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Fujiwara MT, Yoshioka Y, Kazama Y, Hirano T, Niwa Y, Moriyama T, Sato N, Abe T, Yoshida S, Itoh RD. Principles of amyloplast replication in the ovule integuments of Arabidopsis thaliana. PLANT PHYSIOLOGY 2024; 196:137-152. [PMID: 38829834 PMCID: PMC11376375 DOI: 10.1093/plphys/kiae314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 04/30/2024] [Accepted: 05/01/2024] [Indexed: 06/05/2024]
Abstract
Plastids in vascular plants have various differentiated forms, among which amyloplasts are crucial for starch storage and plant productivity. Despite the vast knowledge of the binary-fission mode of chloroplast division, our understanding of the replication of non-photosynthetic plastids, including amyloplasts, remains limited. Recent studies have suggested the involvement of stromules (stroma-filled tubules) in plastid replication when the division apparatus is faulty. However, details of the underlying mechanism(s) and their relevance to normal processes have yet to be elucidated. Here, we developed a live analysis system for studying amyloplast replication using Arabidopsis (Arabidopsis thaliana) ovule integuments. We showed the full sequence of amyloplast development and demonstrated that wild-type amyloplasts adopt three modes of replication, binary fission, multiple fission, and stromule-mediated fission, via multi-way placement of the FtsZ ring. The minE mutant, with severely inhibited chloroplast division, showed marked heterogeneity in amyloplast size, caused by size-dependent but wild-type modes of plastid fission. The dynamic properties of stromules distinguish the wild-type and minE phenotypes. In minE cells, extended stromules from giant amyloplasts acquired stability, allowing FtsZ ring assembly and constriction, as well as the growth of starch grains therein. Despite hyper-stromule formation, amyloplasts did not proliferate in the ftsZ null mutant. These data clarify the differences between amyloplast and chloroplast replication and demonstrate that the structural plasticity of amyloplasts underlies the multiplicity of their replication processes. Furthermore, this study shows that stromules can generate daughter plastids via the assembly of the FtsZ ring.
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Affiliation(s)
- Makoto T Fujiwara
- Nishina Center and Plant Functions Laboratory (Disbanded in March 2004), RIKEN, Wako, Saitama 351-0198, Japan
- Department of Biology, Graduate School of Science and Technology, Sophia University, Kioicho, Chiyoda 102-8554, Japan
- College of Arts and Sciences, University of Tokyo, Komaba, Tokyo 153-8902, Japan
| | - Yasushi Yoshioka
- Graduate School of Science, Nagoya University, Furo-cho, Nagoya 464-8602, Japan
| | - Yusuke Kazama
- Nishina Center and Plant Functions Laboratory (Disbanded in March 2004), RIKEN, Wako, Saitama 351-0198, Japan
| | - Tomonari Hirano
- Nishina Center and Plant Functions Laboratory (Disbanded in March 2004), RIKEN, Wako, Saitama 351-0198, Japan
| | - Yasuo Niwa
- Laboratory of Plant Cell Technology, University of Shizuoka, Yada, Shizuoka 422-8526, Japan
| | - Takashi Moriyama
- College of Arts and Sciences, University of Tokyo, Komaba, Tokyo 153-8902, Japan
| | - Naoki Sato
- College of Arts and Sciences, University of Tokyo, Komaba, Tokyo 153-8902, Japan
| | - Tomoko Abe
- Nishina Center and Plant Functions Laboratory (Disbanded in March 2004), RIKEN, Wako, Saitama 351-0198, Japan
| | - Shigeo Yoshida
- Nishina Center and Plant Functions Laboratory (Disbanded in March 2004), RIKEN, Wako, Saitama 351-0198, Japan
| | - Ryuuichi D Itoh
- Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa 903-0213, Japan
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2
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Erickson JL, Prautsch J, Reynvoet F, Niemeyer F, Hause G, Johnston IG, Schattat MH. Stromule Geometry Allows Optimal Spatial Regulation of Organelle Interactions in the Quasi-2D Cytoplasm. PLANT & CELL PHYSIOLOGY 2024; 65:618-630. [PMID: 37658689 PMCID: PMC11094753 DOI: 10.1093/pcp/pcad098] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Revised: 07/25/2023] [Accepted: 08/29/2023] [Indexed: 09/03/2023]
Abstract
In plant cells, plastids form elongated extensions called stromules, the regulation and purposes of which remain unclear. Here, we quantitatively explore how different stromule structures serve to enhance the ability of a plastid to interact with other organelles: increasing the effective space for interaction and biomolecular exchange between organelles. Interestingly, electron microscopy and confocal imaging showed that the cytoplasm in Arabidopsis thaliana and Nicotiana benthamiana epidermal cells is extremely thin (around 100 nm in regions without organelles), meaning that inter-organelle interactions effectively take place in 2D. We combine these imaging modalities with mathematical modeling and new in planta experiments to demonstrate how different stromule varieties (single or multiple, linear or branching) could be employed to optimize different aspects of inter-organelle interaction capacity in this 2D space. We found that stromule formation and branching provide a proportionally higher benefit to interaction capacity in 2D than in 3D. Additionally, this benefit depends on optimal plastid spacing. We hypothesize that cells can promote the formation of different stromule architectures in the quasi-2D cytoplasm to optimize their interaction interface to meet specific requirements. These results provide new insight into the mechanisms underlying the transition from low to high stromule numbers, the consequences for interaction with smaller organelles, how plastid access and plastid to nucleus signaling are balanced and the impact of plastid density on organelle interaction.
