable to other tissues, mutants and plants, and so will be a valuable asset for the study and future biological engineering of the actin cytoskeleton in globally-important crops.
Collapse
Affiliation(s)
- Jordan Hembrow
- Living Systems Institute and Department of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
| | - Michael J. Deeks
- Department of Biosciences, University of Exeter, Exeter, United Kingdom
| | - David M. Richards
- Living Systems Institute and Department of Physics and Astronomy, University of Exeter, Exeter, United Kingdom
| |
Collapse
|
4
|
Arnaud D, Deeks MJ, Smirnoff N. Organelle-targeted biosensors reveal distinct oxidative events during pattern-triggered immune responses. Plant Physiol 2023; 191:2551-2569. [PMID: 36582183 PMCID: PMC10069903 DOI: 10.1093/plphys/kiac603] [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] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 12/02/2022] [Accepted: 12/02/2022] [Indexed: 05/19/2023]
Abstract
Reactive oxygen species are produced in response to pathogens and pathogen-associated molecular patterns, as exemplified by the rapid extracellular oxidative burst dependent on the NADPH oxidase isoform RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD) in Arabidopsis (Arabidopsis thaliana). We used the H2O2 biosensor roGFP2-Orp1 and the glutathione redox state biosensor GRX1-roGFP2 targeted to various organelles to reveal unsuspected oxidative events during the pattern-triggered immune response to flagellin (flg22) and after inoculation with Pseudomonas syringae. roGFP2-Orp1 was oxidized in a biphasic manner 1 and 6 h after treatment, with a more intense and faster response in the cytosol compared to chloroplasts, mitochondria, and peroxisomes. Peroxisomal and cytosolic GRX1-roGFP2 were also oxidized in a biphasic manner. Interestingly, our results suggested that bacterial effectors partially suppress the second phase of roGFP2-Orp1 oxidation in the cytosol. Pharmacological and genetic analyses indicated that the pathogen-associated molecular pattern-induced cytosolic oxidation required the BRI1-ASSOCIATED RECEPTOR KINASE (BAK1) and BOTRYTIS-INDUCED KINASE 1 (BIK1) signaling components involved in the immune response but was largely independent of NADPH oxidases RBOHD and RESPIRATORY BURST OXIDASE HOMOLOG F (RBOHF) and apoplastic peroxidases peroxidase 33 (PRX33) and peroxidase 34 (PRX34). The initial apoplastic oxidative burst measured with luminol was followed by a second oxidation burst, both of which preceded the two waves of cytosolic oxidation. In contrast to the cytosolic oxidation, these bursts were RBOHD-dependent. Our results reveal complex oxidative sources and dynamics during the pattern-triggered immune response, including that cytosolic oxidation is largely independent of the preceding extracellular oxidation events.
Collapse
Affiliation(s)
- Dominique Arnaud
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Michael J Deeks
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK
| | | |
Collapse
|
5
|
Duckney P, Kroon JT, Dixon MR, Hawkins TJ, Deeks MJ, Hussey PJ. NETWORKED2-subfamily proteins regulate the cortical actin cytoskeleton of growing pollen tubes and polarised pollen tube growth. New Phytol 2021; 231:152-164. [PMID: 33864269 DOI: 10.1111/nph.17391] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Accepted: 03/29/2021] [Indexed: 06/12/2023]
Abstract
We have recently characterised NET2A as a pollen-specific actin-binding protein that binds F-actin at the plasma membrane of growing pollen tubes. However, the role of NET2 proteins in pollen development and fertilisation have yet to be elucidated. To further characterise the role of Arabidopsis NET2 proteins in pollen development and fertilisation, we analysed the subcellular localisation of NET2A over the course of pollen grain development and investigated the role of the NET2 family using net2 loss-of-function mutants. We observed NET2A to localise to the F-actin cytoskeleton in developing pollen grains as it underwent striking structural reorganisations at specific stages of development and during germination and pollen tube growth. Furthermore, net2 loss-of-function mutants exhibited striking morphological defects in the early stages of pollen tube growth, arising from frequent changes to pollen tube growth trajectory. We observed defects in the cortical actin cytoskeleton and actin-driven subcellular processes in net2 mutant pollen tubes. We demonstrate that NET2 proteins are essential for normal actin-driven pollen development highlighting an important role for the NET2 family members in regulating pollen tube growth during fertilisation.
