1
|
Yuan G, Gao H, Yang T. Exploring the Role of the Plant Actin Cytoskeleton: From Signaling to Cellular Functions. Int J Mol Sci 2023; 24:15480. [PMID: 37895158 PMCID: PMC10607326 DOI: 10.3390/ijms242015480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 10/06/2023] [Accepted: 10/21/2023] [Indexed: 10/29/2023] Open
Abstract
The plant actin cytoskeleton is characterized by the basic properties of dynamic array, which plays a central role in numerous conserved processes that are required for diverse cellular functions. Here, we focus on how actins and actin-related proteins (ARPs), which represent two classical branches of a greatly diverse superfamily of ATPases, are involved in fundamental functions underlying signal regulation of plant growth and development. Moreover, we review the structure, assembly dynamics, and biological functions of filamentous actin (F-actin) from a molecular perspective. The various accessory proteins known as actin-binding proteins (ABPs) partner with F-actin to finely tune actin dynamics, often in response to various cell signaling pathways. Our understanding of the significance of the actin cytoskeleton in vital cellular activities has been furthered by comparison of conserved functions of actin filaments across different species combined with advanced microscopic techniques and experimental methods. We discuss the current model of the plant actin cytoskeleton, followed by examples of the signaling mechanisms under the supervision of F-actin related to cell morphogenesis, polar growth, and cytoplasmic streaming. Determination of the theoretical basis of how the cytoskeleton works is important in itself and is beneficial to future applications aimed at improving crop biomass and production efficiency.
Collapse
Affiliation(s)
| | | | - Tao Yang
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou 730000, China; (G.Y.); (H.G.)
| |
Collapse
|
2
|
Ishida H, Woodman AG, Kitada N, Aizawa T, Vogel HJ. The Dictyostelium discoideum FimA protein, unlike yeast and plant fimbrins, is regulated by calcium similar to mammalian plastins. Sci Rep 2023; 13:16208. [PMID: 37758724 PMCID: PMC10533516 DOI: 10.1038/s41598-023-42682-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 09/13/2023] [Indexed: 09/29/2023] Open
Abstract
Plastins, also known as fimbrins, are highly conserved eukaryotic multidomain proteins that are involved in actin-bundling. They all contain four independently folded Calponin Homology-domains and an N-terminal headpiece that is comprised of two calcium-binding EF-hand motifs. Since calcium-binding has been shown to be integral to regulating the activity of the three mammalian plastin proteins, we decided to study the properties of the headpiece regions of fimbrins from the model plant Arabidopsis thaliana, the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe and the amoeba Dictyostelium discoideum. Of these protein domains only the FimA headpiece from the amoeba protein possesses calcium binding properties. Structural characterization of this protein domain by multidimensional NMR and site-directed mutagenesis studies indicates that this EF-hand region of FimA also contains a regulatory 'switch helix' that is essential to regulating the activity of the human L-plastin protein. Interestingly this regulatory helical region seems to be lacking in the plant and yeast proteins and in fimbrins from all other nonmotile systems. Typical calmodulin antagonists can displace the switch-helix from the FimA headpiece, suggesting that such drugs can deregulate the Ca2+-regulation of the actin-bunding in the amoeba, thereby making it a useful organism for drug screening against mammalian plastins.
Collapse
Affiliation(s)
- Hiroaki Ishida
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | - Andrew G Woodman
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, AB, T2N 1N4, Canada
| | - Naoya Kitada
- Faculty of Advanced Life Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Tomoyasu Aizawa
- Faculty of Advanced Life Science, Hokkaido University, Sapporo, 060-0810, Japan
| | - Hans J Vogel
- Biochemistry Research Group, Department of Biological Sciences, University of Calgary, Calgary, AB, T2N 1N4, Canada.
| |
Collapse
|
3
|
Wang Q, Xu Y, Zhao S, Jiang Y, Yi R, Guo Y, Huang S. Activation of actin-depolymerizing factor by CDPK16-mediated phosphorylation promotes actin turnover in Arabidopsis pollen tubes. PLoS Biol 2023; 21:e3002073. [PMID: 37011088 PMCID: PMC10101649 DOI: 10.1371/journal.pbio.3002073] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 04/13/2023] [Accepted: 03/11/2023] [Indexed: 04/05/2023] Open
Abstract
As the stimulus-responsive mediator of actin dynamics, actin-depolymerizing factor (ADF)/cofilin is subject to tight regulation. It is well known that kinase-mediated phosphorylation inactivates ADF/cofilin. Here, however, we found that the activity of Arabidopsis ADF7 is enhanced by CDPK16-mediated phosphorylation. We found that CDPK16 interacts with ADF7 both in vitro and in vivo, and it enhances ADF7-mediated actin depolymerization and severing in vitro in a calcium-dependent manner. Accordingly, the rate of actin turnover is reduced in cdpk16 pollen and the amount of actin filaments increases significantly at the tip of cdpk16 pollen tubes. CDPK16 phosphorylates ADF7 at Serine128 both in vitro and in vivo, and the phospho-mimetic mutant ADF7S128D has enhanced actin-depolymerizing activity compared to ADF7. Strikingly, we found that failure in the phosphorylation of ADF7 at Ser128 impairs its function in promoting actin turnover in vivo, which suggests that this phospho-regulation mechanism is biologically significant. Thus, we reveal that CDPK16-mediated phosphorylation up-regulates ADF7 to promote actin turnover in pollen.
Collapse
Affiliation(s)
- Qiannan Wang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yanan Xu
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Shuangshuang Zhao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, China
- Key Laboratory of Plant Stress, Life Science College, Shandong Normal University, Jinan, China
| | - Yuxiang Jiang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Ran Yi
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Yan Guo
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, China
| | - Shanjin Huang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, China
| |
Collapse
|
4
|
Rajan S, Kudryashov DS, Reisler E. Actin Bundles Dynamics and Architecture. Biomolecules 2023; 13:450. [PMID: 36979385 PMCID: PMC10046292 DOI: 10.3390/biom13030450] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2022] [Revised: 02/16/2023] [Accepted: 02/20/2023] [Indexed: 03/04/2023] Open
Abstract
Cells use the actin cytoskeleton for many of their functions, including their division, adhesion, mechanosensing, endo- and phagocytosis, migration, and invasion. Actin bundles are the main constituent of actin-rich structures involved in these processes. An ever-increasing number of proteins that crosslink actin into bundles or regulate their morphology is being identified in cells. With recent advances in high-resolution microscopy and imaging techniques, the complex process of bundles formation and the multiple forms of physiological bundles are beginning to be better understood. Here, we review the physiochemical and biological properties of four families of highly conserved and abundant actin-bundling proteins, namely, α-actinin, fimbrin/plastin, fascin, and espin. We describe the similarities and differences between these proteins, their role in the formation of physiological actin bundles, and their properties-both related and unrelated to their bundling abilities. We also review some aspects of the general mechanism of actin bundles formation, which are known from the available information on the activity of the key actin partners involved in this process.
Collapse
Affiliation(s)
- Sudeepa Rajan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
| | - Dmitri S. Kudryashov
- Department of Chemistry and Biochemistry, Ohio State University, Columbus, OH 43210, USA
| | - Emil Reisler
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095, USA
- Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA
| |
Collapse
|
5
|
Zhang Y, An B, Wang W, Zhang B, He C, Luo H, Wang Q. Actin-bundling protein fimbrin regulates pathogenicity via organizing F-actin dynamics during appressorium development in Colletotrichum gloeosporioides. MOLECULAR PLANT PATHOLOGY 2022; 23:1472-1486. [PMID: 35791045 PMCID: PMC9452767 DOI: 10.1111/mpp.13242] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 06/12/2022] [Accepted: 06/14/2022] [Indexed: 06/15/2023]
Abstract
Anthracnose caused by Colletotrichum gloeosporioides leads to serious economic loss to rubber tree yield and other tropical crops. The appressorium, a specialized dome-shaped infection structure, plays a crucial role in the pathogenesis of C. gloeosporioides. However, the mechanism of how actin cytoskeleton dynamics regulate appressorium formation and penetration remains poorly defined in C. gloeosporioides. In this study, an actin cross-linking protein fimbrin homologue (CgFim1) was identified in C. gloeosporioides, and the knockout of CgFim1 led to impairment in vegetative growth, conidiation, and pathogenicity. We then investigated the roles of CgFim1 in the dynamic organization of the actin cytoskeleton. We observed that actin patches and cables localized at the apical and subapical regions of the hyphal tip, and showed a disc-to-ring dynamic around the pore during appressorium development. CgFim1 showed a similar distribution pattern to the actin cytoskeleton. Moreover, knockout of CgFim1 affected the polarity of the actin cytoskeleton in the hyphal tip and disrupted the actin dynamics and ring structure formation in the appressorium, which prevented polar growth and appressorium development. The CgFim1 mutant also interfered with the septin structure formation. This caused defects in pore wall overlay formation, pore contraction, and the extension of the penetration peg. These results reveal the mechanism by which CgFim1 regulates the growth and pathogenicity of C. gloeosporioides by organizing the actin cytoskeleton.
Collapse
Affiliation(s)
- Yi Zhang
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresource, Key Laboratory of Biotechnology of Salt Tolerant Crops of Hainan ProvinceCollege of Tropical Crops, Hainan UniversityHaikouChina
- Sanya Nanfan Research Institute of Hainan University, Hainan Yazhou Bay Seed LaboratorySanyaChina
| | - Bang An
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresource, Key Laboratory of Biotechnology of Salt Tolerant Crops of Hainan ProvinceCollege of Tropical Crops, Hainan UniversityHaikouChina
- Sanya Nanfan Research Institute of Hainan University, Hainan Yazhou Bay Seed LaboratorySanyaChina
| | - Wenfeng Wang
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresource, Key Laboratory of Biotechnology of Salt Tolerant Crops of Hainan ProvinceCollege of Tropical Crops, Hainan UniversityHaikouChina
| | - Bei Zhang
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresource, Key Laboratory of Biotechnology of Salt Tolerant Crops of Hainan ProvinceCollege of Tropical Crops, Hainan UniversityHaikouChina
- Sanya Nanfan Research Institute of Hainan University, Hainan Yazhou Bay Seed LaboratorySanyaChina
| | - Chaozu He
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresource, Key Laboratory of Biotechnology of Salt Tolerant Crops of Hainan ProvinceCollege of Tropical Crops, Hainan UniversityHaikouChina
- Sanya Nanfan Research Institute of Hainan University, Hainan Yazhou Bay Seed LaboratorySanyaChina
| | - Hongli Luo
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresource, Key Laboratory of Biotechnology of Salt Tolerant Crops of Hainan ProvinceCollege of Tropical Crops, Hainan UniversityHaikouChina
- Sanya Nanfan Research Institute of Hainan University, Hainan Yazhou Bay Seed LaboratorySanyaChina
| | - Qiannan Wang
- Hainan Key Laboratory for Sustainable Utilization of Tropical Bioresource, Key Laboratory of Biotechnology of Salt Tolerant Crops of Hainan ProvinceCollege of Tropical Crops, Hainan UniversityHaikouChina
- Sanya Nanfan Research Institute of Hainan University, Hainan Yazhou Bay Seed LaboratorySanyaChina
| |
Collapse
|
6
|
Pain C, Tolmie F, Wojcik S, Wang P, Kriechbaumer V. intER-ACTINg: the structure and dynamics of ER and actin are interlinked. J Microsc 2022. [PMID: 35985796 DOI: 10.1111/jmi.13139] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 08/09/2022] [Accepted: 08/10/2022] [Indexed: 11/30/2022]
Abstract
The actin cytoskeleton is the driver of gross ER remodelling and the movement and positioning of other membrane-bound organelles such as Golgi bodies. Rapid ER membrane remodelling is a feature of most plant cells and is important for normal cellular processes, including targeted secretion, immunity and signalling. Modifications to the actin cytoskeleton, through pharmacological agents such as Latrunculin B and phalloidin, or disruption of normal myosin function also affect ER structure and/or dynamics. Here, we investigate the impact of changes in the actin cytoskeleton on structure and dynamics on the ER as well as in return the impact of modified ER structure on the architecture of the actin cytoskeleton. By expressing actin markers that affect actin dynamics, or expressing of ER-shaping proteins that influence ER architecture, we found that the structure of ER-actin networks is closely inter-related; affecting one component is likely to have a direct effect on the other. Therefore, our results indicate that a complicated regulatory machinery and cross-talk between these two structures must exist in plants to co-ordinate the function of ER-actin network during multiple subcellular processes. In addition, when considering organelle structure and dynamics, the choice of actin marker is essential in preventing off-target organelle structure and dynamics modifications. This article is protected by copyright. All rights reserved.