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Affiliation(s)
- Jessica Lee Erickson
- Department of Plant Physiology, Martin-Luther-University Halle-Wittenberg, Weinbergweg 10, Halle 06120, Germany
- Department of Biochemistry of Plant Interactions, Leibniz Institute for Plant Biochemistry, Weinbergweg 10, Halle 06120, Germany
| | - Jennifer Prautsch
- Department of Plant Physiology, Martin-Luther-University Halle-Wittenberg, Weinbergweg 10, Halle 06120, Germany
| | - Frisine Reynvoet
- Department of Plant Physiology, Martin-Luther-University Halle-Wittenberg, Weinbergweg 10, Halle 06120, Germany
| | - Frederik Niemeyer
- Department of Plant Physiology, Martin-Luther-University Halle-Wittenberg, Weinbergweg 10, Halle 06120, Germany
| | - Gerd Hause
- Department of Plant Physiology, Martin-Luther-University Halle-Wittenberg, Weinbergweg 10, Halle 06120, Germany
| | - Iain G Johnston
- Department of Mathematics, University of Bergen, Realfagbygget, Bergen, Vestland 5007, Norway
- Computational Biology Unit, University of Bergen, Høyteknologisenteret, Bergen, Vestland 5006, Norway
| | - Martin Harmut Schattat
- Department of Plant Physiology, Martin-Luther-University Halle-Wittenberg, Weinbergweg 10, Halle 06120, Germany
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3
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Mathur J, Kunjumon TK, Mammone A, Mathur N. Membrane contacts with the endoplasmic reticulum modulate plastid morphology and behaviour. FRONTIERS IN PLANT SCIENCE 2023; 14:1293906. [PMID: 38111880 PMCID: PMC10726010 DOI: 10.3389/fpls.2023.1293906] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 11/20/2023] [Indexed: 12/20/2023]
Abstract
Plastid behaviour often occurs in tandem with endoplasmic reticulum (ER) dynamics. In order to understand the underlying basis for such linked behaviour we have used time-lapse imaging-based analysis of plastid movement and pleomorphy, including the extension and retraction of stromules. Stable transgenic plants that simultaneously express fluorescent fusion proteins targeted to the plastid stroma, and the ER along with BnCLIP1-eGFP, an independent plastid envelope localized membrane contact site (MCS) marker were utilized. Our experiments strongly suggest that transient MCS formed between the plastid envelope and the ER are responsible for their concomitant behaviour.
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Affiliation(s)
- Jaideep Mathur
- Laboratory of Plant Development and Interactions, Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada
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4
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Hsiao AS, Huang JY. Microtubule Regulation in Plants: From Morphological Development to Stress Adaptation. Biomolecules 2023; 13:biom13040627. [PMID: 37189374 DOI: 10.3390/biom13040627] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Revised: 03/09/2023] [Accepted: 03/25/2023] [Indexed: 04/03/2023] Open
Abstract
Microtubules (MTs) are essential elements of the eukaryotic cytoskeleton and are critical for various cell functions. During cell division, plant MTs form highly ordered structures, and cortical MTs guide the cell wall cellulose patterns and thus control cell size and shape. Both are important for morphological development and for adjusting plant growth and plasticity under environmental challenges for stress adaptation. Various MT regulators control the dynamics and organization of MTs in diverse cellular processes and response to developmental and environmental cues. This article summarizes the recent progress in plant MT studies from morphological development to stress responses, discusses the latest techniques applied, and encourages more research into plant MT regulation.