Collapse
Affiliation(s)
- Patrick Duckney
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Johan T Kroon
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Martin R Dixon
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Timothy J Hawkins
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Michael J Deeks
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
- College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
| | - Patrick J Hussey
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| |
Collapse
|
6
|
Sassmann S, Rodrigues C, Milne SW, Nenninger A, Allwood E, Littlejohn GR, Talbot NJ, Soeller C, Davies B, Hussey PJ, Deeks MJ. An Immune-Responsive Cytoskeletal-Plasma Membrane Feedback Loop in Plants. Curr Biol 2018; 28:2136-2144.e7. [PMID: 29937351 PMCID: PMC6041470 DOI: 10.1016/j.cub.2018.05.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2017] [Revised: 03/21/2018] [Accepted: 05/04/2018] [Indexed: 11/20/2022]
Abstract
Cell wall appositions (CWAs) are produced reactively by the plant immune system to arrest microbial invasion through the local inversion of plant cell growth. This process requires the controlled invagination of the plasma membrane (PM) in coordination with the export of barrier material to the volume between the plant PM and cell wall. Plant actin dynamics are essential to this response, but it remains unclear how exocytosis and the cytoskeleton are linked in space and time to form functional CWAs. Here, we show that actin-dependent trafficking to immune response sites of Arabidopsis thaliana delivers membrane-integrated FORMIN4, which in turn contributes to local cytoskeletal dynamics. Total internal reflection fluorescence (TIRF) microscopy combined with controlled induction of FORMIN4-GFP expression reveals a dynamic population of vesicular bodies that accumulate to form clusters at the PM through an actin-dependent process. Deactivation of FORMIN4 and its close homologs partially compromises subsequent defense and alters filamentous actin (F-actin) distribution at mature CWAs. The localization of FORMIN4 is stable and segregated from the dynamic traffic of the endosomal network. Moreover, the tessellation of FORMIN4 at the PM with meso-domains of PEN3 reveals a fine spatial segregation of destinations for actin-dependent immunity cargo. Together, our data suggest a model where FORMIN4 is a spatial feedback element in a multi-layered, temporally defined sequence of cytoskeletal response. This positional feedback makes a significant contribution to the distribution of actin filaments at the dynamic CWA boundary and to the outcomes of pre-invasion defense.
Collapse
Affiliation(s)
- Stefan Sassmann
- Biosciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
| | | | - Stephen W Milne
- Biosciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
| | - Anja Nenninger
- Biosciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
| | - Ellen Allwood
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK
| | | | | | - Christian Soeller
- Physics and Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
| | - Brendan Davies
- School of Biology, University of Leeds, Miall Building, Leeds LS2 9JT, UK
| | - Patrick J Hussey
- Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK.
| | - Michael J Deeks
- Biosciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK; Department of Biosciences, Durham University, South Road, Durham DH1 3LE, UK.
| |
Collapse
|
7
|
Duckney P, Deeks MJ, Dixon MR, Kroon J, Hawkins TJ, Hussey PJ. Actin-membrane interactions mediated by NETWORKED2 in Arabidopsis pollen tubes through associations with Pollen Receptor-Like Kinase 4 and 5. New Phytol 2017; 216:1170-1180. [PMID: 28940405 DOI: 10.1111/nph.14745] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2017] [Accepted: 07/11/2017] [Indexed: 06/07/2023]
Abstract
During fertilization, Pollen Receptor-Like Kinases (PRKs) control pollen tube growth through the pistil in response to extracellular signals, and regulate the actin cytoskeleton at the tube apex to drive tip growth. We investigated a novel link between membrane-integral PRKs and the actin cytoskeleton, mediated through interactions between PRKs and NET2A; a pollen-specific member of the NETWORKED superfamily of actin-binding proteins. We characterize NET2A as a novel actin-associated protein that localizes to punctae at the plasma membrane of the pollen tube shank, which are stably associated with cortical longitudinal actin cables. NET2A was demonstrated to interact specifically with PRK4 and PRK5 in Nicotiana benthamiana transient expression assays, and associated at discreet foci at the shank membrane of Arabidopsis pollen tubes. Our data indicate that NET2A is recruited to the plasma membrane by PRK4 and PRK5, and that PRK kinase activity is important in facilitating its interaction with NET2A. We conclude that NET2A-PRK interactions mediate discreet sites of stable interactions between the cortical longitudinal actin cables and plasma membrane in the shank region of growing pollen tubes, which we have termed Actin-Membrane Contact Sites (AMCSs). Interactions between PRKs and NET2A implicate a role for NET2A in signal transduction to the actin cytoskeleton during fertilization.
Collapse
Affiliation(s)
- Patrick Duckney
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Michael J Deeks
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
- College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
| | - Martin R Dixon
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Johan Kroon
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Timothy J Hawkins
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| | - Patrick J Hussey
- Department of Biosciences, Durham University, South Road, Durham, DH1 3LE, UK
| |
Collapse
|
8
|
Isner JC, Xu Z, Costa JM, Monnet F, Batstone T, Ou X, Deeks MJ, Genty B, Jiang K, Hetherington AM. Actin filament reorganisation controlled by the SCAR/WAVE complex mediates stomatal response to darkness. New Phytol 2017; 215:1059-1067. [PMID: 28636198 PMCID: PMC5519931 DOI: 10.1111/nph.14655] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 04/25/2017] [Indexed: 05/20/2023]
Abstract
Stomata respond to darkness by closing to prevent excessive water loss during the night. Although the reorganisation of actin filaments during stomatal closure is documented, the underlying mechanisms responsible for dark-induced cytoskeletal arrangement remain largely unknown. We used genetic, physiological and cell biological approaches to show that reorganisation of the actin cytoskeleton is required for dark-induced stomatal closure. The opal5 mutant does not close in response to darkness but exhibits wild-type (WT) behaviour when exposed to abscisic acid (ABA) or CaCl2 . The mutation was mapped to At5g18410, encoding the PIR/SRA1/KLK subunit of the ArabidopsisSCAR/WAVE complex. Stomata of an independent allele of the PIR gene (Atpir-1) showed reduced sensitivity to darkness and F1 progenies of the cross between opal5 and Atpir-1 displayed distorted leaf trichomes, suggesting that the two mutants are allelic. Darkness induced changes in the extent of actin filament bundling in WT. These were abolished in opal5. Disruption of filamentous actin using latrunculin B or cytochalasin D restored wild-type stomatal sensitivity to darkness in opal5. Our findings suggest that the stomatal response to darkness is mediated by reorganisation of guard cell actin filaments, a process that is finely tuned by the conserved SCAR/WAVE-Arp2/3 actin regulatory module.
