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Zhang T, Bai L, Guo Y. SCAB1 coordinates sequential Ca 2+ and ABA signals during osmotic stress induced stomatal closure in Arabidopsis. SCIENCE CHINA. LIFE SCIENCES 2024; 67:1-18. [PMID: 38153680 DOI: 10.1007/s11427-023-2480-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Accepted: 11/01/2023] [Indexed: 12/29/2023]
Abstract
Hyperosmotic stress caused by drought is a detrimental threat to plant growth and agricultural productivity due to limited water availability. Stomata are gateways of transpiration and gas exchange, the swift adjustment of stomatal aperture has a strong influence on plant drought resistance. Despite intensive investigations of stomatal closure during drought stress in past decades, little is known about how sequential signals are integrated during complete processes. Here, we discovered that the rapid Ca2+ signaling and subsequent abscisic acid (ABA) signaling contribute to the kinetics of both F-actin reorganizations and stomatal closure in Arabidopsis thaliana, while STOMATAL CLOSURE-RELATED ACTIN BINDING PROTEIN1 (SCAB1) is the molecular switch for this entire process. During the early stage of osmotic shock responses, swift elevated calcium signaling promotes SCAB1 phosphorylation through calcium sensors CALCIUM DEPENDENT PROTEIN KINASE3 (CPK3) and CPK6. The phosphorylation restrained the microfilament binding affinity of SCAB1, which bring about the F-actin disassembly and stomatal closure initiation. As the osmotic stress signal continued, both the kinase activity of CPK3 and the phosphorylation level of SCAB1 attenuated significantly. We further found that ABA signaling is indispensable for these attenuations, which presumably contributed to the actin filament reassembly process as well as completion of stomatal closure. Notably, the dynamic changes of SCAB1 phosphorylation status are crucial for the kinetics of stomatal closure. Taken together, our results support a model in which SCAB1 works as a molecular switch, and directs the microfilament rearrangement through integrating the sequentially generated Ca2+ and ABA signals during osmotic stress induced stomatal closure.
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Affiliation(s)
- Tianren Zhang
- State Key Laboratory of Plant Environmental Resilience, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Li Bai
- State Key Laboratory of Plant Environmental Resilience, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Yan Guo
- State Key Laboratory of Plant Environmental Resilience, College of Biological Sciences, China Agricultural University, Beijing, 100193, China.
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2
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Fu H, Yang X, Hao R, Han X, Song S, Guo Y, Yang Y. Phosphatidic acid inhibits SCAB1-mediated F-actin bundling in Arabidopsis. PLANT SIGNALING & BEHAVIOR 2023; 18:2092346. [PMID: 35757987 PMCID: PMC10730221 DOI: 10.1080/15592324.2022.2092346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 06/10/2022] [Accepted: 06/13/2022] [Indexed: 06/15/2023]
Abstract
Stomatal closure-associated actin-binding protein 1 (SCAB1) regulates stomatal closure by mediating actin filament reorganization in Arabidopsis thaliana. Our previous study showed that phosphatidylinositol 3-phosphate (PI3P) binds to SCAB1 and inhibits its oligomerization, thereby inhibiting its activity on F-actin in guard cells during stomatal closure. In this study, we show that another phospholipid, phosphatidic acid (PA), also binds to SCAB1 and inhibits its actin-bundling activity but not its actin-binding activity. F-actin bundling was promoted in vivo by treating Col-0 seedlings with n-butanol, a suppressor of PA production, but this effect was absent in the scab1 mutant. These results indicate that the signaling molecule PA is involved in the modulation of SCAB1 activity in F-actin reorganization.