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5
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Itoh RD, Nakajima KP, Sasaki S, Ishikawa H, Kazama Y, Abe T, Fujiwara MT. TGD5 is required for normal morphogenesis of non-mesophyll plastids, but not mesophyll chloroplasts, in Arabidopsis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 107:237-255. [PMID: 33884686 DOI: 10.1111/tpj.15287] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 04/10/2021] [Accepted: 04/13/2021] [Indexed: 06/12/2023]
Abstract
Stromules are dynamic membrane-bound tubular structures that emanate from plastids. Stromule formation is triggered in response to various stresses and during plant development, suggesting that stromules may have physiological and developmental roles in these processes. Despite the possible biological importance of stromules and their prevalence in green plants, their exact roles and formation mechanisms remain unclear. To explore these issues, we obtained Arabidopsis thaliana mutants with excess stromule formation in the leaf epidermis by microscopy-based screening. Here, we characterized one of these mutants, stromule biogenesis altered 1 (suba1). suba1 forms plastids with severely altered morphology in a variety of non-mesophyll tissues, such as leaf epidermis, hypocotyl epidermis, floral tissues, and pollen grains, but apparently normal leaf mesophyll chloroplasts. The suba1 mutation causes impaired chloroplast pigmentation and altered chloroplast ultrastructure in stomatal guard cells, as well as the aberrant accumulation of lipid droplets and their autophagic engulfment by the vacuole. The causal defective gene in suba1 is TRIGALACTOSYLDIACYLGLYCEROL5 (TGD5), which encodes a protein putatively involved in the endoplasmic reticulum (ER)-to-plastid lipid trafficking required for the ER pathway of thylakoid lipid assembly. These findings suggest that a non-mesophyll-specific mechanism maintains plastid morphology. The distinct mechanisms maintaining plastid morphology in mesophyll versus non-mesophyll plastids might be attributable, at least in part, to the differential contributions of the plastidial and ER pathways of lipid metabolism between mesophyll and non-mesophyll plastids.
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Affiliation(s)
- Ryuuichi D Itoh
- Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa, 903-0213, Japan
| | - Kohdai P Nakajima
- Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa, 903-0213, Japan
| | - Shun Sasaki
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda, Tokyo, 102-8554, Japan
| | - Hiroki Ishikawa
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda, Tokyo, 102-8554, Japan
| | - Yusuke Kazama
- Nishina Center, RIKEN, Wako, Saitama, 351-0198, Japan
| | - Tomoko Abe
- Nishina Center, RIKEN, Wako, Saitama, 351-0198, Japan
| | - Makoto T Fujiwara
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda, Tokyo, 102-8554, Japan
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6
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Mathur J. Organelle extensions in plant cells. PLANT PHYSIOLOGY 2021; 185:593-607. [PMID: 33793902 PMCID: PMC8133556 DOI: 10.1093/plphys/kiaa055] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 09/15/2020] [Indexed: 05/03/2023]
Abstract
The life strategy of plants includes their ability to respond quickly at the cellular level to changes in their environment. The use of targeted fluorescent protein probes and imaging of living cells has revealed several rapidly induced organelle responses that create the efficient sub-cellular machinery for maintaining homeostasis in the plant cell. Several organelles, including plastids, mitochondria, and peroxisomes, extend and retract thin tubules that have been named stromules, matrixules, and peroxules, respectively. Here, I combine all these thin tubular forms under the common head of organelle extensions. All extensions change shape continuously and in their elongated form considerably increase organelle outreach into the surrounding cytoplasm. Their pleomorphy reflects their interactions with the dynamic endoplasmic reticulum and cytoskeletal elements. Here, using foundational images and time-lapse movies, and providing salient information on some molecular and biochemically characterized mutants with increased organelle extensions, I draw attention to their common role in maintaining homeostasis in plant cells.
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Affiliation(s)
- Jaideep Mathur
- Laboratory of Plant Development and Interactions, Department of Molecular and Cellular biology, University of Guelph, 50 Stone Road, Guelph, Ontario, N1G2W1 Canada
- Author for communication:
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Cecchini NM, Speed DJ, Roychoudhry S, Greenberg JT. