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Kong SG, Yamazaki Y, Shimada A, Kijima ST, Hirose K, Katoh K, Ahn J, Song HG, Han JW, Higa T, Takano A, Nakamura Y, Suetsugu N, Kohda D, Uyeda TQP, Wada M. CHLOROPLAST UNUSUAL POSITIONING 1 is a plant-specific actin polymerization factor regulating chloroplast movement. THE PLANT CELL 2024; 36:1159-1181. [PMID: 38134410 PMCID: PMC10980345 DOI: 10.1093/plcell/koad320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 11/09/2023] [Accepted: 12/18/2023] [Indexed: 12/24/2023]
Abstract
Plants have unique responses to fluctuating light conditions. One such response involves chloroplast photorelocation movement, which optimizes photosynthesis under weak light by the accumulation of chloroplasts along the periclinal side of the cell, which prevents photodamage under strong light by avoiding chloroplast positioning toward the anticlinal side of the cell. This light-responsive chloroplast movement relies on the reorganization of chloroplast actin (cp-actin) filaments. Previous studies have suggested that CHLOROPLAST UNUSUAL POSITIONING 1 (CHUP1) is essential for chloroplast photorelocation movement as a regulator of cp-actin filaments. In this study, we conducted comprehensive analyses to understand CHUP1 function. Functional, fluorescently tagged CHUP1 colocalized with and was coordinately reorganized with cp-actin filaments on the chloroplast outer envelope during chloroplast movement in Arabidopsis thaliana. CHUP1 distribution was reversibly regulated in a blue light- and phototropin-dependent manner. X-ray crystallography revealed that the CHUP1-C-terminal domain shares structural homology with the formin homology 2 (FH2) domain, despite lacking sequence similarity. Furthermore, the CHUP1-C-terminal domain promoted actin polymerization in the presence of profilin in vitro. Taken together, our findings indicate that CHUP1 is a plant-specific actin polymerization factor that has convergently evolved to assemble cp-actin filaments and enables chloroplast photorelocation movement.
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Affiliation(s)
- Sam-Geun Kong
- Department of Biological Sciences, College of Natural Sciences, Kongju National University, Chungnam 32588, Korea
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan
| | - Yosuke Yamazaki
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan
- Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Atsushi Shimada
- Division of Structural Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Saku T Kijima
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8562, Japan
| | - Keiko Hirose
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8562, Japan
| | - Kaoru Katoh
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8562, Japan
| | - Jeongsu Ahn
- Department of Biological Sciences, College of Natural Sciences, Kongju National University, Chungnam 32588, Korea
| | - Hyun-Geun Song
- Department of Biological Sciences, College of Natural Sciences, Kongju National University, Chungnam 32588, Korea
| | - Jae-Woo Han
- Department of Biological Sciences, College of Natural Sciences, Kongju National University, Chungnam 32588, Korea
| | - Takeshi Higa
- Institute for Protein Research, Osaka University, Osaka 565-0871, Japan
| | - Akira Takano
- Division of Structural Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Yuki Nakamura
- Division of Structural Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Noriyuki Suetsugu
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan
| | - Daisuke Kohda
- Division of Structural Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka 812-8582, Japan
| | - Taro Q P Uyeda
- Department of Physics, Faculty of Science and Engineering, Waseda University, Tokyo 169-8555, Japan
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8562, Japan
| | - Masamitsu Wada
- Department of Biology, Faculty of Sciences, Kyushu University, Fukuoka 812-8581, Japan
- Graduate School of Science, Tokyo Metropolitan University, Tokyo 192-0397, Japan
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2
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Sasaki T, Saito K, Inoue D, Serk H, Sugiyama Y, Pesquet E, Shimamoto Y, Oda Y. Confined-microtubule assembly shapes three-dimensional cell wall structures in xylem vessels. Nat Commun 2023; 14:6987. [PMID: 37957173 PMCID: PMC10643555 DOI: 10.1038/s41467-023-42487-w] [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: 02/17/2023] [Accepted: 10/12/2023] [Indexed: 11/15/2023] Open
Abstract
Properly patterned deposition of cell wall polymers is prerequisite for the morphogenesis of plant cells. A cortical microtubule array guides the two-dimensional pattern of cell wall deposition. Yet, the mechanism underlying the three-dimensional patterning of cell wall deposition is poorly understood. In metaxylem vessels, cell wall arches are formed over numerous pit membranes, forming highly organized three-dimensional cell wall structures. Here, we show that the microtubule-associated proteins, MAP70-5 and MAP70-1, regulate arch development. The map70-1 map70-5 plants formed oblique arches in an abnormal orientation in pits. Microtubules fit the aperture of developing arches in wild-type cells, whereas microtubules in map70-1 map70-5 cells extended over the boundaries of pit arches. MAP70 caused the bending and bundling of microtubules. These results suggest that MAP70 confines microtubules within the pit apertures by altering the physical properties of microtubules, thereby directing the growth of pit arches in the proper orientation. This study provides clues to understanding how plants develop three-dimensional structure of cell walls.