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Affiliation(s)
- Haiqi Fu
- College of Biological Sciences, China Agricultural University, Beijing, Haidian, China
| | - Xinhao Yang
- College of Biological Sciences, China Agricultural University, Beijing, Haidian, China
| | - Rong Hao
- College of Biological Sciences, China Agricultural University, Beijing, Haidian, China
| | - Xiuli Han
- College of Biological Sciences, China Agricultural University, Beijing, Haidian, China
| | - Shu Song
- College of Biological Sciences, China Agricultural University, Beijing, Haidian, China
| | - Yan Guo
- College of Biological Sciences, China Agricultural University, Beijing, Haidian, China
| | - Yongqing Yang
- College of Biological Sciences, China Agricultural University, Beijing, Haidian, China
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3
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Shi Y, Liu X, Zhao S, Guo Y. The PYR-PP2C-CKL2 module regulates ABA-mediated actin reorganization during stomatal closure. THE NEW PHYTOLOGIST 2022; 233:2168-2184. [PMID: 34932819 DOI: 10.1111/nph.17933] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 11/29/2021] [Indexed: 05/20/2023]
Abstract
Limiting water loss by reducing transpiration helps plants survive when water is limited. Under drought stress, abscisic acid (ABA)-mediated gene expression and anion channel activation regulate stomatal closure and stress responses. ABA-induced actin reorganization also affects stomatal closure, but the underlying molecular mechanism remains unclear. In this study, we discovered that under nonstress conditions, the clade A PP2C phosphatases, such as ABI1 and ABI2, interact with CKL2 and inhibit its kinase activity in Arabidopsis. Under drought stress, CKL2 kinase activity was released through the formation of a complex containing ABA, PP2C and a PYR1/PYL/RCAR family (PYL) receptor. The activated CKL2 regulating actin reorganization is another important process to maintain stomatal closure besides ABA-activated SnRK2 signaling. Moreover, CKL2 phosphorylated PYR1-LIKE 1, ABI1 and ABI2 at amino acid residues conserved among PYLs and PP2Cs, and stabilized ABI1 protein. Our results reveal that ABA signaling regulates actin reorganization to maintain stomatal closure during drought stress, and the feedback regulation of PYL1, ABI1 and ABI2 by the CKL2 kinase might fine-tune ABA signaling and affect plant ABA responses.
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Affiliation(s)
- Yue Shi
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Xiangning Liu
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, 100193, China
| | - Shuangshuang 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
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4
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Yang Y, Zhao Y, Zheng W, Zhao Y, Zhao S, Wang Q, Bai L, Zhang T, Huang S, Song C, Yuan M, Guo Y. Phosphatidylinositol 3-phosphate regulates SCAB1-mediated F-actin reorganization during stomatal closure in Arabidopsis. THE PLANT CELL 2022; 34:477-494. [PMID: 34850207 PMCID: PMC8773959 DOI: 10.1093/plcell/koab264] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 10/22/2021] [Indexed: 05/20/2023]
Abstract
Stomatal movement is critical for plant responses to environmental changes and is regulated by the important signaling molecule phosphatidylinositol 3-phosphate (PI3P). However, the molecular mechanism underlying this process is not well understood. In this study, we show that PI3P binds to stomatal closure-related actin-binding protein1 (SCAB1), a plant-specific F-actin-binding and -bundling protein, and inhibits the oligomerization of SCAB1 to regulate its activity on F-actin in guard cells during stomatal closure in Arabidopsis thaliana. SCAB1 binds specifically to PI3P, but not to other phosphoinositides. Treatment with wortmannin, an inhibitor of phosphoinositide kinase that generates PI3P, leads to an increase of the intermolecular interaction and oligomerization of SCAB1, stabilization of F-actin, and retardation of F-actin reorganization during abscisic acid (ABA)-induced stomatal closure. When the binding activity of SCAB1 to PI3P is abolished, the mutated proteins do not rescue the stability and realignment of F-actin regulated by SCAB1 and the stomatal closure in the scab1 mutant. The expression of PI3P biosynthesis genes is consistently induced when the plants are exposed to drought and ABA treatments. Furthermore, the binding of PI3P to SCAB1 is also required for vacuolar remodeling during stomatal closure. Our results illustrate a PI3P-regulated pathway during ABA-induced stomatal closure, which involves the mediation of SCAB1 activity in F-actin reorganization.
