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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.
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Affiliation(s)
- Meng Shi
- Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
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Shaw SL, Ehrhardt DW. Smaller, faster, brighter: advances in optical imaging of living plant cells. ANNUAL REVIEW OF PLANT BIOLOGY 2013; 64:351-75. [PMID: 23506334 DOI: 10.1146/annurev-arplant-042110-103843] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The advent of fluorescent proteins and access to modern imaging technologies have dramatically accelerated the pace of discovery in plant cell biology. Remarkable new insights into such diverse areas as plant pathogenesis, cytoskeletal dynamics, sugar transport, cell wall synthesis, secretory control, and hormone signaling have come from careful examination of living cells using advanced optical probes. New technologies, both commercially available and on the horizon, promise a continued march toward more quantitative methods for imaging and for extending the optical exploration of biological structure and activity to molecular scales. In this review, we lay out fundamental issues in imaging plant specimens and look ahead to several technological innovations in molecular tools, instrumentation, imaging methods, and specimen handling that show promise for shaping the coming era of plant cell biology.
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Affiliation(s)
- Sidney L Shaw
- Department of Biology, Indiana University, Bloomington, IN 47405, USA.
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Abstract
Tip growth is employed throughout the plant kingdom. Our understanding of tip growth has benefited from modern tools in molecular genetics, which have enabled the functional characterization of proteins mediating tip growth. Here we first discuss the evolutionary role of tip growth in land plants and then describe the prominent model tip-growth systems, elaborating on some advantages and disadvantages of each. Next we review the organization of tip-growing cells, the role of the cytoskeleton, and recent developments concerning the physiological basis of tip growth. Finally, we review advances in the understanding of the extracellular signals that are known to guide tip-growing cells.
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Affiliation(s)
- Caleb M Rounds
- Department of Biological Sciences, Mount Holyoke College, South Hadley, MA 01075, USA
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Vidali L, Bezanilla M. Physcomitrella patens: a model for tip cell growth and differentiation. CURRENT OPINION IN PLANT BIOLOGY 2012; 15:625-31. [PMID: 23022392 DOI: 10.1016/j.pbi.2012.09.008] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Revised: 09/01/2012] [Accepted: 09/04/2012] [Indexed: 05/25/2023]
Abstract
The moss Physcomitrella patens has emerged as an excellent model system owing to its amenability to reverse genetics. The moss gametophyte has three filamentous tissues that grow by tip growth: chloronemata, caulonemata, and rhizoids. Because establishment of the moss plant relies on this form of growth, it is particularly suited for dissecting the molecular basis of tip growth. Recent studies demonstrate that a core set of actin cytoskeletal proteins is essential for tip growth. Additional actin cytoskeletal components are required for modulating growth to produce caulonemata and rhizoids. Differentiation into these cell types has previously been linked to auxin, light and nutrients. Recent studies have identified that core auxin signaling components as well as transcription factors that respond to auxin or nutrient levels are required for tip-growing cell differentiation. Future studies may establish a connection between the actin cytoskeleton and auxin or nutrient-induced cell differentiation.
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Affiliation(s)
- Luis Vidali
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA 01609, United States
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Li J, Henty-Ridilla JL, Huang S, Wang X, Blanchoin L, Staiger CJ. Capping protein modulates the dynamic behavior of actin filaments in response to phosphatidic acid in Arabidopsis. THE PLANT CELL 2012; 24:3742-54. [PMID: 22960908 PMCID: PMC3480299 DOI: 10.1105/tpc.112.103945] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Revised: 08/07/2012] [Accepted: 08/16/2012] [Indexed: 05/19/2023]
Abstract
Remodeling of actin filament arrays in response to biotic and abiotic stimuli is thought to require precise control over the generation and availability of filament ends. Heterodimeric capping protein (CP) is an abundant filament capper, and its activity is inhibited by membrane signaling phospholipids in vitro. How exactly CP modulates the properties of filament ends in cells and whether its activity is coordinated by phospholipids in vivo is not well understood. By observing directly the dynamic behavior of individual filament ends in the cortical array of living Arabidopsis thaliana epidermal cells, we dissected the contribution of CP to actin organization and dynamics in response to the signaling phospholipid, phosphatidic acid (PA). Here, we examined three cp knockdown mutants and found that reduced CP levels resulted in more dynamic activity at filament ends, and this significantly enhanced filament-filament annealing and filament elongation from free ends. The cp mutants also exhibited more dense actin filament arrays. Treatment of wild-type cells with exogenous PA phenocopied the actin-based defects in cp mutants, with an increase in the density of filament arrays and enhanced annealing frequency. These cytoskeletal responses to exogenous PA were completely abrogated in cp mutants. Our data provide compelling genetic evidence that the end-capping activity of CP is inhibited by membrane signaling lipids in eukaryotic cells. Specifically, CP acts as a PA biosensor and key transducer of fluxes in membrane signaling phospholipids into changes in actin cytoskeleton dynamics.