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Affiliation(s)
- Takema Sasaki
- Department of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan
| | - Kei Saito
- Department of Chromosome Science, National Institute of Genetics, Mishima, Shizuoka, Japan
- Department of Genetics, SOKENDAI University, Mishima, Shizuoka, Japan
| | - Daisuke Inoue
- Factuly of Design, Kyusyu University, Fukuoka, Japan
| | - Henrik Serk
- Umeå Plant Science Centre (UPSC), Department of Plant Physiology, Umeå University, Umeå, Sweden
| | - Yuki Sugiyama
- Department of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan
- Institute for Advanced Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan
| | - Edouard Pesquet
- Umeå Plant Science Centre (UPSC), Department of Plant Physiology, Umeå University, Umeå, Sweden
- Arrhenius laboratories, Department of Ecology, Environment and Plant Sciences (DEEP), Stockholm University, Stockholm, Sweden
| | - Yuta Shimamoto
- Department of Chromosome Science, National Institute of Genetics, Mishima, Shizuoka, Japan
- Department of Genetics, SOKENDAI University, Mishima, Shizuoka, Japan
| | - Yoshihisa Oda
- Department of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan.
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3
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Haarer BK, Pimm ML, de Jong EP, Amberg DC, Henty-Ridilla JL. Purification of human β- and γ-actin from budding yeast. J Cell Sci 2023; 136:jcs260540. [PMID: 37070275 PMCID: PMC10184827 DOI: 10.1242/jcs.260540] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 04/04/2023] [Indexed: 04/19/2023] Open
Abstract
Biochemical studies of human actin and its binding partners rely heavily on abundant and easily purified α-actin from skeletal muscle. Therefore, muscle actin has been used to evaluate and determine the activities of most actin regulatory proteins but there is an underlying concern that these proteins perform differently from actin present in non-muscle cells. To provide easily accessible and relatively abundant sources of human β- or γ-actin (i.e. cytoplasmic actins), we developed Saccharomyces cerevisiae strains that express each as their sole source of actin. Both β- or γ-actin purified in this system polymerize and interact with various binding partners, including profilin, mDia1 (formin), fascin and thymosin-β4 (Tβ4). Notably, Tβ4 and profilin bind to β- or γ-actin with higher affinity than to α-actin, emphasizing the value of testing actin ligands with specific actin isoforms. These reagents will make specific isoforms of actin more accessible for future studies on actin regulation.
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Affiliation(s)
- Brian K. Haarer
- Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, NY 13210, USA
| | - Morgan L. Pimm
- Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, NY 13210, USA
| | | | - David C. Amberg
- Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, NY 13210, USA
| | - Jessica L. Henty-Ridilla
- Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, NY 13210, USA
- Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
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4
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Numata T, Sugita K, Ahamed Rahman A, Rahman A. Actin isovariant ACT7 controls root meristem development in Arabidopsis through modulating auxin and ethylene responses. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:6255-6271. [PMID: 35749807 DOI: 10.1093/jxb/erac280] [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: 01/08/2022] [Accepted: 06/23/2022] [Indexed: 06/15/2023]
Abstract
The meristem is the most functionally dynamic part in a plant. The shaping of the meristem requires constant cell division and elongation, which are influenced by hormones and the cytoskeletal component, actin. Although the roles of hormones in modulating meristem development have been extensively studied, the role of actin in this process is still elusive. Using the single and double mutants of the vegetative class actin, we demonstrate that actin isovariant ACT7 plays an important role in root meristem development. In the absence of ACT7, but not ACT8 and ACT2, depolymerization of actin was observed. Consistently, the act7 mutant showed reduced cell division, cell elongation, and meristem length. Intracellular distribution and trafficking of auxin transport proteins in the actin mutants revealed that ACT7 specifically functions in the root meristem to facilitate the trafficking of auxin efflux carriers PIN1 and PIN2, and consequently the transport of auxin. Compared with act7, the act7act8 double mutant exhibited slightly enhanced phenotypic response and altered intracellular trafficking. The altered distribution of auxin in act7 and act7act8 affects the response of the roots to ethylene, but not to cytokinin. Collectively, our results suggest that ACT7-dependent auxin-ethylene response plays a key role in controlling Arabidopsis root meristem development.