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Affiliation(s)
| | | | | | - Yang Zhao
- Shanghai Center for Plant Stress Biology, CAS Center of Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 200032, China
| | - Shuangshuang Zhao
- Key Life Science College, Laboratory of Plant Stress, Shandong Normal University, Jinan 250014, China
| | - Qiannan Wang
- School of Life Sciences, Center for Plant Biology, Tsinghua University, Beijing 100084, China
| | - Li Bai
- College of Biological Sciences, State Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100193, China
| | - Tianren Zhang
- College of Biological Sciences, State Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100193, China
| | - Shanjin Huang
- School of Life Sciences, Center for Plant Biology, Tsinghua University, Beijing 100084, China
| | - Chunpeng Song
- Collaborative Innovation Center of Crop Stress Biology, Henan Province, Institute of Plant Stress Biology, Henan University, Kaifeng 475001, China
| | - Ming Yuan
- College of Biological Sciences, State Key Laboratory of Plant Physiology and Biochemistry, China Agricultural University, Beijing 100193, China
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5
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Li Y, Zhang X, Zhang Y, Ren H. Controlling the Gate: The Functions of the Cytoskeleton in Stomatal Movement. FRONTIERS IN PLANT SCIENCE 2022; 13:849729. [PMID: 35283892 PMCID: PMC8905143 DOI: 10.3389/fpls.2022.849729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 01/26/2022] [Indexed: 05/03/2023]
Abstract
Stomata are specialized epidermal structures composed of two guard cells and are involved in gas and water exchange between plants and the environment and pathogen entry into the plant interior. Stomatal movement is a response to many internal and external stimuli to increase adaptability to environmental change. The cytoskeleton, including actin filaments and microtubules, is highly dynamic in guard cells during stomatal movement, and the destruction of the cytoskeleton interferes with stomatal movement. In this review, we discuss recent progress on the organization and dynamics of actin filaments and microtubule network in guard cells, and we pay special attention to cytoskeletal-associated protein-mediated cytoskeletal rearrangements during stomatal movement. We also discuss the potential mechanisms of stomatal movement in relation to the cytoskeleton and attempt to provide a foundation for further research in this field.
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Affiliation(s)
- Yihao Li
- Center for Biological Science and Technology, Guangdong Zhuhai-Macao Joint Biotech Laboratory, Advanced Institute of Natural Science, Beijing Normal University, Zhuhai, China
| | - Xin Zhang
- Center for Biological Science and Technology, Guangdong Zhuhai-Macao Joint Biotech Laboratory, Advanced Institute of Natural Science, Beijing Normal University, Zhuhai, China
| | - Yi Zhang
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing, China
- *Correspondence: Yi Zhang,
| | - Haiyun Ren
- Center for Biological Science and Technology, Guangdong Zhuhai-Macao Joint Biotech Laboratory, Advanced Institute of Natural Science, Beijing Normal University, Zhuhai, China
- Key Laboratory of Cell Proliferation and Regulation Biology of Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing, China
- Haiyun Ren,
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6
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Wang X, Mao T. Understanding the functions and mechanisms of plant cytoskeleton in response to environmental signals. CURRENT OPINION IN PLANT BIOLOGY 2019; 52:86-96. [PMID: 31542697 DOI: 10.1016/j.pbi.2019.08.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 07/12/2019] [Accepted: 08/08/2019] [Indexed: 06/10/2023]
Abstract
Plants perceive multiple physiological and environmental signals in order to fine-tune their growth and development. The highly dynamic plant cytoskeleton, including actin and microtubule networks, can rapidly alter their organization, stability and dynamics in response to internal and external stimuli, which is considered vital for plant growth and adaptation to the environment. The cytoskeleton-associated proteins have been shown to be key regulatory molecules in mediating cytoskeleton reorganization in response to multiple environmental signals, such as light, salt, drought and biotic stimuli. Recent findings, including our studies, have expanded knowledge about the functions and underlying mechanisms of the plant cytoskeleton in environmental adaptation.