Collapse
Affiliation(s)
- Charlotte Pain
- Plant Cell Biology, Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Frances Tolmie
- Plant Cell Biology, Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Stefan Wojcik
- Plant Cell Biology, Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Pengwei Wang
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), College of Horticulture and Forestry Science, Huazhong Agricultural University, Wuhan, 430070, China
| | - Verena Kriechbaumer
- Plant Cell Biology, Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK
| |
Collapse
|
7
|
Allosteric regulation controls actin-bundling properties of human plastins. Nat Struct Mol Biol 2022; 29:519-528. [PMID: 35589838 DOI: 10.1038/s41594-022-00771-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 04/05/2022] [Indexed: 11/08/2022]
Abstract
Plastins/fimbrins are conserved actin-bundling proteins contributing to motility, cytokinesis and other cellular processes by organizing strikingly different actin assemblies as in aligned bundles and branched networks. We propose that this ability of human plastins stems from an allosteric communication between their actin-binding domains (ABD1/2) engaged in a tight spatial association. Here we show that ABD2 can bind actin three orders of magnitude stronger than ABD1, unless the domains are involved in an equally strong inhibitory engagement. A mutation mimicking physiologically relevant phosphorylation at the ABD1-ABD2 interface greatly weakened their association, dramatically potentiating actin cross-linking. Cryo-EM reconstruction revealed the ABD1-actin interface and enabled modeling of the plastin bridge and domain separation in parallel bundles. We predict that a strong and tunable allosteric inhibition between the domains allows plastins to modulate the cross-linking strength, contributing to remodeling of actin assemblies of different morphologies defining the unique place of plastins in actin organization.
Collapse
|
8
|
Schaffner-Reckinger E, Machado RAC. The actin-bundling protein L-plastin-A double-edged sword: Beneficial for the immune response, maleficent in cancer. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2020; 355:109-154. [PMID: 32859369 DOI: 10.1016/bs.ircmb.2020.05.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The dynamic organization of the actin cytoskeleton into bundles and networks is orchestrated by a large variety of actin-binding proteins. Among them, the actin-bundling protein L-plastin is normally expressed in hematopoietic cells, where it is involved in the immune response. However, L-plastin is also often ectopically expressed in malignant cancer cells of non-hematopoietic origin and is even considered as a marker for cancer progression. Post-translational modification modulates L-plastin activity. In particular, L-plastin Ser5 phosphorylation has been shown to be important for the immune response in leukocytes as well as for invasion and metastasis formation of carcinoma cells. This chapter discusses the physiological and pathological role of L-plastin with a special focus on the importance of L-plastin Ser5 phosphorylation for the protein functions. The potential use of Ser5 phosphorylated L-plastin as a biomarker and/or therapeutic target will be evoked.
Collapse
Affiliation(s)
- Elisabeth Schaffner-Reckinger
- Cancer Cell Biology and Drug Discovery Group, Faculty of Science, Technology and Medicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg.
| | - Raquel A C Machado
- Cancer Cell Biology and Drug Discovery Group, Faculty of Science, Technology and Medicine, University of Luxembourg, Esch-sur-Alzette, Luxembourg
| |
Collapse
|
9
|
Ergin V, Zheng S. Putative Coiled-Coil Domain-Dependent Autoinhibition and Alternative Splicing Determine SHTN1's Actin-Binding Activity. J Mol Biol 2020; 432:4154-4166. [PMID: 32371045 DOI: 10.1016/j.jmb.2020.04.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Revised: 04/23/2020] [Accepted: 04/28/2020] [Indexed: 11/16/2022]
Abstract
The actin cytoskeleton plays a pivotal role in cell development, morphogenesis, and other cellular functions. Precise control of actin dynamics requires actin-binding proteins. Here, we characterize multifarious regulation of SHTN1 (shootin1) and show that, unlike known actin-binding proteins, SHTN1's actin binding activity is intrinsically inhibited by a putative coiled-coil domain (CCD) and the autoinhibition is overcome by alternative splicing regulation. We found SHTN1 contains a noncanonical WH2 domain and an upstream proline-rich region (PRR) that by themselves are sufficient for actin interaction. Alternative splicing of Shtn1 at the C terminus and downstream of the WH2-PRR domain produces a long (SHTN1L or shootin1b) and a short (SHTN1S or shootin1a) isoform, which both contain the described PRR and WH2 domains. However, SHTN1S does not interact with actin due to inhibition mediated by an N-terminal CCD. A SHTN1L-specific C-terminal motif counters the intramolecular inhibition and allows SHNT1L to bind actin. A nuclear localization signal is embedded between PRR and WH2 and is subject to similar autoinhibition. SHTN1 would be the first WH2-containing molecule that adopts CCD-dependent autoinhibition and alternative splicing-dependent actin interaction.
Collapse
Affiliation(s)
- Volkan Ergin
- Division of Biomedical Sciences, University of California, Riverside, Riverside, CA 92521, USA
| | - Sika Zheng
- Division of Biomedical Sciences, University of California, Riverside, Riverside, CA 92521, USA.
| |
Collapse
|
10
|
Zhao W, Qu X, Zhuang Y, Wang L, Bosch M, Franklin-Tong VE, Xue Y, Huang S. Villin controls the formation and enlargement of punctate actin foci in pollen tubes. J Cell Sci 2020; 133:jcs237404. [PMID: 32051284 DOI: 10.1242/jcs.237404] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 02/01/2020] [Indexed: 11/20/2022] Open
Abstract
Self-incompatibility (SI) in the poppy Papaver rhoeas triggers dramatic alterations in actin within pollen tubes. However, how these actin alterations are mechanistically achieved remains largely unexplored. Here, we used treatment with the Ca2+ ionophore A23187 to mimic the SI-induced elevation in cytosolic Ca2+ and trigger formation of the distinctive F-actin foci. Live-cell imaging revealed that this remodeling involves F-actin fragmentation and depolymerization, accompanied by the rapid formation of punctate actin foci and subsequent increase in their size. We established that actin foci are generated and enlarged from crosslinking of fragmented actin filament structures. Moreover, we show that villins associate with actin structures and are involved in this actin reorganization process. Notably, we demonstrate that Arabidopsis VILLIN5 promotes actin depolymerization and formation of actin foci by fragmenting actin filaments, and controlling the enlargement of actin foci via bundling of actin filaments. Our study thus uncovers important novel insights about the molecular players and mechanisms involved in forming the distinctive actin foci in pollen tubes.
Collapse
Affiliation(s)
- Wanying Zhao
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Xiaolu Qu
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
- Key Laboratory of Horticultural Plant Biology (Ministry of Education), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China
| | - Yuhui Zhuang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Ludi Wang
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Plas Gogerddan, Aberystwyth, SY23 3EE, UK
| | - Maurice Bosch
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Plas Gogerddan, Aberystwyth, SY23 3EE, UK
| | - Vernonica E Franklin-Tong
- School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Yongbiao Xue
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China
- Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, 100101, China
| | - Shanjin Huang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| |
Collapse
|
11
|
Li YB, Xu R, Liu C, Shen N, Han LB, Tang D. Magnaporthe oryzae fimbrin organizes actin networks in the hyphal tip during polar growth and pathogenesis. PLoS Pathog 2020; 16:e1008437. [PMID: 32176741 PMCID: PMC7098657 DOI: 10.1371/journal.ppat.1008437] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 03/26/2020] [Accepted: 02/26/2020] [Indexed: 01/19/2023] Open
Abstract
Magnaporthe oryzae causes rice blast disease, but little is known about the dynamic restructuring of the actin cytoskeleton during its polarized tip growth and pathogenesis. Here, we used super-resolution live-cell imaging to investigate the dynamic organization of the actin cytoskeleton in M. oryzae during hyphal tip growth and pathogenesis. We observed a dense actin network at the apical region of the hyphae and actin filaments originating from the Spitzenkörper (Spk, the organizing center for hyphal growth and development) that formed branched actin bundles radiating to the cell membrane. The actin cross-linking protein Fimbrin (MoFim1) helps organize this actin distribution. MoFim1 localizes to the actin at the subapical collar, the actin bundles, and actin at the Spk. Knockout of MoFim1 resulted in impaired Spk maintenance and reduced actin bundle formation, preventing polar growth, vesicle transport, and the expansion of hyphae in plant cells. Finally, transgenic rice (Oryza sativa) expressing RNA hairpins targeting MoFim1 exhibited improved resistance to M. oryzae infection, indicating that MoFim1 represents an excellent candidate for M. oryzae control. These results reveal the dynamics of actin assembly in M. oryzae during hyphal tip development and pathogenesis, and they suggest a mechanism in which MoFim1 organizes such actin networks.
Collapse
Affiliation(s)
- Yuan-Bao Li
- State Key Laboratory of Ecological Control of Fujian-Taiwan Crop Pests, Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, Plant Immunity Center, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
- College of Agriculture, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - Rui Xu
- State Key Laboratory of Ecological Control of Fujian-Taiwan Crop Pests, Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, Plant Immunity Center, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
- College of Agriculture, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - Chengyu Liu
- State Key Laboratory of Ecological Control of Fujian-Taiwan Crop Pests, Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, Plant Immunity Center, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
- College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - Ningning Shen
- State Key Laboratory of Ecological Control of Fujian-Taiwan Crop Pests, Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, Plant Immunity Center, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
- College of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - Li-Bo Han
- State Key Laboratory of Ecological Control of Fujian-Taiwan Crop Pests, Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, Plant Immunity Center, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - Dingzhong Tang
- State Key Laboratory of Ecological Control of Fujian-Taiwan Crop Pests, Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, Plant Immunity Center, Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| |
Collapse
|
12
|
Madina MH, Rahman MS, Zheng H, Germain H. Vacuolar membrane structures and their roles in plant-pathogen interactions. PLANT MOLECULAR BIOLOGY 2019; 101:343-354. [PMID: 31621005 DOI: 10.1007/s11103-019-00921-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 10/04/2019] [Indexed: 06/10/2023]
Abstract
Short review focussing on the role and targeting of vacuolar substructure in plant immunity and pathogenesis. Plants lack specialized immune cells, therefore each plant cell must defend itself against invading pathogens. A typical plant defense strategy is the hypersensitive response that results in host cell death at the site of infection, a process largely regulated by the vacuole. In plant cells, the vacuole is a vital organelle that plays a central role in numerous fundamental processes, such as development, reproduction, and cellular responses to biotic and abiotic stimuli. It shows divergent membranous structures that are continuously transforming. Recent technical advances in visualization and live-cell imaging have significantly altered our view of the vacuolar structures and their dynamics. Understanding the active nature of the vacuolar structures and the mechanisms of vacuole-mediated defense responses is of great importance in understanding plant-pathogen interactions. In this review, we present an overview of the current knowledge about the vacuole and its internal structures, as well as their role in plant-microbe interactions. There is so far limited information on the modulation of the vacuolar structures by pathogens, but recent research has identified the vacuole as a possible target of microbial interference.