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Affiliation(s)
- Takahiro Numata
- Department of Plant Bio Sciences, Faculty of Agriculture, Iwate University, Morioka, Japan
| | - Kenji Sugita
- Department of Plant Bio Sciences, Faculty of Agriculture, Iwate University, Morioka, Japan
| | - Arifa Ahamed Rahman
- The United Graduate School of Agricultural Sciences, Iwate University, Morioka, Japan
| | - Abidur Rahman
- Department of Plant Bio Sciences, Faculty of Agriculture, Iwate University, Morioka, Japan
- The United Graduate School of Agricultural Sciences, Iwate University, Morioka, Japan
- Department of Plant Sciences, College of Agriculture and Bioresources, University of Saskatchewan, Saskatoon, SK, Canada
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5
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Vahokoski J, Calder LJ, Lopez AJ, Molloy JE, Kursula I, Rosenthal PB. High-resolution structures of malaria parasite actomyosin and actin filaments. PLoS Pathog 2022; 18:e1010408. [PMID: 35377914 PMCID: PMC9037914 DOI: 10.1371/journal.ppat.1010408] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 04/25/2022] [Accepted: 03/01/2022] [Indexed: 12/20/2022] Open
Abstract
Malaria is responsible for half a million deaths annually and poses a huge economic burden on the developing world. The mosquito-borne parasites (Plasmodium spp.) that cause the disease depend upon an unconventional actomyosin motor for both gliding motility and host cell invasion. The motor system, often referred to as the glideosome complex, remains to be understood in molecular terms and is an attractive target for new drugs that might block the infection pathway. Here, we present the high-resolution structure of the actomyosin motor complex from Plasmodium falciparum. The complex includes the malaria parasite actin filament (PfAct1) complexed with the class XIV myosin motor (PfMyoA) and its two associated light-chains. The high-resolution core structure reveals the PfAct1:PfMyoA interface in atomic detail, while at lower-resolution, we visualize the PfMyoA light-chain binding region, including the essential light chain (PfELC) and the myosin tail interacting protein (PfMTIP). Finally, we report a bare PfAct1 filament structure at improved resolution.
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Affiliation(s)
- Juha Vahokoski
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Lesley J. Calder
- Structural Biology of Cells and Viruses Laboratory, Francis Crick Institute, London, United Kingdom
| | - Andrea J. Lopez
- Department of Biomedicine, University of Bergen, Bergen, Norway
| | - Justin E. Molloy
- Structural Biology of Cells and Viruses Laboratory, Francis Crick Institute, London, United Kingdom
| | - Inari Kursula
- Department of Biomedicine, University of Bergen, Bergen, Norway
- Biocenter Oulu and Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Peter B. Rosenthal
- Structural Biology of Cells and Viruses Laboratory, Francis Crick Institute, London, United Kingdom
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Boiero Sanders M, Toret CP, Guillotin A, Antkowiak A, Vannier T, Robinson RC, Michelot A. Specialization of actin isoforms derived from the loss of key interactions with regulatory factors. EMBO J 2022; 41:e107982. [PMID: 35178724 PMCID: PMC8886540 DOI: 10.15252/embj.2021107982] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 01/19/2022] [Accepted: 01/21/2022] [Indexed: 11/09/2022] Open
Abstract
A paradox of eukaryotic cells is that while some species assemble a complex actin cytoskeleton from a single ortholog, other species utilize a greater diversity of actin isoforms. The physiological consequences of using different actin isoforms, and the molecular mechanisms by which highly conserved actin isoforms are segregated into distinct networks, are poorly known. Here, we sought to understand how a simple biological system, composed of a unique actin and a limited set of actin‐binding proteins, reacts to a switch to heterologous actin expression. Using yeast as a model system and biomimetic assays, we show that such perturbation causes drastic reorganization of the actin cytoskeleton. Our results indicate that defective interaction of a heterologous actin for important regulators of actin assembly limits certain actin assembly pathways while reinforcing others. Expression of two heterologous actin variants, each specialized in assembling a different network, rescues cytoskeletal organization and confers resistance to external perturbation. Hence, while species using a unique actin have homeostatic actin networks, actin assembly pathways in species using several actin isoforms may act more independently.
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Affiliation(s)
| | - Christopher P Toret
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
| | - Audrey Guillotin
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
| | - Adrien Antkowiak
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
| | - Thomas Vannier
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
| | - Robert C Robinson
- Research Institute for Interdisciplinary Science (RIIS), Okayama University, Okayama, Japan.,School of Biomolecular Science and Engineering (BSE), Vidyasirimedhi Institute of Science and Technology (VISTEC), Rayong, Thailand
| | - Alphée Michelot
- CNRS, IBDM, Turing Centre for Living Systems, Aix Marseille Univ, Marseille, France
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7
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Fujita S. CASPARIAN STRIP INTEGRITY FACTOR (CIF) family peptides - regulator of plant extracellular barriers. Peptides 2021; 143:170599. [PMID: 34174383 DOI: 10.1016/j.peptides.2021.170599] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 05/24/2021] [Accepted: 06/18/2021] [Indexed: 01/17/2023]
Abstract
In multicellular organisms, water and most of the small molecules, such as nutrients, toxic substances, and signaling compounds, move freely through extracellular spaces, depending on their biochemical nature. To restrict the simple diffusion of small molecules, multicellular organisms have evolved extracellular barriers across specific tissue layers, such as tight junctions in the animal epithelium. Similar extracellular barriers are also generated in plants through the accumulation of hydrophobic chemicals, such as lignin or cutin, although the detailed molecular mechanisms underlying this process remain elusive. Here, I summarize recent advances in extracellular barrier formation in plants by focusing mainly on CASPARIAN STRIP INTEGRITY FACTOR (CIF) family peptides, which trigger the spatially precise deposition of designated cell wall components, enabling plants to establish transcellular barrier networks correctly. The genome of Arabidopsis thaliana, a model plant species, harbors five CIF genes, which encode propeptides which are processed into small secreted peptides of 21-24 amino acids. Sulfation of tyrosine residues in CIF peptides ensures their full bioactivity and high-affinity binding to their receptors SCHENGEN3/GASSHO1 (SGN3/GSO1) and GSO2 in vitro. Additionally, in vivo analysis shows that physical restriction of CIF peptide diffusion and the subcellular localization of a signaling module and expression patterns of a peptide processing enzyme specify the location of signal activation. Thus, the CIF peptide family provides fascinating models for understanding mature peptide biogenesis and spatially limited signal activation with small diffusive molecules.