Collapse
Affiliation(s)
- Jean-Charles Isner
- School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK
| | - Zaoxu Xu
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang Province, 310058, China
| | - Joaquim Miguel Costa
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Centre National de la Recherche Scientifique UMR 7265, Université Aix-Marseille, Biologie Végétale et Microbiologie Environnementales, Saint-Paul-lez-Durance, 13108, France
| | - Fabien Monnet
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Centre National de la Recherche Scientifique UMR 7265, Université Aix-Marseille, Biologie Végétale et Microbiologie Environnementales, Saint-Paul-lez-Durance, 13108, France
| | - Thomas Batstone
- School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK
| | - Xiaobin Ou
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang Province, 310058, China
| | - Michael J Deeks
- Department of Biosciences, University of Exeter, Exeter, EX4 4QD, UK
| | - Bernard Genty
- Commissariat à l'Energie Atomique et aux Energies Alternatives, Centre National de la Recherche Scientifique UMR 7265, Université Aix-Marseille, Biologie Végétale et Microbiologie Environnementales, Saint-Paul-lez-Durance, 13108, France
| | - Kun Jiang
- College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang Province, 310058, China
| | - Alistair M Hetherington
- School of Biological Sciences, University of Bristol, Life Sciences Building, 24 Tyndall Avenue, Bristol, BS8 1TQ, UK
| |
Collapse
|
9
|
Fricker MD, Moger J, Littlejohn GR, Deeks MJ. Making microscopy count: quantitative light microscopy of dynamic processes in living plants. J Microsc 2016; 263:181-91. [PMID: 27145353 DOI: 10.1111/jmi.12403] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2015] [Revised: 01/31/2016] [Accepted: 02/16/2016] [Indexed: 12/18/2022]
Abstract
Cell theory has officially reached 350 years of age as the first use of the word 'cell' in a biological context can be traced to a description of plant material by Robert Hooke in his historic publication 'Micrographia: or some physiological definitions of minute bodies'. The 2015 Royal Microscopical Society Botanical Microscopy meeting was a celebration of the streams of investigation initiated by Hooke to understand at the subcellular scale how plant cell function and form arises. Much of the work presented, and Honorary Fellowships awarded, reflected the advanced application of bioimaging informatics to extract quantitative data from micrographs that reveal dynamic molecular processes driving cell growth and physiology. The field has progressed from collecting many pixels in multiple modes to associating these measurements with objects or features that are meaningful biologically. The additional complexity involves object identification that draws on a different type of expertise from computer science and statistics that is often impenetrable to biologists. There are many useful tools and approaches being developed, but we now need more interdisciplinary exchange to use them effectively. In this review we show how this quiet revolution has provided tools available to any personal computer user. We also discuss the oft-neglected issue of quantifying algorithm robustness and the exciting possibilities offered through the integration of physiological information generated by biosensors with object detection and tracking.
Collapse
Affiliation(s)
- Mark D Fricker
- Department of Plant Sciences, University of Oxford, Oxford, U.K
| | - Julian Moger
- Department of Physics, University of Exeter, Exeter, Devon, U.K
| | | | - Michael J Deeks
- Department of Biosciences, University of Exeter, Exeter, Devon, U.K
| |
Collapse
|
10
|
Abstract
Exocytosis involves the fusion of intracellular secretory vesicles with the plasma membrane, thereby delivering integral membrane proteins to the cell surface and releasing material into the extracellular space. Importantly, exocytosis also provides a source of lipid moieties for membrane extension. The tethering of the secretory vesicle before docking and fusion with the plasma membrane is mediated by the exocyst complex, an evolutionary conserved octameric complex of proteins. Recent findings indicate that the exocyst complex also takes part in other intra-cellular processes besides secretion. These various functions seem to converge toward defining a direction of membrane growth in a range of systems from fungi to plants and from neurons to cilia. In this review we summarize the current knowledge of exocyst function in cell polarity, signaling and cell-cell communication and discuss implications for plant and animal health and disease.
Collapse
Affiliation(s)
| | - Michael J Deeks
- Biosciences, College of Life and Environmental Sciences, University of Exeter Exeter, UK
| | - Connor G Horton
- Biosciences, College of Life and Environmental Sciences, University of Exeter Exeter, UK
| | - Helen R Dawe
- Biosciences, College of Life and Environmental Sciences, University of Exeter Exeter, UK
| | - Isabelle Jourdain
- Biosciences, College of Life and Environmental Sciences, University of Exeter Exeter, UK
| |
Collapse
|
11
|
Nelson CJ, Duckney P, Hawkins TJ, Deeks MJ, Laissue PP, Hussey PJ, Obara B. Blobs and curves: object-based colocalisation for plant cells. Funct Plant Biol 2015; 42:471-485. [PMID: 32480693 DOI: 10.1071/fp14047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Accepted: 07/21/2014] [Indexed: 06/11/2023]
Abstract
Blobs and curves occur everywhere in plant bioimaging: from signals of fluorescence-labelled proteins, through cytoskeletal structures, nuclei staining and cell extensions such as root hairs. Here we look at the problem of colocalisation of blobs with blobs (protein-protein colocalisation) and blobs with curves (organelle-cytoskeleton colocalisation). This article demonstrates a clear quantitative alternative to pixel-based colocalisation methods and, using object-based methods, can quantify not only the level of colocalisation but also the distance between objects. Included in this report are computational algorithms, biological experiments and guidance for those looking to increase their use of computationally-based and quantified analysis of bioimages.