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Affiliation(s)
- Jiejie Li
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | | | - Shanjin Huang
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Xia Wang
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
| | - Laurent Blanchoin
- Institut de Recherches en Technologie et Sciences pour le Vivant, Laboratoire de Physiologie Cellulaire and Végétale, Commissariat á l’Energie Atomique/Centre National de la Recherche Scientifique/Institut National de la Recherche Agronomique/Université Joseph Fourier, F38054 Grenoble, France
| | - Christopher J. Staiger
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907-2064
- Bindley Bioscience Center, Purdue University, West Lafayette, Indiana 47907
- Address correspondence to
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van Gisbergen PAC, Li M, Wu SZ, Bezanilla M. Class II formin targeting to the cell cortex by binding PI(3,5)P(2) is essential for polarized growth. ACTA ACUST UNITED AC 2012; 198:235-50. [PMID: 22801781 PMCID: PMC3410418 DOI: 10.1083/jcb.201112085] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
PI(3,5)P2 is directly linked to generation and remodeling of the cortical actin array by formin during polarized cell growth in plants. Class II formins are key regulators of actin and are essential for polarized plant cell growth. Here, we show that the class II formin N-terminal phosphatase and tensin (PTEN) domain binds phosphoinositide-3,5-bisphosphate (PI(3,5)P2). Replacing the PTEN domain with polypeptides of known lipid-binding specificity, we show that PI(3,5)P2 binding was required for formin-mediated polarized growth. Via PTEN, formin also localized to the cell apex, phragmoplast, and to the cell cortex as dynamic cortical spots. We show that the cortical localization driven by binding to PI(3,5)P2 was required for function. Silencing the kinases that produce PI(3,5)P2 reduced cortical targeting of formin and inhibited polarized growth. We show a subset of cortical formin spots moved in actin-dependent linear trajectories. We observed that the linearly moving subpopulation of cortical formin generated new actin filaments de novo and along preexisting filaments, providing evidence for formin-mediated actin bundling in vivo. Taken together, our data directly link PI(3,5)P2 to generation and remodeling of the cortical actin array.
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Tóth R, Gerding-Reimers C, Deeks MJ, Menninger S, Gallegos RM, Tonaco IAN, Hübel K, Hussey PJ, Waldmann H, Coupland G. Prieurianin/endosidin 1 is an actin-stabilizing small molecule identified from a chemical genetic screen for circadian clock effectors in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 71:338-52. [PMID: 22409627 DOI: 10.1111/j.1365-313x.2012.04991.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Chemical modulators are powerful tools to investigate biological processes. To identify circadian clock effectors, we screened a natural product library in the model plant Arabidopsis thaliana. Two compounds, prieurianin (Pri) and prieurianin acetate, were identified as causing a shorter circadian period. Recently, Pri was independently identified as a vesicle trafficking inhibitor and re-named endosidin 1 (ES1). Here we show that Pri primarily affects actin filament flexibility in vivo, later resulting in reduced severing and filament depolymerization. This stabilization of the actin cytoskeleton subsequently causes changes in vesicle trafficking. Pri also affected microfilaments in mammalian cells, indicating that its target is highly conserved; however, it did not alter actin dynamics in vitro, suggesting that its activity requires the presence of actin-associated proteins. Furthermore, well-characterized actin inhibitors shortened the period length of the Arabidopsis clock in a similar way to Pri, supporting the idea that Pri affects rhythms by altering the actin network. We conclude that actin-associated processes influence the circadian system in a light-dependent manner, but their disruption does not abolish rhythmicity. In summary, we propose that the primary effect of Pri is to stabilize the actin cytoskeleton system, thereby affecting endosome trafficking. Pri appears to stabilize actin filaments by a different mechanism from previously described inhibitors, and will be a useful tool to study actin-related cellular processes.
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Affiliation(s)
- Réka Tóth
- Department of Plant Developmental Biology, Max Planck Institute for Plant Breeding Research, Cologne, Germany.
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Domozych DS. The quest for four-dimensional imaging in plant cell biology: it's just a matter of time. ANNALS OF BOTANY 2012; 110:461-74. [PMID: 22628381 PMCID: PMC3394652 DOI: 10.1093/aob/mcs107] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 04/04/2012] [Indexed: 05/22/2023]
Abstract
BACKGROUND Analysis of plant cell dynamics over time, or four-dimensional imaging (4-DI), represents a major goal of plant science. The ability to resolve structures in the third dimension within the cell or tissue during developmental events or in response to environmental or experimental stresses (i.e. 4-DI) is critical to our understanding of gene expression, post-expression modulations of macromolecules and sub-cellular system interactions. SCOPE Microscopy-based technologies have been profoundly integral to this type of investigation, and new and refined microscopy technologies now allow for the visualization of cell dynamics with unprecedented resolution, contrast and experimental versatility. However, certain realities of light and electron microscopy, choice of specimen and specimen preparation techniques limit the scope of readily attaining 4-DI. Today, the plant microscopist must use a combinatorial strategy whereby multiple microscopy-based investigations are used. Modern fluorescence, confocal laser scanning, transmission electron and scanning electron microscopy provide effective conduits for synthesizing data detailing live cell dynamics and highly resolved snapshots of specific cell structures that will ultimately lead to 4-DI. This review provides a synopsis of such technologies available.
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Affiliation(s)
- David S Domozych
- Department of Biology and Skidmore Microscopy Imaging Center, Skidmore College, Saratoga Springs, NY 12866, USA.
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