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Affiliation(s)
- Satoshi Fujita
- National Institute of Genetics, 1111 Yata, Mishima, Shizuoka, 411-8540, Japan.
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8
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Parveen S, Rahman A. Actin Isovariant ACT7 Modulates Root Thermomorphogenesis by Altering Intracellular Auxin Homeostasis. Int J Mol Sci 2021; 22:7749. [PMID: 34299366 PMCID: PMC8306570 DOI: 10.3390/ijms22147749] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2021] [Revised: 07/11/2021] [Accepted: 07/18/2021] [Indexed: 12/16/2022] Open
Abstract
High temperature stress is one of the most threatening abiotic stresses for plants limiting the crop productivity world-wide. Altered developmental responses of plants to moderate-high temperature has been shown to be linked to the intracellular auxin homeostasis regulated by both auxin biosynthesis and transport. Trafficking of the auxin carrier proteins plays a major role in maintaining the cellular auxin homeostasis. The intracellular trafficking largely relies on the cytoskeletal component, actin, which provides track for vesicle movement. Different classes of actin and the isovariants function in regulating various stages of plant development. Although high temperature alters the intracellular trafficking, the role of actin in this process remains obscure. Using isovariant specific vegetative class actin mutants, here we demonstrate that ACTIN 7 (ACT7) isovariant plays an important role in regulating the moderate-high temperature response in Arabidopsis root. Loss of ACT7, but not ACT8 resulted in increased inhibition of root elongation under prolonged moderate-high temperature. Consistently, kinematic analysis revealed a drastic reduction in cell production rate and cell elongation in act7-4 mutant under high temperature. Quantification of actin dynamicity reveals that prolonged moderate-high temperature modulates bundling along with orientation and parallelness of filamentous actin in act7-4 mutant. The hypersensitive response of act7-4 mutant was found to be linked to the altered intracellular auxin distribution, resulted from the reduced abundance of PIN-FORMED PIN1 and PIN2 efflux carriers. Collectively, these results suggest that vegetative class actin isovariant, ACT7 modulates the long-term moderate-high temperature response in Arabidopsis root.
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Affiliation(s)
- Sumaya Parveen
- United Graduate School of Agricultural Sciences, Iwate University, Morioka 020-8550, Japan;
| | - Abidur Rahman
- United Graduate School of Agricultural Sciences, Iwate University, Morioka 020-8550, Japan;
- Department of Plant Bio Sciences, Faculty of Agriculture, Iwate University, Morioka 020-8550, Japan
- Agri-Innovation Center, Faculty of Agriculture, Iwate University, Morioka 020-8550, Japan
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9
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Michonneau P, Fleurat-Lessard P, Cantereau A, Crépin A, Roblin G, Berjeaud JM. Implication of actin in the uptake of sucrose and valine in the tap root and leaf of sugar beet. PHYSIOLOGIA PLANTARUM 2021; 172:218-232. [PMID: 33421161 DOI: 10.1111/ppl.13322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 12/18/2020] [Indexed: 06/12/2023]
Abstract
Actin microfilaments (F-actin) are major components of the cytoskeleton essential for many cellular dynamic processes (vesicle trafficking, cytoplasmic streaming, organelle movements). The aim of this study was to examine whether cortical actin microfilaments might be implicated in the regulation of nutrient uptake in root and leaf cells of Beta vulgaris. Using antibodies raised against actin and the AtSUC1 sucrose transporter, immunochemical assays demonstrated that the expression of actin and a sucrose transporter showed different characteristics, when detected on plasma membrane vesicles (PMVs) purified from roots and from leaves. The in situ immunolabeling of actin and AtSUC1 sites in PMVs and tissues showed their close proximity to the plasma membrane. Using co-labeling in protoplasts, actin and sucrose transporters were localized along the internal border and in the outermost part of the plasma membrane, respectively. This respective membrane co-localization was confirmed on PMVs and in tissues using transmission electronic microscopy. The possible functional role of actin in sucrose uptake (and valine uptake, comparatively) by PMVs and tissues from roots and leaves was examined using the pharmacological inhibitors, cytochalasin B (CB), cytochalasin D (CD), and phalloidin (PH). CB and CD inhibited the sucrose and valine uptake by root tissues in a concentration-dependent manner above 1 μM, whereas PH had no such effect. Comparatively, the toxins inhibited the sucrose and valine uptake in leaf discs to a lesser extent. The inhibition was not due to a hindering of the proton pumping and H+ -ATPase catalytic activity determined in PMVs incubated in presence of these toxins.