Collapse
Affiliation(s)
- Carl J Nelson
- School of Engineering and Computing Sciences, Durham University, Durham DH13LE, UK
| | - Patrick Duckney
- School of Biological and Biomedical Sciences, Durham University, Durham DH13LE, UK
| | - Timothy J Hawkins
- School of Biological and Biomedical Sciences, Durham University, Durham DH13LE, UK
| | - Michael J Deeks
- College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4SB, UK
| | - P Philippe Laissue
- School of Biological Sciences, University of Essex, Colchester CO4 3SQ, UK
| | - Patrick J Hussey
- School of Biological and Biomedical Sciences, Durham University, Durham DH13LE, UK
| | - Boguslaw Obara
- School of Engineering and Computing Sciences, Durham University, Durham DH13LE, UK
| |
Collapse
|
12
|
Wang P, Hawkins TJ, Richardson C, Cummins I, Deeks MJ, Sparkes I, Hawes C, Hussey PJ. The plant cytoskeleton, NET3C, and VAP27 mediate the link between the plasma membrane and endoplasmic reticulum. Curr Biol 2014; 24:1397-1405. [PMID: 24909329 DOI: 10.1016/j.cub.2014.05.003] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 04/04/2014] [Accepted: 05/02/2014] [Indexed: 02/03/2023]
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.
Collapse
Affiliation(s)
- Pengwei Wang
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| | - Timothy J Hawkins
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| | - Christine Richardson
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| | - Ian Cummins
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| | - Michael J Deeks
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| | - Imogen Sparkes
- Department of Biological and Medical Sciences, Oxford Brookes University, Gipsy Lane, Headington, Oxford OX3 0BP, UK
| | - Chris Hawes
- Department of Biological and Medical Sciences, Oxford Brookes University, Gipsy Lane, Headington, Oxford OX3 0BP, UK
| | - Patrick J Hussey
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK.
| |
Collapse
|
13
|
Hawkins TJ, Deeks MJ, Wang P, Hussey PJ. The evolution of the actin binding NET superfamily. Front Plant Sci 2014; 5:254. [PMID: 24926301 PMCID: PMC4046492 DOI: 10.3389/fpls.2014.00254] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 05/19/2014] [Indexed: 05/19/2023]
Abstract
The Arabidopsis Networked (NET) superfamily are plant-specific actin binding proteins which specifically label different membrane compartments and identify specialized sites of interaction between actin and membranes unique to plants. There are 13 members of the superfamily in Arabidopsis, which group into four distinct clades or families. NET homologs are absent from the genomes of metazoa and fungi; furthermore, in plantae, NET sequences are also absent from the genome of mosses and more ancient extant plant clades. A single family of the NET proteins is found encoded in the club moss genome, an extant species of the earliest vascular plants. Gymnosperms have examples from families 4 and 3, with a hybrid form of NET1 and 2 which shows characteristics of both NET1 and NET2. In addition to NET3 and 4 families, the NET1 and pollen-expressed NET2 families are found only as independent sequences in Angiosperms. This is consistent with the divergence of reproductive actin. The four families are conserved across Monocots and Eudicots, with the numbers of members of each clade expanding at this point, due, in part, to regions of genome duplication. Since the emergence of the NET superfamily at the dawn of vascular plants, they have continued to develop and diversify in a manner which has mirrored the divergence and increasing complexity of land-plant species.
Collapse
Affiliation(s)
- Timothy J. Hawkins
- School of Biological and Biomedical Sciences, Durham UniversityDurham, UK
| | - Michael J. Deeks
- College of Life and Environmental Sciences, University of ExeterExeter, UK
| | - Pengwei Wang
- School of Biological and Biomedical Sciences, Durham UniversityDurham, UK
| | - Patrick J. Hussey
- School of Biological and Biomedical Sciences, Durham UniversityDurham, UK
- *Correspondence: Patrick J. Hussey, School of Biological and Biomedical Sciences, Durham University, South Road, Durham, DH1 3LE, UK e-mail:
| |
Collapse
|
14
|
Deeks MJ, Calcutt JR, Ingle EKS, Hawkins TJ, Chapman S, Richardson AC, Mentlak DA, Dixon MR, Cartwright F, Smertenko AP, Oparka K, Hussey PJ. A superfamily of actin-binding proteins at the actin-membrane nexus of higher plants. Curr Biol 2012; 22:1595-600. [PMID: 22840520 DOI: 10.1016/j.cub.2012.06.041] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Revised: 05/21/2012] [Accepted: 06/12/2012] [Indexed: 11/24/2022]
Abstract
Complex animals use a wide variety of adaptor proteins to produce specialized sites of interaction between actin and membranes. Plants do not have these protein families, yet actin-membrane interactions within plant cells are critical for the positioning of subcellular compartments, for coordinating intercellular communication, and for membrane deformation. Novel factors are therefore likely to provide interfaces at actin-membrane contacts in plants, but their identity has remained obscure. Here we identify the plant-specific Networked (NET) superfamily of actin-binding proteins, members of which localize to the actin cytoskeleton and specify different membrane compartments. The founding member of the NET superfamily, NET1A, is anchored at the plasma membrane and predominates at cell junctions, the plasmodesmata. NET1A binds directly to actin filaments via a novel actin-binding domain that defines a superfamily of thirteen Arabidopsis proteins divided into four distinct phylogenetic clades. Members of other clades identify interactions at the tonoplast, nuclear membrane, and pollen tube plasma membrane, emphasizing the role of this superfamily in mediating actin-membrane interactions.