Collapse
Affiliation(s)
- Mst Hur Madina
- Department of Chemistry, Biochemistry and Physics, Université du Québec à Trois-Rivières, 3351 boulevard des Forges, Trois-Rivières, QC, G9A 5H7, Canada
| | - Md Saifur Rahman
- Department of Chemistry, Biochemistry and Physics, Université du Québec à Trois-Rivières, 3351 boulevard des Forges, Trois-Rivières, QC, G9A 5H7, Canada
| | - Huanquan Zheng
- Department of Biology, McGill University, 1205 Dr. Penfield Avenue, Montreal, QC, H3A 1B1, Canada
| | - Hugo Germain
- Department of Chemistry, Biochemistry and Physics, Université du Québec à Trois-Rivières, 3351 boulevard des Forges, Trois-Rivières, QC, G9A 5H7, Canada.
| |
Collapse
|
13
|
AP3M harbors actin filament binding activity that is crucial for vacuole morphology and stomatal closure in Arabidopsis. Proc Natl Acad Sci U S A 2019; 116:18132-18141. [PMID: 31431522 DOI: 10.1073/pnas.1901431116] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Stomatal movement is essential for plant growth. This process is precisely regulated by various cellular activities in guard cells. F-actin dynamics and vacuole morphology are both involved in stomatal movement. The sorting of cargoes by clathrin adaptor protein (AP) complexes from the Golgi to the vacuole is critical for establishing a normal vacuole morphology. In this study, we demonstrate that the medium subunit of the AP3 complex (AP3M) binds to and severs actin filaments in vitro and that it participates in the sorting of cargoes (such as the sucrose exporter SUC4) to the tonoplast, and thereby regulates stomatal closure in Arabidopsis thaliana Defects in AP3 or SUC4 led to more rapid water loss and delayed stomatal closure, as well as hypersensitivity to drought stress. In ap3m mutants, the F-actin status was altered compared to the wild type, and the sorted cargoes failed to localize to the tonoplast. AP3M contains a previously unidentified F-actin binding domain that is conserved in AP3M homologs in both plants and animals. Mutations in the F-actin binding domain of AP3M abolished its F-actin binding activity in vitro, leading to an aberrant vacuole morphology and reduced levels of SUC4 on the tonoplast in guard cells. Our findings indicate that the F-actin binding activity of AP3M is required for the precise localization of AP3-dependent cargoes to the tonoplast and for the regulation of vacuole morphology in guard cells during stomatal closure.
Collapse
|
14
|
Diao M, Li X, Huang S. Arabidopsis AIP1-1 regulates the organization of apical actin filaments by promoting their turnover in pollen tubes. SCIENCE CHINA-LIFE SCIENCES 2019; 63:239-250. [PMID: 31240522 DOI: 10.1007/s11427-019-9532-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 04/02/2019] [Indexed: 11/24/2022]
Abstract
Apical actin filaments are highly dynamic structures that are crucial for rapid pollen tube growth, but the mechanisms regulating their dynamics and spatial organization remain incompletely understood. We here identify that AtAIP1-1 is important for regulating the turnover and organization of apical actin filaments in pollen tubes. AtAIP1-1 is distributed uniformly in the pollen tube and loss of function of AtAIP1-1 affects the organization of the actin cytoskeleton in the pollen tube. Specifically, actin filaments became disorganized within the apical region of aip1-1 pollen tubes. Consistent with the role of apical actin filaments in spatially restricting vesicles in pollen tubes, the apical region occupied by vesicles becomes enlarged in aip1-1 pollen tubes compared to WT. Using ADF1 as a representative actin-depolymerizing factor, we demonstrate that AtAIP1-1 enhances ADF1-mediated actin depolymerization and filament severing in vitro, although AtAIP1-1 alone does not have an obvious effect on actin assembly and disassembly. The dynamics of apical actin filaments are reduced in aip1-1 pollen tubes compared to WT. Our study suggests that AtAIP1-1 works together with ADF to act as a module in regulating the dynamics of apical actin filaments to facilitate the construction of the unique "apical actin structure" in the pollen tube.
Collapse
Affiliation(s)
- Min Diao
- Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China
- iHuman Institute, Shanghai Tech University, Shanghai, 201210, China
| | - Xin Li
- Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Shanjin Huang
- Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing, 100084, China.
| |
Collapse
|
15
|
Tolmie F, Poulet A, McKenna J, Sassmann S, Graumann K, Deeks M, Runions J. The cell wall of Arabidopsis thaliana influences actin network dynamics. JOURNAL OF EXPERIMENTAL BOTANY 2017; 68:4517-4527. [PMID: 28981774 DOI: 10.1093/jxb/erx269] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In plant cells, molecular connections link the cell wall-plasma membrane-actin cytoskeleton to form a continuum. It is hypothesized that the cell wall provides stable anchor points around which the actin cytoskeleton remodels. Here we use live cell imaging of fluorescently labelled marker proteins to quantify the organization and dynamics of the actin cytoskeleton and to determine the impact of disrupting connections within the continuum. Labelling of the actin cytoskeleton with green fluorescent protein (GFP)-fimbrin actin-binding domain 2 (FABD2) resulted in a network composed of fine filaments and thicker bundles that appeared as a highly dynamic remodelling meshwork. This differed substantially from the GFP-Lifeact-labelled network that appeared much more sparse with thick bundles that underwent 'simple movement', in which the bundles slightly change position, but in such a manner that the structure of the network was not substantially altered during the time of observation. Label-dependent differences in actin network morphology and remodelling necessitated development of two new image analysis techniques. The first of these, 'pairwise image subtraction', was applied to measurement of the more rapidly remodelling actin network labelled with GFP-FABD2, while the second, 'cumulative fluorescence intensity', was used to measure bulk remodelling of the actin cytoskeleton when labelled with GFP-Lifeact. In each case, these analysis techniques show that the actin cytoskeleton has a decreased rate of bulk remodelling when the cell wall-plasma membrane-actin continuum is disrupted either by plasmolysis or with isoxaben, a drug that specifically inhibits cellulose deposition. Changes in the rate of actin remodelling also affect its functionality, as observed by alteration in Golgi body motility.
Collapse
Affiliation(s)
- Frances Tolmie
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington Campus, Oxford OX3 0BP, UK
| | - Axel Poulet
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington Campus, Oxford OX3 0BP, UK
| | - Joseph McKenna
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington Campus, Oxford OX3 0BP, UK
| | - Stefan Sassmann
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - Katja Graumann
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington Campus, Oxford OX3 0BP, UK
| | - Michael Deeks
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QD, UK
| | - John Runions
- Department of Biological and Medical Sciences, Oxford Brookes University, Headington Campus, Oxford OX3 0BP, UK
| |
Collapse
|
16
|
Schwebach CL, Agrawal R, Lindert S, Kudryashova E, Kudryashov DS. The Roles of Actin-Binding Domains 1 and 2 in the Calcium-Dependent Regulation of Actin Filament Bundling by Human Plastins. J Mol Biol 2017; 429:2490-2508. [PMID: 28694070 DOI: 10.1016/j.jmb.2017.06.021] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 06/30/2017] [Accepted: 06/30/2017] [Indexed: 01/04/2023]
Abstract
The actin cytoskeleton is a complex network controlled by a vast array of intricately regulated actin-binding proteins. Human plastins (PLS1, PLS2, and PLS3) are evolutionary conserved proteins that non-covalently crosslink actin filaments into tight bundles. Through stabilization of such bundles, plastins contribute, in an isoform-specific manner, to the formation of kidney and intestinal microvilli, inner ear stereocilia, immune synapses, endocytic patches, adhesion contacts, and invadosomes of immune and cancer cells. All plastins comprise an N-terminal Ca2+-binding regulatory headpiece domain followed by two actin-binding domains (ABD1 and ABD2). Actin bundling occurs due to simultaneous binding of both ABDs to separate actin filaments. Bundling is negatively regulated by Ca2+, but the mechanism of this inhibition remains unknown. In this study, we found that the bundling abilities of PLS1 and PLS2 were similarly sensitive to Ca2+ (pCa50 ~6.4), whereas PLS3 was less sensitive (pCa50 ~5.9). At the same time, all three isoforms bound to F-actin in a Ca2+-independent manner, suggesting that binding of only one of the ABDs is inhibited by Ca2+. Using limited proteolysis and mass spectrometry, we found that in the presence of Ca2+ the EF-hands of human plastins bound to an immediately adjacent sequence homologous to canonical calmodulin-binding peptides. Furthermore, our data from differential centrifugation, Förster resonance energy transfer, native electrophoresis, and chemical crosslinking suggest that Ca2+ does not affect ABD1 but inhibits the ability of ABD2 to interact with actin. A structural mechanism of signal transmission from Ca2+ to ABD2 through EF-hands remains to be established.
Collapse
Affiliation(s)
- Christopher L Schwebach
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Molecular, Cellular, and Developmental Biology Program, The Ohio State University, Columbus, OH 43210, USA
| | - Richa Agrawal
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Steffen Lindert
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Elena Kudryashova
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
| | - Dmitri S Kudryashov
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA; Molecular, Cellular, and Developmental Biology Program, The Ohio State University, Columbus, OH 43210, USA.
| |
Collapse
|
17
|
Hensel N, Claus P. The Actin Cytoskeleton in SMA and ALS: How Does It Contribute to Motoneuron Degeneration? Neuroscientist 2017; 24:54-72. [PMID: 28459188 DOI: 10.1177/1073858417705059] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA) are neurodegenerative diseases with overlapping clinical phenotypes based on impaired motoneuron function. However, the pathomechanisms of both diseases are largely unknown, and it is still unclear whether they converge on the molecular level. SMA is a monogenic disease caused by low levels of functional Survival of Motoneuron (SMN) protein, whereas ALS involves multiple genes as well as environmental factors. Recent evidence argues for involvement of actin regulation as a causative and dysregulated process in both diseases. ALS-causing mutations in the actin-binding protein profilin-1 as well as the ability of the SMN protein to directly bind to profilins argue in favor of a common molecular mechanism involving the actin cytoskeleton. Profilins are major regulat ors of actin-dynamics being involved in multiple neuronal motility and transport processes as well as modulation of synaptic functions that are impaired in models of both motoneuron diseases. In this article, we review the current literature in SMA and ALS research with a focus on the actin cytoskeleton. We propose a common molecular mechanism that explains the degeneration of motoneurons for SMA and some cases of ALS.