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Affiliation(s)
- Philippe Michonneau
- Pôle Agronomie Innovation Services, SCARA, Villette-sur-Aube, France
- Laboratoire EBI (Ecologie et Biologie des Interactions, Université de Poitiers, Poitiers, France
| | | | - Anne Cantereau
- Plateforme ImageUP, Signalisation & Transports Ioniques Membranaires CNRS 6187, Poitiers, France
| | - Alexandre Crépin
- Laboratoire EBI (Ecologie et Biologie des Interactions, Université de Poitiers, Poitiers, France
| | - Gabriel Roblin
- Laboratoire EBI (Ecologie et Biologie des Interactions, Université de Poitiers, Poitiers, France
| | - Jean-Marc Berjeaud
- Laboratoire EBI (Ecologie et Biologie des Interactions, Université de Poitiers, Poitiers, France
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Boiero Sanders M, Antkowiak A, Michelot A. Diversity from similarity: cellular strategies for assigning particular identities to actin filaments and networks. Open Biol 2020; 10:200157. [PMID: 32873155 PMCID: PMC7536088 DOI: 10.1098/rsob.200157] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The actin cytoskeleton has the particularity of being assembled into many functionally distinct filamentous networks from a common reservoir of monomeric actin. Each of these networks has its own geometrical, dynamical and mechanical properties, because they are capable of recruiting specific families of actin-binding proteins (ABPs), while excluding the others. This review discusses our current understanding of the underlying molecular mechanisms that cells have developed over the course of evolution to segregate ABPs to appropriate actin networks. Segregation of ABPs requires the ability to distinguish actin networks as different substrates for ABPs, which is regulated in three different ways: (1) by the geometrical organization of actin filaments within networks, which promotes or inhibits the accumulation of ABPs; (2) by the identity of the networks' filaments, which results from the decoration of actin filaments with additional proteins such as tropomyosin, from the use of different actin isoforms or from covalent modifications of actin; (3) by the existence of collaborative or competitive binding to actin filaments between two or multiple ABPs. This review highlights that all these effects need to be taken into account to understand the proper localization of ABPs in cells, and discusses what remains to be understood in this field of research.
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Affiliation(s)
- Micaela Boiero Sanders
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Adrien Antkowiak
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
| | - Alphée Michelot
- Aix Marseille University, CNRS, IBDM, Turing Centre for Living Systems, Marseille, France
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11
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Sheahan MB, Collings DA, Rose RJ, McCurdy DW. ACTIN7 Is Required for Perinuclear Clustering of Chloroplasts during Arabidopsis Protoplast Culture. PLANTS 2020; 9:plants9020225. [PMID: 32050601 PMCID: PMC7076399 DOI: 10.3390/plants9020225] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Revised: 01/28/2020] [Accepted: 02/07/2020] [Indexed: 11/16/2022]
Abstract
In Arabidopsis, the actin gene family comprises eight expressed and two non-expressed ACTIN (ACT) genes. Of the eight expressed isoforms, ACT2, ACT7, and ACT8 are differentially expressed in vegetative tissues and may perform specific roles in development. Using tobacco mesophyll protoplasts, we previously demonstrated that actin-dependent clustering of chloroplasts around the nucleus prior to cell division ensures unbiased chloroplast inheritance. Here, we report that actin-dependent chloroplast clustering in Arabidopsis mesophyll protoplasts is defective in act7 mutants, but not act2-1 or act8-2. ACT7 expression was upregulated during protoplast culture whereas ACT2 and ACT8 expression did not substantially change. In act2-1, ACT7 expression increased in response to loss of ACT2, whereas in act7-1, neither ACT2 nor ACT8 expression changed appreciably in response to the absence of ACT7. Semi-quantitative immunoblotting revealed increased actin concentrations during culture, although total actin in act7-1 was only two-thirds that of wild-type or act2-1 after 96 h culture. Over-expression of ACT2 and ACT8 under control of ACT7 regulatory sequences restored normal levels of chloroplast clustering. These results are consistent with a requirement for ACT7 in actin-dependent chloroplast clustering due to reduced levels of actin protein and gene induction in act7 mutants, rather than strong functional specialization of the ACT7 isoform.