Collapse
Affiliation(s)
- Michael J Deeks
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
15
|
Tóth R, Gerding-Reimers C, Deeks MJ, Menninger S, Gallegos RM, Tonaco IAN, Hübel K, Hussey PJ, Waldmann H, Coupland G. Prieurianin/endosidin 1 is an actin-stabilizing small molecule identified from a chemical genetic screen for circadian clock effectors in Arabidopsis thaliana. Plant J 2012; 71:338-52. [PMID: 22409627 DOI: 10.1111/j.1365-313x.2012.04991.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Chemical modulators are powerful tools to investigate biological processes. To identify circadian clock effectors, we screened a natural product library in the model plant Arabidopsis thaliana. Two compounds, prieurianin (Pri) and prieurianin acetate, were identified as causing a shorter circadian period. Recently, Pri was independently identified as a vesicle trafficking inhibitor and re-named endosidin 1 (ES1). Here we show that Pri primarily affects actin filament flexibility in vivo, later resulting in reduced severing and filament depolymerization. This stabilization of the actin cytoskeleton subsequently causes changes in vesicle trafficking. Pri also affected microfilaments in mammalian cells, indicating that its target is highly conserved; however, it did not alter actin dynamics in vitro, suggesting that its activity requires the presence of actin-associated proteins. Furthermore, well-characterized actin inhibitors shortened the period length of the Arabidopsis clock in a similar way to Pri, supporting the idea that Pri affects rhythms by altering the actin network. We conclude that actin-associated processes influence the circadian system in a light-dependent manner, but their disruption does not abolish rhythmicity. In summary, we propose that the primary effect of Pri is to stabilize the actin cytoskeleton system, thereby affecting endosome trafficking. Pri appears to stabilize actin filaments by a different mechanism from previously described inhibitors, and will be a useful tool to study actin-related cellular processes.
Collapse
Affiliation(s)
- Réka Tóth
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Jiang K, Sorefan K, Deeks MJ, Bevan MW, Hussey PJ, Hetherington AM. The ARP2/3 complex mediates guard cell actin reorganization and stomatal movement in Arabidopsis. Plant Cell 2012; 24:2031-40. [PMID: 22570440 PMCID: PMC3442585 DOI: 10.1105/tpc.112.096263] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2012] [Revised: 03/29/2012] [Accepted: 04/16/2012] [Indexed: 05/19/2023]
Abstract
Guard cell actin reorganization has been observed in stomatal responses to a wide array of stimuli. However, how the guard cell signaling machinery regulates actin dynamics is poorly understood. Here, we report the identification of an allele of the Arabidopsis thaliana ACTIN-RELATED PROTEIN C2/DISTORTED TRICHOMES2 (ARPC2) locus (encoding the ARPC2 subunit of the ARP2/3 complex) designated high sugar response3 (hsr3). The hsr3 mutant showed increased transpirational water loss that was mainly due to a lesion in stomatal regulation. Stomatal bioassay analyses revealed that guard cell sensitivity to external stimuli, such as abscisic acid (ABA), CaCl(2), and light/dark transition, was reduced or abolished in hsr3. Analysis of a nonallelic mutant of the ARP2/3 complex suggested no pleiotropic effect of ARPC2 beyond its function in the complex in regard to stomatal regulation. When treated with ABA, guard cell actin filaments underwent fast disruption in wild-type plants, whereas those in hsr3 remained largely bundled. The ABA insensitivity phenotype of hsr3 was rescued by cytochalasin D treatment, suggesting that the aberrant stomatal response was a consequence of bundled actin filaments. Our work indicates that regulation of actin reassembly through ARP2/3 complex activity is crucial for stomatal regulation.