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Affiliation(s)
- Xiangfeng Wang
- State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Tonglin Mao
- State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
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7
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Shahriari S, Wei KJ, Ghildyal R. Respiratory Syncytial Virus Matrix (M) Protein Interacts with Actin In Vitro and in Cell Culture. Viruses 2018; 10:v10100535. [PMID: 30274351 PMCID: PMC6213044 DOI: 10.3390/v10100535] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Revised: 09/24/2018] [Accepted: 09/28/2018] [Indexed: 01/26/2023] Open
Abstract
The virus–host protein interactions that underlie respiratory syncytial virus (RSV) assembly are still not completely defined, despite almost 60 years of research. RSV buds from the apical surface of infected cells, once virion components have been transported to the budding sites. Association of RSV matrix (M) protein with the actin cytoskeleton may play a role in facilitating this transport. We have investigated the interaction of M with actin in vitro and cell culture. Purified wildtype RSV M protein was found to bind directly to polymerized actin in vitro. Vero cells were transfected to express full-length M (1–256) as a green fluorescent protein-(GFP) tagged protein, followed by treatment with the microfilament destabilizer, cytochalasin D. Destabilization of the microfilament network resulted in mislocalization of full-length M, from mostly cytoplasmic to diffused across both cytoplasm and nucleus, suggesting that M interacts with microfilaments in this system. Importantly, treatment of RSV-infected cells with cytochalasin D results in lower infectious virus titers, as well as mislocalization of M to the nucleus. Finally, using deletion mutants of M in a transfected cell system, we show that both the N- and C-terminus of the protein are required for the interaction. Together, our data suggest a possible role for M–actin interaction in transporting virion components in the infected cell.
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Affiliation(s)
- Shadi Shahriari
- Centre for Research in Therapeutic Solutions, Faculty of Science and Technology, University of Canberra, Canberra ACT 2617, Australia.
| | - Ke-Jun Wei
- Centre for Research in Therapeutic Solutions, Faculty of Science and Technology, University of Canberra, Canberra ACT 2617, Australia.
| | - Reena Ghildyal
- Centre for Research in Therapeutic Solutions, Faculty of Science and Technology, University of Canberra, Canberra ACT 2617, Australia.
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8
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Paez-Garcia A, Sparks JA, de Bang L, Blancaflor EB. Plant Actin Cytoskeleton: New Functions from Old Scaffold. PLANT CELL MONOGRAPHS 2018. [DOI: 10.1007/978-3-319-69944-8_6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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9
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Structural implications of Ca 2+-dependent actin-bundling function of human EFhd2/Swiprosin-1. Sci Rep 2016; 6:39095. [PMID: 27974828 PMCID: PMC5156911 DOI: 10.1038/srep39095] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 11/17/2016] [Indexed: 01/20/2023] Open
Abstract
EFhd2/Swiprosin-1 is a cytoskeletal Ca2+-binding protein implicated in Ca2+-dependent cell spreading and migration in epithelial cells. EFhd2 domain architecture includes an N-terminal disordered region, a PxxP motif, two EF-hands, a ligand mimic helix and a C-terminal coiled-coil domain. We reported previously that EFhd2 displays F-actin bundling activity in the presence of Ca2+ and this activity depends on the coiled-coil domain and direct interaction of the EFhd2 core region. However, the molecular mechanism for the regulation of F-actin binding and bundling by EFhd2 is unknown. Here, the Ca2+-bound crystal structure of the EFhd2 core region is presented and structures of mutants defective for Ca2+-binding are also described. These structures and biochemical analyses reveal that the F-actin bundling activity of EFhd2 depends on the structural rigidity of F-actin binding sites conferred by binding of the EF-hands to Ca2+. In the absence of Ca2+, the EFhd2 core region exhibits local conformational flexibility around the EF-hand domain and C-terminal linker, which retains F-actin binding activity but loses the ability to bundle F-actin. In addition, we establish that dimerisation of EFhd2 via the C-terminal coiled-coil domain, which is necessary for F-actin bundling, occurs through the parallel coiled-coil interaction.