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12
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Hatano T, Sivashanmugam L, Suchenko A, Hussain H, Balasubramanian MK. Pick-ya actin - a method to purify actin isoforms with bespoke key post-translational modifications. J Cell Sci 2020; 133:jcs241406. [PMID: 31964701 PMCID: PMC7615240 DOI: 10.1242/jcs.241406] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Accepted: 12/20/2019] [Indexed: 12/21/2022] Open
Abstract
Actin is one of the most abundant eukaryotic cytoskeletal polymer-forming proteins, which, in the filamentous form, regulates a number of physiological processes, ranging from cell division and migration to development and tissue function. Actins have different post-translational modifications (PTMs) in different organisms, including methionine, alanine, aspartate and glutamate N-acetylation, N-arginylation and the methylation of the histidine at residue 73 (His-73), with different organisms displaying a distinct signature of PTMs. Currently, methods are not available to produce actin isoforms with an organism-specific PTM profile. Here, we report the Pick-ya actin method, a method to express actin isoforms from any eukaryote with its own key characteristic PTM pattern. We achieve this using a synthetic biology strategy in a yeast strain that expresses, one, actin isoforms with the desired N-end via ubiquitin fusion and, two, mammalian enzymes that promote acetylation and methylation. Pick-ya actin should greatly facilitate biochemical, structural and physiological studies of the actin cytoskeleton and its PTMs.
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Affiliation(s)
- Tomoyuki Hatano
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Lavanya Sivashanmugam
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Andrejus Suchenko
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Hamdi Hussain
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Mohan K Balasubramanian
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
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13
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F-actin homeostasis through transcriptional regulation and proteasome-mediated proteolysis. Proc Natl Acad Sci U S A 2018; 115:E6487-E6496. [PMID: 29941587 DOI: 10.1073/pnas.1721935115] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Many organisms possess multiple and often divergent actins whose regulation and roles are not understood in detail. For example, Chlamydomonas reinhardtii has both a conventional actin (IDA5) and a highly divergent one (NAP1); only IDA5 is expressed in normal proliferating cells. We showed previously that the drug latrunculin B (LatB) causes loss of filamentous (F-) IDA5 and strong up-regulation of NAP1, which then provides essential actin function(s) by forming LatB-resistant F-NAP1. RNA-sequencing analyses now show that this up-regulation of NAP1 reflects a broad transcriptional response, much of which depends on three proteins (LAT1, LAT2, and LAT3) identified previously as essential for NAP1 transcription. Many of the LAT-regulated genes contain a putative cis-acting regulatory site, the "LRE motif." The LatB transcriptional program appears to be activated by loss of F-IDA5 and deactivated by formation of F-NAP1, thus forming an F-actin-dependent negative-feedback loop. Multiple genes encoding proteins of the ubiquitin-proteasome system are among those induced by LatB, resulting in rapid degradation of IDA5 (but not NAP1). Our results suggest that IDA5 degradation is functionally important because nonpolymerizable LatB-bound IDA5 interferes with the formation of F-NAP1. The genes for the actin-interacting proteins cofilin and profilin are also induced. Cofilin induction may further the clearance of IDA5 by promoting the scission of F-IDA5, whereas profilin appears to function in protecting monomeric IDA5 from degradation. This multifaceted regulatory system allows rapid and quantitative turnover of F-actin in response to cytoskeletal perturbations and probably also maintains F-actin homeostasis under normal growth conditions.
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14
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Hatano T, Alioto S, Roscioli E, Palani S, Clarke ST, Kamnev A, Hernandez-Fernaud JR, Sivashanmugam L, Chapa-Y-Lazo B, Jones AME, Robinson RC, Sampath K, Mishima M, McAinsh AD, Goode BL, Balasubramanian MK. Rapid production of pure recombinant actin isoforms in Pichia pastoris. J Cell Sci 2018. [PMID: 29535210 PMCID: PMC5976186 DOI: 10.1242/jcs.213827] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Actins are major eukaryotic cytoskeletal proteins, and they are involved in many important cell functions, including cell division, cell polarity, wound healing and muscle contraction. Despite obvious drawbacks, muscle actin, which is easily purified, is used extensively for biochemical studies of the non-muscle actin cytoskeleton. Here, we report a rapid and cost-effective method to purify heterologous actins expressed in the yeast Pichia pastoris. Actin is expressed as a fusion with the actin-binding protein thymosin β4 and purified by means of an affinity tag introduced in the fusion. Following cleavage of thymosin β4 and the affinity tag, highly purified functional full-length actin is liberated. We purify actins from Saccharomycescerevisiae and Schizosaccharomycespombe, and the β- and γ-isoforms of human actin. We also report a modification of the method that facilitates expression and purification of arginylated actin, a form of actin thought to regulate dendritic actin networks in mammalian cells. The methods we describe can be performed in all laboratories equipped for molecular biology, and should greatly facilitate biochemical and cell biological studies of the actin cytoskeleton. Summary:Here, we describe a method to purify recombinant actin to homogeneity by expression in Pichia pastoris. The purified actin is polymerisation competent and should facilitate biochemical and cell biological studies of the actin cytoskeleton.