Collapse
Affiliation(s)
- Kun Jiang
- School of Biological Sciences, University of Bristol, Bristol BS8 1UG, United Kingdom
| | - Karim Sorefan
- Cell and Developmental Biology Department, John Innes Centre, Norwich, Norfolk NR4 7UH, United Kingdom
| | - Michael J. Deeks
- School of Biological and Biomedical Sciences, University of Durham, Durham DH1 3LE, United Kingdom
| | - Michael W. Bevan
- Cell and Developmental Biology Department, John Innes Centre, Norwich, Norfolk NR4 7UH, United Kingdom
| | - Patrick J. Hussey
- School of Biological and Biomedical Sciences, University of Durham, Durham DH1 3LE, United Kingdom
| | | |
Collapse
|
17
|
Liu J, Piette BMAG, Deeks MJ, Franklin-Tong VE, Hussey PJ. A compartmental model analysis of integrative and self-regulatory ion dynamics in pollen tube growth. PLoS One 2010; 5:e13157. [PMID: 20949135 PMCID: PMC2950844 DOI: 10.1371/journal.pone.0013157] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 09/14/2010] [Indexed: 11/19/2022] Open
Abstract
Sexual reproduction in higher plants relies upon the polarised growth of pollen tubes. The growth-site at the pollen tube tip responds to signalling processes to successfully steer the tube to an ovule. Essential features of pollen tube growth are polarisation of ion fluxes, intracellular ion gradients, and oscillating dynamics. However, little is known about how these features are generated and how they are causally related. We propose that ion dynamics in biological systems should be studied in an integrative and self-regulatory way. Here we have developed a two-compartment model by integrating major ion transporters at both the tip and shank of pollen tubes. We demonstrate that the physiological features of polarised growth in the pollen tube can be explained by the localised distribution of transporters at the tip and shank. Model analysis reveals that the tip and shank compartments integrate into a self-regulatory dynamic system, however the oscillatory dynamics at the tip do not play an important role in maintaining ion gradients. Furthermore, an electric current travelling along the pollen tube contributes to the regulation of ion dynamics. Two candidate mechanisms for growth-induced oscillations are proposed: the transition of tip membrane into shank membrane, and growth-induced changes in kinetic parameters of ion transporters. The methodology and principles developed here are applicable to the study of ion dynamics and their interactions with other functional modules in any plant cellular system.
Collapse
Affiliation(s)
- Junli Liu
- School of Biological and Biomedical Sciences, University of Durham, Durham, United Kingdom
- Biophysical Sciences Institute, University of Durham, Durham, United Kingdom
| | - Bernard M. A. G. Piette
- Department of Mathematical Sciences, University of Durham, Durham, United Kingdom
- Biophysical Sciences Institute, University of Durham, Durham, United Kingdom
| | - Michael J. Deeks
- School of Biological and Biomedical Sciences, University of Durham, Durham, United Kingdom
- Biophysical Sciences Institute, University of Durham, Durham, United Kingdom
| | | | - Patrick J. Hussey
- School of Biological and Biomedical Sciences, University of Durham, Durham, United Kingdom
- Biophysical Sciences Institute, University of Durham, Durham, United Kingdom
| |
Collapse
|
18
|
|
19
|
Abstract
Spatial-temporal flexibility of the actin filament network (F-actin) is essential for all basic cellular functions and is governed by a stochastic dynamic model. In this model, actin filaments that randomly polymerise from a pool of free actin are bundled with other filaments and severed by ADF/cofilin. The fate of the severed fragments is not known. It has been proposed that the fragments are disassembled and the monomeric actin recycled for the polymerisation of new filaments. Here, we have generated tobacco cell lines and Arabidopsis plants expressing the actin marker Lifeact to address the mechanisms of F-actin reorganisation in vivo. We found that F-actin is more dynamic in isotropically expanding cells and that the density of the network changes with a periodicity of 70 seconds. The depolymerisation rate, but not the polymerisation rate, of F-actin increases when microtubules are destabilised. New filaments can be assembled from shorter free cytoplasmic fragments, from the products of F-actin severing and by polymerisation from the ends of extant filaments. Thus, remodelling of F-actin might not require bulk depolymerisation of the entire network, but could occur via severing and end-joining of existing polymers.
Collapse
Affiliation(s)
- Andrei P. Smertenko
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| | - Michael J. Deeks
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| | - Patrick J. Hussey
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| |
Collapse
|
20
|
Deeks MJ, Fendrych M, Smertenko A, Bell KS, Oparka K, Cvrčková F, Žárský V, Hussey PJ. The plant formin AtFH4 interacts with both actin and microtubules, and contains a newly identified microtubule-binding domain. J Cell Sci 2010; 123:1209-15. [PMID: 20332108 DOI: 10.1242/jcs.065557] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The dynamic behaviour of the actin cytoskeleton in plants relies on the coordinated action of several classes of actin-binding proteins (ABPs). These ABPs include the plant-specific subfamilies of actin-nucleating formin proteins. The model plant species Arabidopsis thaliana has over 20 formin proteins, all of which contain plant-specific regions in place of the GTPase-binding domain, formin homology (FH)3 domain, and DAD and DID motifs found in many fungal and animal formins. We have identified for the first time a plant-specific region of the membrane-integrated formin AtFH4 that mediates an association with the microtubule cytoskeleton. In vitro analysis shows that this region (named the GOE domain) binds directly to microtubules. Overexpressed AtFH4 accumulates at the endoplasmic reticulum membrane and co-aligns the endoplasmic reticulum with microtubules. The FH1 and FH2 domains of formins are conserved in plants, and we show that these domains of AtFH4 nucleate F-actin. Together, these data suggest that the combination of plant-specific and conserved domains enables AtFH4 to function as an interface between membranes and both major cytoskeletal networks.