Collapse
Affiliation(s)
- Niko Hensel
- 1 Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany.,2 Niedersachsen Network on Neuroinfectiology (N-RENNT), Hannover, Germany
| | - Peter Claus
- 1 Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany.,2 Niedersachsen Network on Neuroinfectiology (N-RENNT), Hannover, Germany.,3 Center for Systems Neuroscience (ZSN), Hannover, Germany
| |
Collapse
|
18
|
Yang Y, Zhang Y, Li WJ, Jiang Y, Zhu Z, Hu H, Li W, Wu JW, Wang ZX, Dong MQ, Huang S, Ou G. Spectraplakin Induces Positive Feedback between Fusogens and the Actin Cytoskeleton to Promote Cell-Cell Fusion. Dev Cell 2017; 41:107-120.e4. [DOI: 10.1016/j.devcel.2017.03.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 01/18/2017] [Accepted: 03/10/2017] [Indexed: 10/25/2022]
|
19
|
Wabnitz G, Balta E, Samstag Y. L-plastin regulates the stability of the immune synapse of naive and effector T-cells. Adv Biol Regul 2017; 63:107-114. [PMID: 27720134 DOI: 10.1016/j.jbior.2016.09.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 09/22/2016] [Accepted: 09/25/2016] [Indexed: 06/06/2023]
Abstract
T-cells need to be tightly regulated during their activation and effector phase to assure an appropriate defence against cancer or pathogens and - vice versa - to avoid autoimmune reactions. Regulatory signals are provided via the immune synapse between T-cells and antigen-presenting cells (APCs) or target cells. The stability and kinetics of immune synapse formation is critical for proper T-cell functions. It requires dynamic rearrangements of the actin cytoskeleton necessary for organized spatio-temporal redistribution of receptors and adhesion molecules. We identified glucocorticoid-sensitive phosphorylation of serine 5 on the actin-bundling protein L-plastin as one important signalling event for this regulation. Using imaging flow cytometry as well as confocal and super-resolution microscopy we showed that L-plastin relocalizes to the immune synapse upon antigen encounter, where it associates with the β2-subunit of LFA-1 (CD11a/CD18). Interfering with L-plastin expression or activation leads to a defective LFA-1 recruitment and unstable T-cell/APC contacts. Consequently, the lack of L-plastin diminishes T-cell activation, proliferation and proximal effector responses such as cytokine production. On the other hand, a pro-oxidative milieu leads to prolonged activation of L-plastin resulting in a stronger enrichment of LFA-1 in the cytolytic immune synapse. Concomitant stabilization of conjugates formed by cytotoxic T-cells (CTLs) and their target cells impairs the ability of CTLs to kill more than one target cells (serial killing), which de facto leads to a downregulation of T-cell cytotoxicity. Together, we demonstrate that activation and spacial distribution of L-plastin regulates the maturation and stability of activating and cytolytic immune synapses important for T-cell activation and effector functions.
Collapse
Affiliation(s)
- Guido Wabnitz
- Institute of Immunology, Section Molecular Immunology, Ruprecht-Karls-University Heidelberg, Im Neuenheimer Feld 305, D-69120 Heidelberg, Germany.
| | - Emre Balta
- Institute of Immunology, Section Molecular Immunology, Ruprecht-Karls-University Heidelberg, Im Neuenheimer Feld 305, D-69120 Heidelberg, Germany
| | - Yvonne Samstag
- Institute of Immunology, Section Molecular Immunology, Ruprecht-Karls-University Heidelberg, Im Neuenheimer Feld 305, D-69120 Heidelberg, Germany
| |
Collapse
|
20
|
Zhang R, Chang M, Zhang M, Wu Y, Qu X, Huang S. The Structurally Plastic CH2 Domain Is Linked to Distinct Functions of Fimbrins/Plastins. J Biol Chem 2016; 291:17881-96. [PMID: 27261463 DOI: 10.1074/jbc.m116.730069] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Indexed: 01/08/2023] Open
Abstract
Fimbrins/plastins have been implicated in the generation of distinct actin structures, which are linked to different cellular processes. Historically, fimbrins/plastins were mainly considered as generating tight actin bundles. Here, we demonstrate that different members of the fimbrin/plastin family have diverged biochemically during evolution to generate either tight actin bundles or loose networks with distinct biochemical and biophysical properties. Using the phylogenetically and functionally distinct Arabidopsis fimbrins FIM4 and FIM5 we found that FIM4 generates both actin bundles and cross-linked actin filaments, whereas FIM5 only generates actin bundles. The distinct functions of FIM4 and FIM5 are clearly observed at single-filament resolution. Domain swapping experiments showed that cooperation between the conformationally plastic calponin-homology domain 2 (CH2) and the N-terminal headpiece determines the function of the full-length protein. Our study suggests that the structural plasticity of fimbrins/plastins has biologically meaningful consequences, and provides novel insights into the structure-function relationship of fimbrins/plastins as well as shedding light on how cells generate distinct actin structures.
Collapse
Affiliation(s)
- Ruihui Zhang
- From the Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, the University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ming Chang
- the Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084
| | - Meng Zhang
- From the Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, the University of Chinese Academy of Sciences, Beijing 100049, China
| | - Youjun Wu
- From the Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093
| | - Xiaolu Qu
- the Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, the Tsinghua-Peking Joint Center for Life Sciences, Beijing 100084, and
| | - Shanjin Huang
- From the Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, the Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084,
| |
Collapse
|
21
|
Zhao S, Jiang Y, Zhao Y, Huang S, Yuan M, Zhao Y, Guo Y. CASEIN KINASE1-LIKE PROTEIN2 Regulates Actin Filament Stability and Stomatal Closure via Phosphorylation of Actin Depolymerizing Factor. THE PLANT CELL 2016; 28:1422-39. [PMID: 27268429 PMCID: PMC4944410 DOI: 10.1105/tpc.16.00078] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2016] [Accepted: 06/06/2016] [Indexed: 05/03/2023]
Abstract
The opening and closing of stomata are crucial for plant photosynthesis and transpiration. Actin filaments undergo dynamic reorganization during stomatal closure, but the underlying mechanism for this cytoskeletal reorganization remains largely unclear. In this study, we identified and characterized Arabidopsis thaliana casein kinase 1-like protein 2 (CKL2), which responds to abscisic acid (ABA) treatment and participates in ABA- and drought-induced stomatal closure. Although CKL2 does not bind to actin filaments directly and has no effect on actin assembly in vitro, it colocalizes with and stabilizes actin filaments in guard cells. Further investigation revealed that CKL2 physically interacts with and phosphorylates actin depolymerizing factor 4 (ADF4) and inhibits its activity in actin filament disassembly. During ABA-induced stomatal closure, deletion of CKL2 in Arabidopsis alters actin reorganization in stomata and renders stomatal closure less sensitive to ABA, whereas deletion of ADF4 impairs the disassembly of actin filaments and causes stomatal closure to be more sensitive to ABA Deletion of ADF4 in the ckl2 mutant partially recues its ABA-insensitive stomatal closure phenotype. Moreover, Arabidopsis ADFs from subclass I are targets of CKL2 in vitro. Thus, our results suggest that CKL2 regulates actin filament reorganization and stomatal closure mainly through phosphorylation of ADF.
Collapse
Affiliation(s)
- Shuangshuang Zhao
- Key Laboratory of Plant Stress, Life Science College, Shandong Normal University, Jinan 250014, China State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yuxiang Jiang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Science, Beijing 100093, China
| | - Yang Zhao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Shanjin Huang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Science, Beijing 100093, China Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China
| | - Ming Yuan
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yanxiu Zhao
- Key Laboratory of Plant Stress, Life Science College, Shandong Normal University, Jinan 250014, China
| | - Yan Guo
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| |
Collapse
|
22
|
Gallagher JP, Grover CE, Hu G, Wendel JF. Insights into the Ecology and Evolution of Polyploid Plants through Network Analysis. Mol Ecol 2016; 25:2644-60. [PMID: 27027619 DOI: 10.1111/mec.13626] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 03/09/2016] [Accepted: 03/22/2016] [Indexed: 12/18/2022]
Abstract
Polyploidy is a widespread phenomenon throughout eukaryotes, with important ecological and evolutionary consequences. Although genes operate as components of complex pathways and networks, polyploid changes in genes and gene expression have typically been evaluated as either individual genes or as a part of broad-scale analyses. Network analysis has been fruitful in associating genomic and other 'omic'-based changes with phenotype for many systems. In polyploid species, network analysis has the potential not only to facilitate a better understanding of the complex 'omic' underpinnings of phenotypic and ecological traits common to polyploidy, but also to provide novel insight into the interaction among duplicated genes and genomes. This adds perspective to the global patterns of expression (and other 'omic') change that accompany polyploidy and to the patterns of recruitment and/or loss of genes following polyploidization. While network analysis in polyploid species faces challenges common to other analyses of duplicated genomes, present technologies combined with thoughtful experimental design provide a powerful system to explore polyploid evolution. Here, we demonstrate the utility and potential of network analysis to questions pertaining to polyploidy with an example involving evolution of the transgressively superior cotton fibres found in polyploid Gossypium hirsutum. By combining network analysis with prior knowledge, we provide further insights into the role of profilins in fibre domestication and exemplify the potential for network analysis in polyploid species.
Collapse
Affiliation(s)
- Joseph P Gallagher
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, 50011, USA
| | - Corrinne E Grover
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, 50011, USA
| | - Guanjing Hu
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, 50011, USA
| | - Jonathan F Wendel
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA, 50011, USA
| |
Collapse
|
23
|
Zhang M, Zhang R, Qu X, Huang S. Arabidopsis FIM5 decorates apical actin filaments and regulates their organization in the pollen tube. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:3407-17. [PMID: 27117336 PMCID: PMC4892729 DOI: 10.1093/jxb/erw160] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The actin cytoskeleton is increasingly recognized as a major regulator of pollen tube growth. Actin filaments have distinct distribution patterns and dynamic properties within different regions of the pollen tube. Apical actin filaments are highly dynamic and crucial for pollen tube growth. However, how apical actin filaments are generated and properly constructed remains an open question. Here we showed that Arabidopsis fimbrin5 (FIM5) decorates filamentous structures throughout the entire tube but is apically concentrated. Apical actin structures are disorganized to different degrees in the pollen tubes of fim5 loss-of-function mutants. Further observations suggest that apical actin structures are not constructed properly because apical actin filaments cannot be maintained at the cortex of fim5 pollen tubes. Actin filaments appeared to be more curved in fim5 pollen tubes and this was confirmed by measurements showing that the convolutedness and the rate of change of convolutedness of actin filaments was significantly increased in fim5 pollen tubes. This suggests that the rigidity of the actin filaments may be compromised in fim5 pollen tubes. Further, the apical cell wall composition is altered, implying that tip-directed vesicle trafficking events are impaired in fim5 pollen tubes. Thus, we found that FIM5 decorates apical actin filaments and regulates their organization in order to drive polarized pollen tube growth.