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Affiliation(s)
- Tomoyuki Hatano
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Salvatore Alioto
- Department of Biology, Brandeis University, Waltham, MA 02454, USA
| | - Emanuele Roscioli
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Saravanan Palani
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Scott T Clarke
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Anton Kamnev
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | | | - Lavanya Sivashanmugam
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Bernardo Chapa-Y-Lazo
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | | | - Robert C Robinson
- Institute of Molecular and Cell Biology, A*STAR (Agency for Science, Technology, and Research), Singapore 138673, Singapore.,Department of Biochemistry, National University of Singapore, Singapore 117597, Singapore.,Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530, Japan
| | - Karuna Sampath
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Masanori Mishima
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Andrew D McAinsh
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
| | - Bruce L Goode
- Department of Biology, Brandeis University, Waltham, MA 02454, USA
| | - Mohan K Balasubramanian
- Centre for Mechanochemical Cell Biology and Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry CV4 7AL, UK
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15
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Dohn TE, Cripps RM. Absence of the Drosophila jump muscle actin Act79B is compensated by up-regulation of Act88F. Dev Dyn 2018; 247:642-649. [PMID: 29318731 PMCID: PMC6118211 DOI: 10.1002/dvdy.24616] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 01/04/2018] [Accepted: 01/08/2018] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Actins are structural components of the cytoskeleton and muscle, and numerous actin isoforms are found in most organisms. However, many actin isoforms are expressed in distinct patterns allowing each actin to have a specialized function. Numerous studies have demonstrated that actin isoforms both can and cannot compensate for each other under specific circumstances. This allows for an ambiguity of whether isoforms are functionally distinct. RESULTS In this study, we analyzed mutants of Drosophila Act79B, the predominant actin expressed in the adult jump muscle. Functional and structural analysis of the Act79B mutants found the flies to have normal jumping ability and sarcomere structure. Analysis of actin gene expression determined that expression of Act88F, an actin gene normally expressed in the flight muscles, was significantly up-regulated in the jump muscles of mutants. This indicated that loss of Act79B caused expansion of Act88F expression. When we created double mutants of Act79B and Act88F, this abolished the jump ability of the flies and resulted in severe defects in myofibril formation. CONCLUSIONS These results indicate that Act88F can functionally substitute for Act79B in the jump muscle, and that the functional compensation in actin expression in the jump muscles only occurs through Act88F. Developmental Dynamics 247:642-649, 2018. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Tracy E. Dohn
- Department of Biology, University of New Mexico, Albuquerque, New Mexico
| | - Richard M. Cripps
- Department of Biology, University of New Mexico, Albuquerque, New Mexico
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16
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Arabidopsis vegetative actin isoforms, AtACT2 and AtACT7, generate distinct filament arrays in living plant cells. Sci Rep 2018. [PMID: 29531328 PMCID: PMC5847576 DOI: 10.1038/s41598-018-22707-w] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Flowering plants express multiple actin isoforms. Previous studies suggest that individual actin isoforms have specific functions; however, the subcellular localization of actin isoforms in plant cells remains obscure. Here, we transiently expressed and observed major Arabidopsis vegetative actin isoforms, AtACT2 and AtACT7, as fluorescent-fusion proteins. By optimizing the linker sequence between fluorescent protein and actin, we succeeded in observing filaments that contained these expressed actin isoforms fused with green fluorescent protein (GFP) in Arabidopsis protoplasts. Different colored fluorescent proteins fused with AtACT2 and AtACT7 and co-expressed in Nicotiana benthamiana mesophyll cells co-polymerized in a segregated manner along filaments. In epidermal cells, surprisingly, AtACT2 and AtACT7 tended to polymerize into different types of filaments. AtACT2 was incorporated into thinner filaments, whereas AtACT7 was incorporated into thick bundles. We conclude that different actin isoforms are capable of constructing unique filament arrays, depending on the cell type or tissue. Interestingly, staining patterns induced by two indirect actin filament probes, Lifeact and mTalin1, were different between filaments containing AtACT2 and those containing AtACT7. We suggest that filaments containing different actin isoforms bind specific actin-binding proteins in vivo, since the two probes comprise actin-binding domains from different actin-binding proteins.
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17
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Duan Z, Tominaga M. Actin-myosin XI: an intracellular control network in plants. Biochem Biophys Res Commun 2018; 506:403-408. [PMID: 29307817 DOI: 10.1016/j.bbrc.2017.12.169] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Accepted: 12/31/2017] [Indexed: 11/29/2022]
Abstract
Actin is one of the three major cytoskeletal components in eukaryotic cells. Myosin XI is an actin-based motor protein in plant cells. Organelles are attached to myosin XI and translocated along the actin filaments. This dynamic actin-myosin XI system plays a major role in subcellular organelle transport and cytoplasmic streaming. Previous studies have revealed that myosin-driven transport and the actin cytoskeleton play essential roles in plant cell growth. Recent data have indicated that the actin-myosin XI cytoskeleton is essential for not only cell growth but also reproductive processes and responses to the environment. In this review, we have summarized previous reports regarding the role of the actin-myosin XI cytoskeleton in cytoplasmic streaming and plant development and recent advances in the understanding of the functions of actin-myosin XI cytoskeleton in Arabidopsis thaliana.