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10
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Wood ER, Bledsoe R, Chai J, Daka P, Deng H, Ding Y, Harris-Gurley S, Kryn LH, Nartey E, Nichols J, Nolte RT, Prabhu N, Rise C, Sheahan T, Shotwell JB, Smith D, Tai V, Taylor JD, Tomberlin G, Wang L, Wisely B, You S, Xia B, Dickson H. The Role of Phosphodiesterase 12 (PDE12) as a Negative Regulator of the Innate Immune Response and the Discovery of Antiviral Inhibitors. J Biol Chem 2015; 290:19681-96. [PMID: 26055709 PMCID: PMC4528132 DOI: 10.1074/jbc.m115.653113] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Revised: 05/20/2015] [Indexed: 11/06/2022] Open
Abstract
2',5'-Oligoadenylate synthetase (OAS) enzymes and RNase-L constitute a major effector arm of interferon (IFN)-mediated antiviral defense. OAS produces a unique oligonucleotide second messenger, 2',5'-oligoadenylate (2-5A), that binds and activates RNase-L. This pathway is down-regulated by virus- and host-encoded enzymes that degrade 2-5A. Phosphodiesterase 12 (PDE12) was the first cellular 2-5A- degrading enzyme to be purified and described at a molecular level. Inhibition of PDE12 may up-regulate the OAS/RNase-L pathway in response to viral infection resulting in increased resistance to a variety of viral pathogens. We generated a PDE12-null cell line, HeLaΔPDE12, using transcription activator-like effector nuclease-mediated gene inactivation. This cell line has increased 2-5A levels in response to IFN and poly(I-C), a double-stranded RNA mimic compared with the parental cell line. Moreover, HeLaΔPDE12 cells were resistant to viral pathogens, including encephalomyocarditis virus, human rhinovirus, and respiratory syncytial virus. Based on these results, we used DNA-encoded chemical library screening to identify starting points for inhibitor lead optimization. Compounds derived from this effort raise 2-5A levels and exhibit antiviral activity comparable with the effects observed with PDE12 gene inactivation. The crystal structure of PDE12 complexed with an inhibitor was solved providing insights into the structure-activity relationships of inhibitor potency and selectivity.
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Affiliation(s)
| | | | - Jing Chai
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Philias Daka
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | - Hongfeng Deng
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Yun Ding
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | | | | | | | | | | | - Ninad Prabhu
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Cecil Rise
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Timothy Sheahan
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | - J Brad Shotwell
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | | | - Vince Tai
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | | | | | | | | | - Shihyun You
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
| | - Bing Xia
- ELT Boston, GlaxoSmithKline, Waltham, Massachusetts 02451
| | - Hamilton Dickson
- Antiviral Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina 27709 and
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11
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Wang C, Zheng Y, Zhao Y, Zhao Y, Li J, Guo Y. SCAB3 Is Required for Reorganization of Actin Filaments during Light Quality Changes. J Genet Genomics 2015; 42:161-8. [PMID: 25953354 DOI: 10.1016/j.jgg.2015.02.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Revised: 02/11/2015] [Accepted: 02/13/2015] [Indexed: 02/05/2023]
Abstract
The stomatal closure-related actin binding protein (SCAB) family is plant-specific, and its members all contain a novel actin binding domain. Here, we report that SCAB3, a homolog of SCAB1, binds, stabilizes and bundles actin filaments. The SCAB3 promoter contains a cis-element which could be bound by the FHY3/FAR1 transcription factors. Consistently, the expression of SCAB3 is induced when plants were transferred from white light to far red light (T-Far Red) conditions. The scab3 mutants show defects in the control of hypocotyl elongation under T-Far Red condition, which may result from an impaired reorganization of actin filaments. Together, our results suggest that SCAB3 plays an important role in plant growth under changes of light conditions possibly by regulating actin filament dynamics.
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Affiliation(s)
- Chongwu Wang
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yuan Zheng
- School of Life Science & Technology, Nanyang Normal University, Nanyang 473061, China
| | - Yang Zhao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Yi Zhao
- State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing 100193, China
| | - Jigang Li
- 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.
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12
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Abstract
Advances in microscopy techniques applied to living cells have dramatically transformed our view of the actin cytoskeleton as a framework for cellular processes. Conventional fluorescence imaging and static analyses are useful for quantifying cellular architecture and the network of filaments that support vesicle trafficking, organelle movement, and response to biotic stress. However, new imaging techniques have revealed remarkably dynamic features of individual actin filaments and the mechanisms that underpin their construction and turnover. In this review, we briefly summarize knowledge about actin and actin-binding proteins in plant systems. We focus on the quantitative properties of the turnover of individual actin filaments, highlight actin-binding proteins that participate in actin dynamics, and summarize the current genetic evidence that has been used to dissect specific aspects of the stochastic dynamics model. Finally, we describe some signaling pathways in which recent data implicate changes in actin filament dynamics and the associated cytoplasmic responses.