Collapse
Affiliation(s)
- Meng Zhang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany Chinese Academy of Sciences, Beijing 100093 China University of Chinese Academy of Sciences, Beijing 100049 China
| | - Ruihui Zhang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany Chinese Academy of Sciences, Beijing 100093 China University of Chinese Academy of Sciences, Beijing 100049 China
| | - Xiaolu Qu
- Center for Plant Biology, School of Life Sciences, Tsinghua University Beijing 100084, China Tsinghua-Peking Joint Center for Life Sciences, Beijing 100084 China
| | - Shanjin Huang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany Chinese Academy of Sciences, Beijing 100093 China Center for Plant Biology, School of Life Sciences, Tsinghua University Beijing 100084, China National Center for Plant Gene Research, Beijing 100101 China
| |
Collapse
|
24
|
Biotechnological aspects of cytoskeletal regulation in plants. Biotechnol Adv 2015; 33:1043-62. [DOI: 10.1016/j.biotechadv.2015.03.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2014] [Revised: 03/03/2015] [Accepted: 03/09/2015] [Indexed: 11/23/2022]
|
25
|
14-3-3 λ protein interacts with ADF1 to regulate actin cytoskeleton dynamics in Arabidopsis. SCIENCE CHINA-LIFE SCIENCES 2015; 58:1142-50. [DOI: 10.1007/s11427-015-4897-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 03/28/2015] [Indexed: 01/15/2023]
|
26
|
Huang S, Qu X, Zhang R. Plant villins: versatile actin regulatory proteins. JOURNAL OF INTEGRATIVE PLANT BIOLOGY 2015; 57:40-9. [PMID: 25294278 DOI: 10.1111/jipb.12293] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2014] [Accepted: 10/01/2014] [Indexed: 05/03/2023]
Abstract
Regulation of actin dynamics is a central theme in cell biology that is important for different aspects of cell physiology. Villin, a member of the villin/gelsolin/fragmin superfamily of proteins, is an important regulator of actin. Villins contain six gelsolin homology domains (G1-G6) and an extra headpiece domain. In contrast to their mammalian counterparts, plant villins are expressed widely, implying that plant villins play a more general role in regulating actin dynamics. Some plant villins have a defined role in modifying actin dynamics in the pollen tube; most of their in vivo activities remain to be ascertained. Recently, our understanding of the functions and mechanisms of action for plant villins has progressed rapidly, primarily due to the advent of Arabidopsis thaliana genetic approaches and imaging capabilities that can visualize actin dynamics at the single filament level in vitro and in living plant cells. In this review, we focus on discussing the biochemical activities and modes of regulation of plant villins. Here, we present current understanding of the functions of plant villins. Finally, we highlight some of the key unanswered questions regarding the functions and regulation of plant villins for future research.
Collapse
Affiliation(s)
- Shanjin Huang
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, the Chinese Academy of Sciences, Beijing, 100093, China
| | | | | |
Collapse
|
27
|
Park JI, Ahmed NU, Jung HJ, Arasan SKT, Chung MY, Cho YG, Watanabe M, Nou IS. Identification and characterization of LIM gene family in Brassica rapa. BMC Genomics 2014; 15:641. [PMID: 25086651 PMCID: PMC4246497 DOI: 10.1186/1471-2164-15-641] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Accepted: 07/24/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND LIM (Lin-11, Isl-1 and Mec-3 domains) genes have been reported to trigger the formation of actin bundles, a major higher-order cytoskeletal assembly, in higher plants; however, the stress resistance related functions of these genes are still not well known. In this study, we collected 22 LIM genes designated as Brassica rapa LIM (BrLIM) from the Brassica database, analyzed the sequences, compared them with LIM genes of other plants and analyzed their expression after applying biotic and abiotic stresses in Chinese cabbage. RESULTS Upon sequence analysis these genes were confirmed as LIM genes and found to have a high degree of homology with LIM genes of other species. These genes showed distinct clusters when compared to other recognized LIM proteins upon phylogenetic analysis. Additionally, organ specific expression of these genes was observed in Chinese cabbage plants, with BrPLIM2a, b, c, BrDAR1, BrPLIM2e, f and g only being expressed in flower buds. Furthermore, the expression of these genes (except for BrDAR1 and BrPLIM2e) was high in the early flowering stages. The remaining genes were expressed in almost all organs tested. All BrDAR genes showed higher expression in flower buds compared to other organs. These organ specific expressions were clearly correlated with the phylogenetic grouping. In addition, BrWLIM2c and BrDAR4 responded to Fusarium oxysporum f. sp. conglutinans infection, while commonly two BrDARs and eight BrLIMs responded to cold, ABA and pH (pH5, pH7 and pH9) stress treatments in Chinese cabbage plants. CONCLUSION Taken together, the results of this study indicate that BrLIM and BrDAR genes may be involved in resistance against biotic and abiotic stresses in Brassica.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | - Ill-Sup Nou
- Department of Horticulture, Sunchon National University, 255 Jungangno, Suncheon, Jeonnam 540-950, Republic of Korea.
| |
Collapse
|
28
|
Lyon AN, Pineda RH, Hao LT, Kudryashova E, Kudryashov DS, Beattie CE. Calcium binding is essential for plastin 3 function in Smn-deficient motoneurons. Hum Mol Genet 2013; 23:1990-2004. [PMID: 24271012 DOI: 10.1093/hmg/ddt595] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The actin-binding and bundling protein, plastin 3 (PLS3), was identified as a protective modifier of spinal muscular atrophy (SMA) in some patient populations and as a disease modifier in animal models of SMA. How it functions in this process, however, is not known. Because PLS3 is an actin-binding/bundling protein, we hypothesized it would likely act via modification of the actin cytoskeleton in axons and neuromuscular junctions to protect motoneurons in SMA. To test this, we examined the ability of other known actin cytoskeleton organizing proteins to modify motor axon outgrowth phenotypes in an smn morphant zebrafish model of SMA. While PLS3 can fully compensate for low levels of smn, cofilin 1, profilin 2 and α-actinin 1 did not affect smn morphant motor axon outgrowth. To determine how PLS3 functions in SMA, we generated deletion constructs of conserved PLS3 structural domains. The EF hands were essential for PLS3 rescue of smn morphant phenotypes, and mutation of the Ca(2+)-binding residues within the EF hands resulted in a complete loss of PLS3 rescue. These results indicate that Ca(2+) regulation is essential for the function of PLS3 in motor axons. Remarkably, PLS3 mutants lacking both actin-binding domains were still able to rescue motor axons in smn morphants, although not as well as full-length PLS3. Therefore, PLS3 function in this process may have an actin-independent component.
Collapse
Affiliation(s)
- Alison N Lyon
- Department of Neuroscience, The Ohio State University, 132 Rightmire Hall, 1060 Carmack Rd, Columbus, OH 43210, USA and
| | | | | | | | | | | |
Collapse
|
29
|
Jia H, Li J, Zhu J, Fan T, Qian D, Zhou Y, Wang J, Ren H, Xiang Y, An L. Arabidopsis CROLIN1, a novel plant actin-binding protein, functions in cross-linking and stabilizing actin filaments. J Biol Chem 2013; 288:32277-32288. [PMID: 24072702 DOI: 10.1074/jbc.m113.483594] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Higher order actin filament structures are necessary for cytoplasmic streaming, organelle movement, and other physiological processes. However, the mechanism by which the higher order cytoskeleton is formed in plants remains unknown. In this study, we identified a novel actin-cross-linking protein family (named CROLIN) that is well conserved only in the plant kingdom. There are six isovariants of CROLIN in the Arabidopsis genome, with CROLIN1 specifically expressed in pollen. In vitro biochemical analyses showed that CROLIN1 is a novel actin-cross-linking protein with binding and stabilizing activities. Remarkably, CROLIN1 can cross-link actin bundles into actin networks. CROLIN1 loss of function induces pollen germination and pollen tube growth hypersensitive to latrunculin B. All of these results demonstrate that CROLIN1 may play an important role in stabilizing and remodeling actin filaments by binding to and cross-linking actin filaments.
Collapse
Affiliation(s)
- Honglei Jia
- From the Key Laboratory of Cell Activities and Stress Adaptations of the Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Jisheng Li
- From the Key Laboratory of Cell Activities and Stress Adaptations of the Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Jingen Zhu
- From the Key Laboratory of Cell Activities and Stress Adaptations of the Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Tingting Fan
- From the Key Laboratory of Cell Activities and Stress Adaptations of the Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Dong Qian
- From the Key Laboratory of Cell Activities and Stress Adaptations of the Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Yuelong Zhou
- From the Key Laboratory of Cell Activities and Stress Adaptations of the Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
| | - Jiaojiao Wang
- the Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education and College of Life Science, Beijing Normal University, Beijing 100875, China
| | - Haiyun Ren
- the Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education and College of Life Science, Beijing Normal University, Beijing 100875, China
| | - Yun Xiang
- From the Key Laboratory of Cell Activities and Stress Adaptations of the Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
| | - Lizhe An
- From the Key Laboratory of Cell Activities and Stress Adaptations of the Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
| |
Collapse
|
30
|
Li Y, Jiang J, Li L, Wang XL, Wang NN, Li DD, Li XB. A cotton LIM domain-containing protein (GhWLIM5) is involved in bundling actin filaments. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2013; 66:34-40. [PMID: 23466745 DOI: 10.1016/j.plaphy.2013.01.018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Accepted: 01/18/2013] [Indexed: 06/01/2023]
Abstract
LIM-domain proteins play important roles in cellular processes in eukaryotes. In this study, a LIM protein gene, GhWLIM5, was identified in cotton. Quantitative RT-PCR analysis showed that GhWLIM5 was expressed widely in different cotton tissues and had a peak in expression during fiber elongation. GFP fluorescence assay revealed that cotton cells expressing GhWLIM5:eGFP fusion gene displayed a network distribution of eGFP fluorescence, suggesting that GhWLIM5 protein is mainly localized to the cell cytoskeleton. When GhWLIM5:eGFP transformed cells were stained with rhodamine-phalloidin there was consistent overlap in eGFP and rhodamine-palloidin signals, demonstrating that GhWLIM5 protein is colocalized with the F-actin cytoskeleton. In addition, high-speed cosedimentation assay verified that GhWLIM5 directly bound actin filaments, while low cosedimentation assay and microscopic observation indicated that GhWLIM5 bundled F-actin in vitro. Increasing amounts of GhWLIM5 protein were able to protect F-actin from depolymerization in vitro in the presence of Lat B (an F-actin depolymerizer). Our results contribute to a better understanding of the biochemical role of GhWLIM5 in modulating the dynamic F-actin network in cotton.
Collapse
Affiliation(s)
- Yang Li
- Hubei Key Laboratory of Genetic Regulation and Integrative Biology, College of Life Sciences, Central China Normal University, Wuhan 430079, China
| | | | | | | | | | | | | |
Collapse
|
31
|
Kusdian G, Woehle C, Martin WF, Gould SB. The actin-based machinery of Trichomonas vaginalis mediates flagellate-amoeboid transition and migration across host tissue. Cell Microbiol 2013; 15:1707-21. [PMID: 23530917 DOI: 10.1111/cmi.12144] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 03/16/2013] [Accepted: 03/20/2013] [Indexed: 11/28/2022]
Abstract
Trichomonas vaginalis is the most widespread non-viral pathogen of the human urogenital tract, infecting ∼ 3% of the world's population annually. At the onset of infection the protist changes morphology within minutes: the flagellated free-swimming cell converts into the amoeboid-adherent stage. The molecular machinery of this process is not well studied, but is thought to involve actin reorganization. We have characterized amoeboid transition, focusing in particular on TvFim1, the only expressed protein of the fimbrin family in Trichomonas. Addition of TvFim1 to actin polymerization assays increases the speed of actin filament assembly and results in bundling of F-actin in a parallel and anti-parallel manner. Upon contact with vaginal epithelial cells, the otherwise diffuse localization of actin and TvFim1 changes dramatically. In the amoeboid TvFim1 associates with fibrous actin bundles and concentrates at protrusive structures opposing the trailing ends of the gliding amoeboid form and rapidly redistributes together with actin to form distinct clusters. Live cell imaging demonstrates that Trichomonas amoeboid stages do not just adhere to host tissue, rather they actively migrate across human epithelial cells. They do so in a concerted manner, with an average speed of 20 μm min(-1) and often using their flagella and apical tip as the leading edge.