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Affiliation(s)
- Zhongrui Duan
- Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan
| | - Motoki Tominaga
- Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan; Major in Integrative Bioscience and Biomedical Engineering, Graduate School of Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo, 162-8480, Japan.
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18
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Rula S, Suwa T, Kijima ST, Haraguchi T, Wakatsuki S, Sato N, Duan Z, Tominaga M, Uyeda TQP, Ito K. Measurement of enzymatic and motile activities of Arabidopsis myosins by using Arabidopsis actins. Biochem Biophys Res Commun 2017; 495:2145-2151. [PMID: 29248727 DOI: 10.1016/j.bbrc.2017.12.071] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 12/13/2017] [Indexed: 11/16/2022]
Abstract
There are two classes of myosin, XI and VIII, in higher plants. Myosin XI moves actin filaments at high speed and its enzyme activity is also very high. In contrast, myosin VIII moves actin filaments very slowly with very low enzyme activity. Because most of these enzymatic and motile activities were measured using animal skeletal muscle α-actin, but not plant actin, they would not accurately reflect the actual activities in plant cells. We thus measured enzymatic and motile activities of the motor domains of two Arabidopsis myosin XI isoforms (MYA2, XI-B), and one Arabidopsis myosin VIII isoform (ATM1), by using three Arabidopsis actin isoforms (ACT1, ACT2, and ACT7). The measured activities were different from those measured by using muscle actin. Moreover, Arabidopsis myosins showed different enzymatic and motile activities when using different Arabidopsis actin isoforms. Our results suggest that plant actin should be used for measuring enzymatic and motile activities of plant myosins and that different actin isoforms in plant cells might function as different tracks along which affinities and velocities of each myosin isoform are modulated.
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Affiliation(s)
- Sa Rula
- Department of Biology, Graduate School of Science, Chiba University, Inage-ku, Chiba 263-8522, Japan
| | - Takahiro Suwa
- Department of Biology, Graduate School of Science, Chiba University, Inage-ku, Chiba 263-8522, Japan
| | - Saku T Kijima
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8565, Japan; Graduate School of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan
| | - Takeshi Haraguchi
- Department of Biology, Graduate School of Science, Chiba University, Inage-ku, Chiba 263-8522, Japan
| | - Shinryu Wakatsuki
- Department of Biology, Graduate School of Science, Chiba University, Inage-ku, Chiba 263-8522, Japan
| | - Naruki Sato
- Department of Biology, Graduate School of Science, Chiba University, Inage-ku, Chiba 263-8522, Japan
| | - Zhongrui Duan
- Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Motoki Tominaga
- Faculty of Education and Integrated Arts and Sciences, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan; Department of Integrative Bioscience and Biomedical Engineering, Graduate School of Advanced Science and Engineering, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Taro Q P Uyeda
- Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8565, Japan; Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Kohji Ito
- Department of Biology, Graduate School of Science, Chiba University, Inage-ku, Chiba 263-8522, Japan.
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Mattei B, Spinelli F, Pontiggia D, De Lorenzo G. Comprehensive Analysis of the Membrane Phosphoproteome Regulated by Oligogalacturonides in Arabidopsis thaliana. FRONTIERS IN PLANT SCIENCE 2016; 7:1107. [PMID: 27532006 PMCID: PMC4969306 DOI: 10.3389/fpls.2016.01107] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 07/12/2016] [Indexed: 05/03/2023]
Abstract
Early changes in the Arabidopsis thaliana membrane phosphoproteome in response to oligogalacturonides (OGs), a class of plant damage-associated molecular patterns (DAMPs), were analyzed by two complementary proteomic approaches. Differentially phosphorylated sites were determined through phosphopeptide enrichment followed by LC-MS/MS using label-free quantification; differentially phosphorylated proteins were identified by 2D-DIGE combined with phospho-specific fluorescent staining (phospho-DIGE). This large-scale phosphoproteome analysis of early OG-signaling enabled us to determine 100 regulated phosphosites using LC-MS/MS and 46 differential spots corresponding to 34 pdhosphoproteins using phospho-DIGE. Functional classification showed that the OG-responsive phosphoproteins include kinases, phosphatases and receptor-like kinases, heat shock proteins (HSPs), reactive oxygen species (ROS) scavenging enzymes, proteins related to cellular trafficking, transport, defense and signaling as well as novel candidates for a role in immunity, for which elicitor-induced phosphorylation changes have not been shown before. A comparison with previously identified elicitor-regulated phosphosites shows only a very limited overlap, uncovering the immune-related regulation of 70 phosphorylation sites and revealing novel potential players in the regulation of elicitor-dependent immunity.
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