Collapse
Affiliation(s)
- Michael J. Deeks
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| | - Matyáš Fendrych
- Department of Plant Physiology, Faculty of Sciences, Charles University, Prague 12844, Czech Republic
- Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Prague 16502, Czech Republic
| | - Andrei Smertenko
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| | - Kenneth S. Bell
- Institute of Molecular Plant Sciences, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, UK
| | - Karl Oparka
- Institute of Molecular Plant Sciences, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, UK
| | - Fatima Cvrčková
- Department of Plant Physiology, Faculty of Sciences, Charles University, Prague 12844, Czech Republic
| | - Viktor Žárský
- Department of Plant Physiology, Faculty of Sciences, Charles University, Prague 12844, Czech Republic
- Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Prague 16502, Czech Republic
| | - Patrick J. Hussey
- School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| |
Collapse
|
21
|
Deeks MJ, Rodrigues C, Dimmock S, Ketelaar T, Maciver SK, Malhó R, Hussey PJ. Arabidopsis CAP1 – a key regulator of actin organisation and development. J Cell Sci 2007; 120:2609-18. [PMID: 17635992 DOI: 10.1242/jcs.007302] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Maintenance of F-actin turnover is essential for plant cell morphogenesis. Actin-binding protein mutants reveal that plants place emphasis on particular aspects of actin biochemistry distinct from animals and fungi. Here we show that mutants in CAP1, an A. thaliana member of the cyclase-associated protein family, display a phenotype that establishes CAP1 as a fundamental facilitator of actin dynamics over a wide range of plant tissues. Plants homozygous for cap1 alleles show a reduction in stature and morphogenetic disruption of multiple cell types. Pollen grains exhibit reduced germination efficiency, and cap1 pollen tubes and root hairs grow at a decreased rate and to a reduced length. Live cell imaging of growing root hairs reveals actin filament disruption and cytoplasmic disorganisation in the tip growth zone. Mutant cap1 alleles also show synthetic phenotypes when combined with mutants of the Arp2/3 complex pathway, which further suggests a contribution of CAP1 to in planta actin dynamics. In yeast, CAP interacts with adenylate cyclase in a Ras signalling cascade; but plants do not have Ras. Surprisingly, cap1 plants show disruption in plant signalling pathways required for co-ordinated organ expansion suggesting that plant CAP has evolved to attain plant-specific signalling functions.
Collapse
Affiliation(s)
- Michael J Deeks
- The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, Durham University, South Road, Durham, DH1 3LE, UK
| | | | | | | | | | | | | |
Collapse
|
22
|
Uhrig JF, Mutondo M, Zimmermann I, Deeks MJ, Machesky LM, Thomas P, Uhrig S, Rambke C, Hussey PJ, Hülskamp M. The role of Arabidopsis SCAR genes in ARP2-ARP3-dependent cell morphogenesis. Development 2007; 134:967-77. [PMID: 17267444 DOI: 10.1242/dev.02792] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The actin-nucleating ARP2-ARP3 complex controls cell shape in plants in many different cell types. Its activity is controlled by a multimeric complex containing BRK1 (also known as HSPC300), NAP1, SRA1, ABI and SCAR/WAVE. In this study, we focus on the function of the five putative SCAR homologues in Arabidopsis and we provide biochemical evidence that AtSCAR2 can activate the ARP2-ARP3 complex in vitro. Among the single mutants, mutations in only AtSCAR2 result in a subtle or weak phenotype similar to ARP2, ARP3 and other `distorted' mutants. Double-mutant analysis revealed a redundancy with AtSCAR4. Systematic application of the yeast two-hybrid system and Bimolecular Fluorescence Complementation (BiFC)revealed a complex protein-interaction network between the ARP2-ARP3 complex and its genetically defined regulators. In addition to protein interactions known in other systems, we identified several new interactions, suggesting that SPIKE1 may be an integral component of the SCAR/WAVE complex and that SCAR proteins in plants might act as direct effectors of ROP GTPases.
Collapse
Affiliation(s)
- Joachim F Uhrig
- University of Köln, Botanical Institute III, Gyrhofstr. 15, 50931 Köln, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Abstract
Plant cells grow through increases in volume and cell wall surface area. The mature morphology of a plant cell is a product of the differential rates of expansion between neighboring zones of the cell wall during this process. Filamentous actin arrays are associated with plant cell growth, and the activity of actin-binding proteins is proving to be essential for proper cell morphogenesis. Actin-nucleating proteins participate in cell expansion and cell plate formation whereas the recycling of actin monomers is required to maintain actin dynamics and controlled growth. Coordination of actin-binding protein activity and other aspects of cytoskeletal behavior during cell development maintains cohesive cell expansion. Emerging plant signaling networks are proving to be powerful regulators of morphology-shaping cytoskeletal activity, and in this review we highlight current research in actin network regulation.