Collapse
Affiliation(s)
- Gary Kusdian
- Institute for Molecular Evolution, Heinrich-Heine-University Düsseldorf, 40225, Düsseldorf, Germany
| | | | | | | |
Collapse
|
32
|
Shi M, Xie Y, Zheng Y, Wang J, Su Y, Yang Q, Huang S. Oryza sativa actin-interacting protein 1 is required for rice growth by promoting actin turnover. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 73:747-60. [PMID: 23134061 DOI: 10.1111/tpj.12065] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2012] [Revised: 10/18/2012] [Accepted: 11/01/2012] [Indexed: 05/03/2023]
Abstract
Rapid actin turnover is essential for numerous actin-based processes. However, how it is precisely regulated remains poorly understood. Actin-interacting protein 1 (AIP1) has been shown to be an important factor by acting coordinately with actin-depolymerizing factor (ADF)/cofilin in promoting actin depolymerization, the rate-limiting factor in actin turnover. However, the molecular mechanism by which AIP1 promotes actin turnover remains largely unknown in plants. Here, we provide a demonstration that AIP1 promotes actin turnover, which is required for optimal growth of rice plants. Specific down-regulation of OsAIP1 increased the level of filamentous actin and reduced actin turnover, whereas over-expression of OsAIP1 induced fragmentation and depolymerization of actin filaments and enhanced actin turnover. In vitro biochemical characterization showed that, although OsAIP1 alone does not affect actin dynamics, it enhances ADF-mediated actin depolymerization. It also caps the filament barbed end in the presence of ADF, but the capping activity is not required for their coordinated action. Real-time visualization of single filament dynamics showed that OsAIP1 enhanced ADF-mediated severing and dissociation of pointed end subunits. Consistent with this, the filament severing frequency and subunit off-rate were enhanced in OsAIP1 over-expressors but decreased in RNAi protoplasts. Importantly, OsAIP1 acts coordinately with ADF and profilin to induce massive net actin depolymerization, indicating that AIP1 plays a major role in the turnover of actin, which is required to optimize F-actin levels in plants.
Collapse
Affiliation(s)
- Meng Shi
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | | | | | | | | | | | | |
Collapse
|
33
|
Miyakawa T, Shinomiya H, Yumoto F, Miyauchi Y, Tanaka H, Ojima T, Kato YS, Tanokura M. Different Ca²⁺-sensitivities between the EF-hands of T- and L-plastins. Biochem Biophys Res Commun 2012; 429:137-41. [PMID: 23142595 DOI: 10.1016/j.bbrc.2012.10.126] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2012] [Accepted: 10/28/2012] [Indexed: 10/27/2022]
Abstract
Plastins are Ca(2+)-regulated actin-bundling proteins, and essential for developing and stabilizing actin cytoskeletons. T-plastin is expressed in epithelial and mesenchymal cells of solid tissues, whereas L-plastin is expressed in mobile cells such as hemopoietic cell lineages and cancer cells. Using various spectroscopic methods, gel-filtration chromatography, and isothermal titration calorimetry, we here demonstrate that the EF-hand motifs of both T- and L-plastin change their structures in response to Ca(2+), but the sensitivity to Ca(2+) is lower in T-plastin than in L-plastin. These results suggest that T-plastin is suitable for maintaining static cytoskeletons, whereas L-plastin is suitable for dynamic rearrangement of cytoskeletons.
Collapse
Affiliation(s)
- Takuya Miyakawa
- Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
| | | | | | | | | | | | | | | |
Collapse
|
34
|
Bao C, Wang J, Zhang R, Zhang B, Zhang H, Zhou Y, Huang S. Arabidopsis VILLIN2 and VILLIN3 act redundantly in sclerenchyma development via bundling of actin filaments. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 71:962-75. [PMID: 22563899 DOI: 10.1111/j.1365-313x.2012.05044.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The organization of the actin cytoskeleton has been implicated in sclerenchyma development. However, the molecular mechanisms linking the actin cytoskeleton to this process remain poorly understood. In particular, there have been no studies showing that direct genetic manipulation of the actin cytoskeleton affects sclerenchyma development. Villins belong to the villin/gelsolin/fragmin superfamily and are versatile actin-modifying proteins. Several recent studies have implicated villins in tip growth of single cells, but how villins act in multicellular plant development remains largely unknown. Here, we found that two closely related villin isovariants from Arabidopsis, VLN2 and VLN3, act redundantly in sclerenchyma development. Detailed analysis of cross-sections from inflorescence stems of vln2 vln3 double mutant plants revealed a reduction in stem size and in the number of vascular bundles; however, no defects in synthesis of the secondary cell wall were detected. Surprisingly, the vln2 vln3 double mutation did not affect cell elongation of inter-fascicular fibers. Biochemical analyses showed that recombinant VLN2 was able to cap, sever and bundle actin filaments, similar to VLN3. Consistent with these biochemical activities, loss of function of VLN2 and VLN3 resulted in a decrease in the amount of F-actin and actin bundles in plant cells. Collectively, our findings demonstrate that VLN2 and VLN3 act redundantly in sclerenchyma development via bundling of actin filaments.
Collapse
Affiliation(s)
- Chanchan Bao
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | | | | | | | | | | | | |
Collapse
|
35
|
Thomas C. Bundling actin filaments from membranes: some novel players. FRONTIERS IN PLANT SCIENCE 2012; 3:188. [PMID: 22936939 PMCID: PMC3426786 DOI: 10.3389/fpls.2012.00188] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Accepted: 08/01/2012] [Indexed: 05/04/2023]
Abstract
Progress in live-cell imaging of the cytoskeleton has significantly extended our knowledge about the organization and dynamics of actin filaments near the plasma membrane of plant cells. Noticeably, two populations of filamentous structures can be distinguished. On the one hand, fine actin filaments which exhibit an extremely dynamic behavior basically characterized by fast polymerization and prolific severing events, a process referred to as actin stochastic dynamics. On the other hand, thick actin bundles which are composed of several filaments and which are comparatively more stable although they constantly remodel as well. There is evidence that the actin cytoskeleton plays critical roles in trafficking and signaling at both the cell cortex and organelle periphery but the exact contribution of actin bundles remains unclear. A common view is that actin bundles provide the long-distance tracks used by myosin motors to deliver their cargo to growing regions and accordingly play a particularly important role in cell polarization. However, several studies support that actin bundles are more than simple passive highways and display multiple and dynamic roles in the regulation of many processes, such as cell elongation, polar auxin transport, stomatal and chloroplast movement, and defense against pathogens. The list of identified plant actin-bundling proteins is ever expanding, supporting that plant cells shape structurally and functionally different actin bundles. Here I review the most recently characterized actin-bundling proteins, with a particular focus on those potentially relevant to membrane trafficking and/or signaling.
Collapse
Affiliation(s)
- Clément Thomas
- Laboratory of Molecular and Cellular Oncology, Department of Oncology, Public Research Centre for Health (CRP-Santé)Luxembourg, Luxembourg
| |
Collapse
|
36
|
van der Honing HS, Kieft H, Emons AMC, Ketelaar T. Arabidopsis VILLIN2 and VILLIN3 are required for the generation of thick actin filament bundles and for directional organ growth. PLANT PHYSIOLOGY 2012; 158:1426-38. [PMID: 22209875 PMCID: PMC3291277 DOI: 10.1104/pp.111.192385] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 12/21/2011] [Indexed: 05/18/2023]
Abstract
In plant cells, actin filament bundles serve as tracks for myosin-dependent organelle movement and play a role in the organization of the cytoplasm. Although virtually all plant cells contain actin filament bundles, the role of the different actin-bundling proteins remains largely unknown. In this study, we investigated the role of the actin-bundling protein villin in Arabidopsis (Arabidopsis thaliana). We used Arabidopsis T-DNA insertion lines to generate a double mutant in which VILLIN2 (VLN2) and VLN3 transcripts are truncated. Leaves, stems, siliques, and roots of vln2 vln3 double mutant plants are twisted, which is caused by local differences in cell length. Microscopy analysis of the actin cytoskeleton showed that in these double mutant plants, thin actin filament bundles are more abundant while thick actin filament bundles are virtually absent. In contrast to full-length VLN3, truncated VLN3 lacking the headpiece region does not rescue the phenotype of the vln2 vln3 double mutant. Our results show that villin is involved in the generation of thick actin filament bundles in several cell types and suggest that these bundles are involved in the regulation of coordinated cell expansion.
Collapse
Affiliation(s)
- Hannie S. van der Honing
- Laboratory of Cell Biology, Wageningen University, 6708 PB Wageningen, The Netherlands (H.S.v.d.H., H.K., A.M.C.E., T.K.); and Department of Biomolecular Systems, Stichting voor Fundamenteel Onderzoek der Materie Institute for Atomic and Molecular Physics, 1098 SG Amsterdam, The Netherlands (A.M.C.E.)
| | - Henk Kieft
- Laboratory of Cell Biology, Wageningen University, 6708 PB Wageningen, The Netherlands (H.S.v.d.H., H.K., A.M.C.E., T.K.); and Department of Biomolecular Systems, Stichting voor Fundamenteel Onderzoek der Materie Institute for Atomic and Molecular Physics, 1098 SG Amsterdam, The Netherlands (A.M.C.E.)
| | - Anne Mie C. Emons
- Laboratory of Cell Biology, Wageningen University, 6708 PB Wageningen, The Netherlands (H.S.v.d.H., H.K., A.M.C.E., T.K.); and Department of Biomolecular Systems, Stichting voor Fundamenteel Onderzoek der Materie Institute for Atomic and Molecular Physics, 1098 SG Amsterdam, The Netherlands (A.M.C.E.)
| | - Tijs Ketelaar
- Laboratory of Cell Biology, Wageningen University, 6708 PB Wageningen, The Netherlands (H.S.v.d.H., H.K., A.M.C.E., T.K.); and Department of Biomolecular Systems, Stichting voor Fundamenteel Onderzoek der Materie Institute for Atomic and Molecular Physics, 1098 SG Amsterdam, The Netherlands (A.M.C.E.)
| |
Collapse
|
37
|
Zhang W, Zhao Y, Guo Y, Ye K. Plant actin-binding protein SCAB1 is dimeric actin cross-linker with atypical pleckstrin homology domain. J Biol Chem 2012; 287:11981-90. [PMID: 22356912 DOI: 10.1074/jbc.m111.338525] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
SCAB1 is a novel plant-specific actin-binding protein that binds, bundles, and stabilizes actin filaments and regulates stomatal movement. Here, we dissected the structure and function of SCAB1 by structural and biochemical approaches. We show that SCAB1 is composed of an actin-binding domain, two coiled-coil (CC) domains, and a fused immunoglobulin and pleckstrin homology (Ig-PH) domain. We determined crystal structures for the CC1 and Ig-PH domains at 1.9 and 1.7 Å resolution, respectively. The CC1 domain adopts an antiparallel helical hairpin that further dimerizes into a four-helix bundle. The CC2 domain also mediates dimerization. At least one of the coiled coils is required for actin binding, indicating that SCAB1 is a bivalent actin cross-linker. The key residues required for actin binding were identified. The PH domain lacks a canonical basic phosphoinositide-binding pocket but can bind weakly to inositol phosphates via a basic surface patch, implying the involvement of inositol signaling in SCAB1 regulation. Our results provide novel insights into the functional organization of SCAB1.