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Affiliation(s)
- Jiejie Li
- Department of Biological Sciences and
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13
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Hoffmann C, Moes D, Dieterle M, Neumann K, Moreau F, Tavares Furtado A, Dumas D, Steinmetz A, Thomas C. Live cell imaging reveals actin-cytoskeleton-induced self-association of the actin-bundling protein WLIM1. J Cell Sci 2014; 127:583-98. [PMID: 24284066 DOI: 10.1242/jcs.134536] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Crosslinking of actin filaments into bundles is essential for the assembly and stabilization of specific cytoskeletal structures. However, relatively little is known about the molecular mechanisms underlying actin bundle formation. The two LIM-domain-containing proteins define a novel and evolutionarily conserved family of actin-bundling proteins whose actin-binding and -crosslinking activities primarily rely on their LIM domains. Using TIRF microscopy, we describe real-time formation of actin bundles induced by tobacco NtWLIM1 in vitro. We show that NtWLIM1 binds to single filaments and subsequently promotes their interaction and zippering into tight bundles of mixed polarity. NtWLIM1-induced bundles grew by both elongation of internal filaments and addition of preformed fragments at their extremities. Importantly, these data are highly consistent with the modes of bundle formation and growth observed in transgenic Arabidopsis plants expressing a GFP-fused Arabidopsis AtWLIM1 protein. Using two complementary live cell imaging approaches, a close relationship between NtWLIM1 subcellular localization and self-association was established. Indeed, both BiFC and FLIM-FRET data revealed that, although unstable NtWLIM1 complexes can sporadically form in the cytosol, stable complexes concentrate along the actin cytoskeleton. Remarkably, disruption of the actin cytoskeleton significantly impaired self-association of NtWLIM1. In addition, biochemical analyses support the idea that F-actin facilitates the switch of purified recombinant NtWLIM1 from a monomeric to a di- or oligomeric state. On the basis of our data, we propose a model in which actin binding promotes the formation and stabilization of NtWLIM1 complexes, which in turn might drive the crosslinking of actin filaments.
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Affiliation(s)
- Céline Hoffmann
- Centre de Recherche Public-Santé, 84 Val Fleuri, L-1526 Luxembourg, Luxembourg
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14
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Kidane AI, Song Y, Nyarko A, Hall J, Hare M, Löhr F, Barbar E. Structural features of LC8-induced self-association of swallow. Biochemistry 2013; 52:6011-20. [PMID: 23914803 DOI: 10.1021/bi400642u] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Cell functions depend on the collective activity of protein networks within which a few proteins, called hubs, participate in a large number of interactions. Dynein light chain LC8, first discovered as a subunit of the motor protein dynein, is considered to have a role broader than that of dynein, and its participation in diverse systems fits the description of a hub. Among its partners is Swallow with which LC8 is essential for proper localization of bicoid mRNA at the anterior cortex of Drosophila oocytes. Why LC8 is essential in this process is not clear, but emerging evidence suggests that LC8 functions by promoting self-association and/or structural organization of its diverse binding partners. This work addresses the energetics and structural features of LC8-induced Swallow self-association distant from LC8 binding. Mutational design based on a hypothetical helical wheel, intermonomer nuclear Overhauser effects assigned to residues expected at interface positions, and circular dichroism spectral characteristics indicate that the LC8-promoted dimer of Swallow is a coiled coil. Secondary chemical shifts and (15)N backbone relaxation identify the boundaries and distinguishing structural features of the coiled coil. Thermodynamic analysis of Swallow polypeptides designed to decouple self-association from LC8 binding reveals that the higher binding affinity of the engineered bivalent Swallow is of purely entropic origin and that the linker separating the coiled coil from the LC8 binding site remains disordered. We speculate that the LC8-promoted coiled coil is critical for bicoid mRNA localization because it favors structural organization of Swallow, which except for the central LC8-promoted coiled coil is primarily disordered.
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Affiliation(s)
- Ariam I Kidane
- Department of Biochemistry and Biophysics, Oregon State University , Corvallis, Oregon 97331, United States
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15
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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.
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Affiliation(s)
- Clément Thomas
- Laboratory of Molecular and Cellular Oncology, Department of Oncology, Public Research Centre for Health (CRP-Santé)Luxembourg, Luxembourg
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