Collapse
Affiliation(s)
- Patrick J Hussey
- 1The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, Science Laboratories, Durham DH1 3LE, United Kingdom.
| | | | | |
Collapse
|
24
|
Deeks MJ, Cvrcková F, Machesky LM, Mikitová V, Ketelaar T, Zársky V, Davies B, Hussey PJ. Arabidopsis group Ie formins localize to specific cell membrane domains, interact with actin-binding proteins and cause defects in cell expansion upon aberrant expression. New Phytol 2005; 168:529-40. [PMID: 16313636 DOI: 10.1111/j.1469-8137.2005.01582.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The closely related proteins AtFH4 and AtFH8 represent the group Ie clade of Arabidopsis formin homologues. The subcellular localization of these proteins and their ability to affect the actin cytoskeleton were examined. AtFH4 protein activity was identified using fluorimetric techniques. Interactions between Arabidopsis profilin isoforms and AtFH4 were assayed in vitro and in vivo using pull-down assays and yeast-2-hybrid. The subcellular localization of group Ie formins was observed with indirect immunofluorescence (AtFH4) and an ethanol-inducible green fluorescent protein (GFP) fusion construct (AtFH8). AtFH4 protein affected actin dynamics in vitro, and yeast-2-hybrid assays suggested isoform-specific interactions with the actin-binding protein profilin in vivo. Indirect immunofluorescence showed that AtFH4 localized specifically to the cell membrane at borders between adjoining cells. Expression of an AtFH8 fusion protein resulted in GFP localization to cell membrane zones, similar to AtFH4. Furthermore, aberrant expression of AtFH8 resulted in the inhibition of root hair elongation. Taken together, these data suggest that the group Ie formins act with profilin to regulate actin polymerization at specific sites associated with the cell membrane.
Collapse
Affiliation(s)
- Michael J Deeks
- The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, Science Laboratories, South Road, Durham DH1 3LE, UK
| | | | | | | | | | | | | | | |
Collapse
|
25
|
Abstract
The actin-nucleating Arp2/3 complex is essential for life in yeast and animals, but not in plants, in which mutants of Arp2/3 complex components show relatively minor developmental abnormalities. Animal cells control the activity of the Arp2/3 complex through the suppressor of cyclic AMP receptor (SCAR) complex to achieve cell motility. Amazingly, plants have also retained the SCAR cell-motility pathway, and now provide a unique model for the study of new aspects of SCAR function in the absence of cell motility.
Collapse
Affiliation(s)
- Michael J Deeks
- The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, South Road, Durham, DH1 3LE, UK
| | | |
Collapse
|
26
|
Deeks MJ, Kaloriti D, Davies B, Malhó R, Hussey PJ. Arabidopsis NAP1 Is Essential for Arp2/3-Dependent Trichome Morphogenesis. Curr Biol 2004; 14:1410-4. [PMID: 15296761 DOI: 10.1016/j.cub.2004.06.065] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2004] [Revised: 06/18/2004] [Accepted: 06/21/2004] [Indexed: 11/23/2022]
Abstract
The dynamic nature of the eukaryotic actin cytoskeleton is essential for the locomotion of animal cells and the morphogenesis of plant and fungal cells. The F-actin nucleating/branching activity of the Arp2/3 complex is a key function for all of these processes. The SCAR/WAVE family represents a group of Arp2/3 activators that are associated with lamellipodia formation. A protein complex of PIR121, NAP1, ABI, and HSPC300 is required for SCAR regulation by cell signaling pathways, but the exact nature of this interaction is controversial and represents a continually evolving model. The mechanism originally proposed was of a SCAR trans repressing complex supported by evidence from in vitro experiments. This model was reinforced by genetic studies in the Drosophila central nervous system and Dictyostelium, where the knockout of certain SCAR-complex components leads to excessive SCAR-mediated actin polymerization. Conflicting data have steadily accumulated from animal tissue culture experiments suggesting that the complex activates rather than represses in vivo SCAR activity. Recent biochemical evidence supports the SCAR-complex activator model. Here, we show that genetic observations in Arabidopsis are compatible with an activation model and provide one potential mechanism for the regulation of the newly identified Arabidopsis Arp2/3 complex.
Collapse
Affiliation(s)
- Michael J Deeks
- The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, United Kingdom
| | | | | | | | | |
Collapse
|
27
|
Abstract
The shape of plant cells is reliant upon an organised actin network. A series of recent publications have emphasised the central role played by the actin-nucleating Arp2/3 complex in plant growth. In animals and fungi, the Arp2/3 complex influences cell motility and morphogenesis through its ability to nucleate actin filaments locally in response to cell signalling pathways. There are potential parallels in the action and control of the Arp2/3 complex in plants and animals.
Collapse
Affiliation(s)
- Michael J Deeks
- The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, South Road, Durham DH1 3LE, UK
| | | |
Collapse
|
28
|
Abstract
The control of cell growth and polarity depends on a dynamic actin cytoskeleton that has the ability to reorganize in response to developmental and environmental stimuli. In animals and fungi, formins are just one of the four major classes of poly-L-proline-containing (PLP) proteins that form part of the signal-transduction cascade that leads to rearrangement of the actin cytoskeleton. Analysis of the Arabidopsis genome sequence indicates that, unlike animals and fungi, formins are the only class of conserved profilin-binding PLP proteins in plants. Moreover, plant formins show significant structural differences compared with their animal and fungal counterparts, raising the possibility that plant formins are subject to novel mechanisms of control or perform unique roles in plants.
Collapse
Affiliation(s)
- Michael J Deeks
- The Integrative Cell Biology Laboratory, School of Biological and Biomedical Sciences, University of Durham, South Road, UK DH1 3LE.
| | | | | |
Collapse
|