Collapse
Affiliation(s)
- Wei Zhang
- College of Biological Sciences, China Agricultural University, Beijing 10019, China
| | | | | | | |
Collapse
|
38
|
Poulter NS, Bosch M, Franklin-Tong VE. Proteins implicated in mediating self-incompatibility-induced alterations to the actin cytoskeleton of Papaver pollen. ANNALS OF BOTANY 2011; 108:659-75. [PMID: 21320881 PMCID: PMC3170148 DOI: 10.1093/aob/mcr022] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Accepted: 01/04/2011] [Indexed: 05/20/2023]
Abstract
BACKGROUND AND AIMS Sexual reproduction in angiosperms involves a network of signalling and interactions between pollen and pistil. To promote out-breeding, an additional layer of interactions, involving self-incompatibility (SI), is used to prevent self-fertilization. SI is generally controlled by the S-locus, and comprises allelic pollen and pistil S-determinants. This provides the basis of recognition, and consequent rejection, of incompatible pollen. In Papaver rhoeas, SI involves interaction of pistil PrsS and pollen PrpS, triggering a Ca(2+)-dependent signalling network. This results in rapid and distinctive alterations to both the actin and microtubule cytoskeleton being triggered in 'self' pollen. Some of these alterations are implicated in mediating programmed cell death, involving activation of several caspase-like proteases. SCOPE Here we review and discuss our current understanding of the cytoskeletal alterations induced in incompatible pollen during SI and their relationship with programmed cell death. We focus on data relating to the formation of F-actin punctate foci, which have, to date, not been well characterized. The identification of two actin-binding proteins that interact with these structures are reviewed. Using an approach that enriched for F-actin from SI-induced pollen tubes using affinity purification followed by mass spectrometry, further proteins were identified as putative interactors with the F-actin foci in an SI situation. KEY RESULTS Previously two important actin-binding proteins, CAP and ADF, had been identified whose localization altered with SI, both showing co-localization with the F-actin punctate foci based on immunolocalization studies. Further analysis has identified differences between proteins associated with F-actin from SI-induced pollen samples and those associated with F-actin in untreated pollen. This provides candidate proteins implicated in either the formation or stabilization of the punctate actin structures formed during SI. CONCLUSIONS This review brings together for the first time, our current understanding of proteins and events involved in SI-induced signalling to the actin cytoskeleton in incompatible Papaver pollen.
Collapse
|
39
|
Zhao Y, Zhao S, Mao T, Qu X, Cao W, Zhang L, Zhang W, He L, Li S, Ren S, Zhao J, Zhu G, Huang S, Ye K, Yuan M, Guo Y. The plant-specific actin binding protein SCAB1 stabilizes actin filaments and regulates stomatal movement in Arabidopsis. THE PLANT CELL 2011; 23:2314-30. [PMID: 21719691 PMCID: PMC3160031 DOI: 10.1105/tpc.111.086546] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 05/28/2011] [Accepted: 06/10/2011] [Indexed: 05/18/2023]
Abstract
Microfilament dynamics play a critical role in regulating stomatal movement; however, the molecular mechanism underlying this process is not well understood. We report here the identification and characterization of STOMATAL CLOSURE-RELATED ACTIN BINDING PROTEIN1 (SCAB1), an Arabidopsis thaliana actin binding protein. Plants lacking SCAB1 were hypersensitive to drought stress and exhibited reduced abscisic acid-, H(2)O(2)-, and CaCl(2)-regulated stomatal movement. In vitro and in vivo analyses revealed that SCAB1 binds, stabilizes, and bundles actin filaments. SCAB1 shares sequence similarity only with plant proteins and contains a previously undiscovered actin binding domain. During stomatal closure, actin filaments switched from a radial orientation in open stomata to a longitudinal orientation in closed stomata. This switch took longer in scab1 plants than in wild-type plants and was correlated with the delay in stomatal closure seen in scab1 mutants in response to drought stress. Our results suggest that SCAB1 is required for the precise regulation of actin filament reorganization during stomatal closure.
Collapse
Affiliation(s)
- Yang Zhao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
- National Institute of Biological Sciences, Beijing 102206, China
| | - Shuangshuang Zhao
- Key Laboratory of Plant Stress, Life Science College, Shandong Normal University, Jinan 250014, China
| | - Tonglin Mao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Xiaolu Qu
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Wanhong Cao
- National Institute of Biological Sciences, Beijing 102206, China
| | - Li Zhang
- National Institute of Biological Sciences, Beijing 102206, China
| | - Wei Zhang
- National Institute of Biological Sciences, Beijing 102206, China
| | - Liu He
- National Institute of Biological Sciences, Beijing 102206, China
| | - Sidi Li
- National Institute of Biological Sciences, Beijing 102206, China
| | - Sulin Ren
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Jinfeng Zhao
- National Institute of Biological Sciences, Beijing 102206, China
| | - Guoli Zhu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Shanjin Huang
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Keqiong Ye
- National Institute of Biological Sciences, Beijing 102206, China
| | - Ming Yuan
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yan Guo
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
- Address correspondence to
| |
Collapse
|
40
|
Zhang Y, Xiao Y, Du F, Cao L, Dong H, Ren H. Arabidopsis VILLIN4 is involved in root hair growth through regulating actin organization in a Ca2+-dependent manner. THE NEW PHYTOLOGIST 2011; 190:667-82. [PMID: 21275995 DOI: 10.1111/j.1469-8137.2010.03632.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
• Villin is one of the major actin filament bundling proteins in plants. The function of Arabidopsis VILLINs (AtVLNs) is still poorly understood in living cells. In this report, the biochemical activity and cellular function of AtVLN4 were examined. • The biochemical property of AtVLN4 was characterized by co-sedimentation assays, fluorescence microscopy and spectroscopy of pyrene fluorescence. The in vivo function of AtVLN4 was analysed by ectopically expressing it in tobacco pollen and examining the phenotypes of its T-DNA insertional plants. • Recombinant AtVLN4 protein exhibited multiple activities on actin, including actin filament bundling, calcium (Ca(2+))-dependent filament severing and barbed end capping. Expression of AtVLN4 in tobacco pollen induced the formation of supernumerary actin cables and reduced pollen tube growth. Loss of function of AtVLN4 resulted in slowing of root hair growth, alteration in cytoplasmic streaming routes and rate, and reduction of both axial and apical actin bundles. • Our results demonstrated that AtVLN4 is involved in root hair growth through regulating actin organization in a Ca(2+)-dependent manner.
Collapse
Affiliation(s)
- Yi Zhang
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education and College of Life Science, Beijing Normal University, Beijing, China
| | | | | | | | | | | |
Collapse
|
41
|
Du F, Ren H. Development and application of probes for labeling the actin cytoskeleton in living plant cells. PROTOPLASMA 2011; 248:239-50. [PMID: 20803158 DOI: 10.1007/s00709-010-0202-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Accepted: 08/14/2010] [Indexed: 05/15/2023]
Abstract
The actin cytoskeleton is one of the most important components of eukaryotic cytoskeletons. It participates in numerous crucial procedures of cells and has been studied by using various methods. The development and application of appropriate probes for actin visualization is the first and foremost step for functional analysis of actin in vivo. Since the actin cytoskeleton is a highly dynamic and sensitive structure, methods previously used to visualize actin often harm cells and cannot reveal the native state of the actin cytoskeleton in living cells. The development of labeling technologies for living plant cells, especially the emergence and application of green fluorescent protein-tagged actin markers, has provided new insights into the structure and function of the actin cytoskeleton in vivo. There has been a number of probes for actin labeling in living plant cells though they each present different advantages and defects. In this review, we discuss and compare those widely used methods for actin visualization and analysis.
Collapse
Affiliation(s)
- Fei Du
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Science, Beijing Normal University, Beijing, 100875, China
| | | |
Collapse
|
42
|
Day B, Henty JL, Porter KJ, Staiger CJ. The pathogen-actin connection: a platform for defense signaling in plants. ANNUAL REVIEW OF PHYTOPATHOLOGY 2011; 49:483-506. [PMID: 21495845 DOI: 10.1146/annurev-phyto-072910-095426] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The cytoskeleton, a dynamic network of cytoplasmic polymers, plays a central role in numerous fundamental processes, such as development, reproduction, and cellular responses to biotic and abiotic stimuli. As a platform for innate immune responses in mammalian cells, the actin cytoskeleton is a central component in the organization and activation of host defenses, including signaling and cellular repair. In plants, our understanding of the genetic and biochemical responses in both pathogen and host that are required for virulence and resistance has grown enormously. Additional advances in live-cell imaging of cytoskeletal dynamics have markedly altered our view of actin turnover in plants. In this review, we outline current knowledge of host resistance following pathogen perception, both in terms of the genetic interactions that mediate defense signaling, as well as the biochemical and cellular processes that are required for defense signaling.
Collapse
Affiliation(s)
- Brad Day
- Department of Plant Pathology, Michigan State University, East Lansing, Michigan 48824-1311, USA.
| | | | | | | |
Collapse
|
43
|
Intracellular Movements: Integration at the Cellular Level as Reflected in the Organization of Organelle Movements. MECHANICAL INTEGRATION OF PLANT CELLS AND PLANTS 2011. [DOI: 10.1007/978-3-642-19091-9_4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
|
44
|
Friedberg F. Single and multiple CH (calponin homology) domain containing multidomain proteins in Arabidopsis and Saccharomyces: an inventory. Mol Biol Rep 2011; 38:213-8. [PMID: 20349140 DOI: 10.1007/s11033-010-0097-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Accepted: 03/15/2010] [Indexed: 10/19/2022]
Abstract
Genes for individual domains such as CH, lim, ankyrin, PH and RhoGAP, IQ motif, Ig_FLMN, spectrin, and EF hand probably existed in early evolution before there were plants, fungi or animals so that when we examine multidomain proteins in Arabidopsis, Saccharomyces, Dictyostelium or Homo Sapiens we encounter various combinations of such domains. While all of these four species express Fimbrin and EB1, the lists of CH containing multidomain proteins, however, differ in number and in type for each of them. There was no further great increase in the number of new single domain proteins. Still many new multidomain genes evolved--but far more so in metazoans--than in plants or fungi. In both plants and fungi only singlet CH domains but no doublets (other than those forming the Fimbrin quadruplet) were incorporated. That is in these two branches one finds no alpha actinin, dystrophin or filamin even though the individual building blocks (i.e. domains such as spectrin or IG-FLMN) were available in Arabidopsis. Possibly transposons create new chimeric multidomain genes by mixing and matching genes or gene fragments.
Collapse
|
45
|
Whippo CW, Khurana P, Davis PA, DeBlasio SL, DeSloover D, Staiger CJ, Hangarter RP. THRUMIN1 is a light-regulated actin-bundling protein involved in chloroplast motility. Curr Biol 2010; 21:59-64. [PMID: 21185188 DOI: 10.1016/j.cub.2010.11.059] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 10/25/2010] [Accepted: 11/23/2010] [Indexed: 02/04/2023]
Abstract
Chloroplast movement in response to changing light conditions optimizes photosynthetic light absorption. This repositioning is stimulated by blue light perceived via the phototropin photoreceptors and is transduced to the actin cytoskeleton. Some actin-based motility systems use filament reorganizations rather than myosin-based translocations. Recent research favors the hypothesis that chloroplast movement is driven by actin reorganization at the plasma membrane, but no proteins affecting chloroplast movements have been shown to associate with both the plasma membrane and actin filaments in vivo. Here we identified THRUMIN1 as a critical link between phototropin photoreceptor activity at the plasma membrane and actin-dependent chloroplast movements. THRUMIN1 bundles filamentous actin in vitro, and it localizes to the plasma membrane and displays light- and phototropin-dependent localization to microfilaments in vivo. These results suggest that phototropin-induced actin bundling via THRUMIN1 is important for chloroplast movement. A mammalian homolog of THRUMIN1, GRXCR1, has been implicated in auditory responses and hair cell stereocilla development as a regulator of actin architecture. Studies of THRUMIN1 will help elucidate the function of this family of eukaryotic proteins.
Collapse
Affiliation(s)
- Craig W Whippo
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | | | | | | | | | | | | |
Collapse
|
46
|
Wu Y, Yan J, Zhang R, Qu X, Ren S, Chen N, Huang S. Arabidopsis FIMBRIN5, an actin bundling factor, is required for pollen germination and pollen tube growth. THE PLANT CELL 2010; 22:3745-63. [PMID: 21098731 PMCID: PMC3015131 DOI: 10.1105/tpc.110.080283] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2010] [Revised: 10/09/2010] [Accepted: 11/08/2010] [Indexed: 05/18/2023]
Abstract
Actin cables in pollen tubes serve as molecular tracks for cytoplasmic streaming and organelle movement and are formed by actin bundling factors like villins and fimbrins. However, the precise mechanisms by which actin cables are generated and maintained remain largely unknown. Fimbrins comprise a family of five members in Arabidopsis thaliana. Here, we characterized a fimbrin isoform, Arabidopsis FIMBRIN5 (FIM5). Our results show that FIM5 is required for the organization of actin cytoskeleton in pollen grains and pollen tubes, and FIM5 loss-of-function associates with a delay of pollen germination and inhibition of pollen tube growth. FIM5 decorates actin filaments throughout pollen grains and tubes. Actin filaments become redistributed in fim5 pollen grains and disorganized in fim5 pollen tubes. Specifically, actin cables protrude into the extreme tips, and their longitudinal arrangement is disrupted in the shank of fim5 pollen tubes. Consequently, the pattern and velocity of cytoplasmic streaming were altered in fim5 pollen tubes. Additionally, loss of FIM5 function rendered pollen germination and tube growth hypersensitive to the actin-depolymerizing drug latrunculin B. In vitro biochemical analyses indicated that FIM5 exhibits actin bundling activity and stabilizes actin filaments. Thus, we propose that FIM5 regulates actin dynamics and organization during pollen germination and tube growth via stabilizing actin filaments and organizing them into higher-order structures.
Collapse
Affiliation(s)
- Youjun Wu
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing 100049, China
| | - Jin Yan
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing 100049, China
| | - Ruihui Zhang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaolu Qu
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing 100049, China
| | - Sulin Ren
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing 100049, China
| | - Naizhi Chen
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Shanjin Huang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Address correspondence to
| |
Collapse
|
47
|
Papuga J, Hoffmann C, Dieterle M, Moes D, Moreau F, Tholl S, Steinmetz A, Thomas C. Arabidopsis LIM proteins: a family of actin bundlers with distinct expression patterns and modes of regulation. THE PLANT CELL 2010; 22:3034-52. [PMID: 20817848 PMCID: PMC2965535 DOI: 10.1105/tpc.110.075960] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Revised: 07/04/2010] [Accepted: 08/19/2010] [Indexed: 05/18/2023]
Abstract
Recently, a number of two LIM-domain containing proteins (LIMs) have been reported to trigger the formation of actin bundles, a major higher-order cytoskeletal assembly. Here, we analyzed the six Arabidopsis thaliana LIM proteins. Promoter-β-glucuronidase reporter studies revealed that WLIM1, WLIM2a, and WLIM2b are widely expressed, whereas PLIM2a, PLIM2b, and PLIM2c are predominantly expressed in pollen. LIM-green fluorescent protein (GFP) fusions all decorated the actin cytoskeleton and increased actin bundle thickness in transgenic plants and in vitro, although with different affinities and efficiencies. Remarkably, the activities of WLIMs were calcium and pH independent, whereas those of PLIMs were inhibited by high pH and, in the case of PLIM2c, by high [Ca(2+)]. Domain analysis showed that the C-terminal domain is key for the responsiveness of PLIM2c to pH and calcium. Regulation of LIM by pH was further analyzed in vivo by tracking GFP-WLIM1 and GFP-PLIM2c during intracellular pH modifications. Cytoplasmic alkalinization specifically promoted release of GFP-PLIM2c but not GFP-WLIM1, from filamentous actin. Consistent with these data, GFP-PLIM2c decorated long actin bundles in the pollen tube shank, a region of relatively low pH. Together, our data support a prominent role of Arabidopsis LIM proteins in the regulation of actin cytoskeleton organization and dynamics in sporophytic tissues and pollen.
Collapse
Affiliation(s)
| | | | | | | | | | | | | | - Clément Thomas
- Centre de Recherche Public-Santé, L-1526 Luxembourg, Luxembourg
| |
Collapse
|
48
|
Zhang H, Qu X, Bao C, Khurana P, Wang Q, Xie Y, Zheng Y, Chen N, Blanchoin L, Staiger CJ, Huang S. Arabidopsis VILLIN5, an actin filament bundling and severing protein, is necessary for normal pollen tube growth. THE PLANT CELL 2010; 22:2749-67. [PMID: 20807879 PMCID: PMC2947167 DOI: 10.1105/tpc.110.076257] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
A dynamic actin cytoskeleton is essential for pollen germination and tube growth. However, the molecular mechanisms underlying the organization and turnover of the actin cytoskeleton in pollen remain poorly understood. Villin plays a key role in the formation of higher-order structures from actin filaments and in the regulation of actin dynamics in eukaryotic cells. It belongs to the villin/gelsolin/fragmin superfamily of actin binding proteins and is composed of six gelsolin-homology domains at its core and a villin headpiece domain at its C terminus. Recently, several villin family members from plants have been shown to sever, cap, and bundle actin filaments in vitro. Here, we characterized a villin isovariant, Arabidopsis thaliana VILLIN5 (VLN5), that is highly and preferentially expressed in pollen. VLN5 loss-of-function retarded pollen tube growth and sensitized actin filaments in pollen grains and tubes to latrunculin B. In vitro biochemical analyses revealed that VLN5 is a typical member of the villin family and retains a full suite of activities, including barbed-end capping, filament bundling, and calcium-dependent severing. The severing activity was confirmed with time-lapse evanescent wave microscopy of individual actin filaments in vitro. We propose that VLN5 is a major regulator of actin filament stability and turnover that functions in concert with oscillatory calcium gradients in pollen and therefore plays an integral role in pollen germination and tube growth.
Collapse
Affiliation(s)
- Hua Zhang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaolu Qu
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chanchan Bao
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Parul Khurana
- Department of Biological Sciences and Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907-2064
| | - Qiannan Wang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yurong Xie
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Yiyan Zheng
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Graduate School of Chinese Academy of Sciences, Beijing, 100049, China
| | - Naizhi Chen
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
| | - Laurent Blanchoin
- Institut de Recherches en Technologie et Sciences pour le Vivant, Laboratoire de Physiologie Cellulaire Végétale, Commissariat à l’Energie Atomique/Centre National de la Recherche Scientifique/Université Joseph Fourier, F38054 Grenoble, France
| | - Christopher J. Staiger
- Department of Biological Sciences and Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907-2064
| | - Shanjin Huang
- Center for Signal Transduction and Metabolomics, Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
- Address correspondence to
| |
Collapse
|
49
|
Khurana P, Henty JL, Huang S, Staiger AM, Blanchoin L, Staiger CJ. Arabidopsis VILLIN1 and VILLIN3 have overlapping and distinct activities in actin bundle formation and turnover. THE PLANT CELL 2010; 22:2727-48. [PMID: 20807878 PMCID: PMC2947172 DOI: 10.1105/tpc.110.076240] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 07/29/2010] [Accepted: 08/17/2010] [Indexed: 05/20/2023]
Abstract
Actin filament bundles are higher-order cytoskeletal structures that are crucial for the maintenance of cellular architecture and cell expansion. They are generated from individual actin filaments by the actions of bundling proteins like fimbrins, LIMs, and villins. However, the molecular mechanisms of dynamic bundle formation and turnover are largely unknown. Villins belong to the villin/gelsolin/fragmin superfamily and comprise at least five isovariants in Arabidopsis thaliana. Different combinations of villin isovariants are coexpressed in various tissues and cells. It is not clear whether these isovariants function together and act redundantly or whether they have unique activities. VILLIN1 (VLN1) is a simple filament-bundling protein and is Ca(2+) insensitive. Based on phylogenetic analyses and conservation of Ca(2+) binding sites, we predict that VLN3 is a Ca(2+)-regulated villin capable of severing actin filaments and contributing to bundle turnover. The bundling activity of both isovariants was observed directly with time-lapse imaging and total internal reflection fluorescence (TIRF) microscopy in vitro, and the mechanism mimics the "catch and zipper" action observed in vivo. Using time-lapse TIRF microscopy, we observed and quantified the severing of individual actin filaments by VLN3 at physiological calcium concentrations. Moreover, VLN3 can sever actin filament bundles in the presence of VLN1 when calcium is elevated to micromolar levels. Collectively, these results demonstrate that two villin isovariants have overlapping and distinct activities.
Collapse
Affiliation(s)
- Parul Khurana
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Jessica L. Henty
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Shanjin Huang
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Andrew M. Staiger
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Laurent Blanchoin
- Institut de Recherches en Technologie et Sciences pour le Vivant, Commissariat à l'Energie Atomique/Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique/Université Joseph Fourier, Commissariat à l’Energie Atomique Grenoble, F38054 Grenoble, France
| | - Christopher J. Staiger
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
- The Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907
- Address correspondence to
| |
Collapse
|
50
|
Probing cytoplasmic organization and the actin cytoskeleton of plant cells with optical tweezers. Biochem Soc Trans 2010; 38:823-8. [DOI: 10.1042/bst0380823] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In interphase plant cells, the actin cytoskeleton is essential for intracellular transport and organization. To fully understand how the actin cytoskeleton functions as the structural basis for cytoplasmic organization, both molecular and physical aspects of the actin organization have to be considered. In the present review, we discuss literature that gives an insight into how cytoplasmic organization is achieved and in which actin-binding proteins have been identified that play a role in this process. We discuss how physical properties of the actin cytoskeleton in the cytoplasm of live plant cells, such as deformability and elasticity, can be probed by using optical tweezers. This technique allows non-invasive manipulation of cytoplasmic organization. Optical tweezers, integrated in a confocal microscope, can be used to manipulate cytoplasmic organization while studying actin dynamics. By combining this with mutant studies and drug applications, insight can be obtained about how the physical properties of the actin cytoskeleton, and thus the cytoplasmic organization, are influenced by different cellular processes.
Collapse
|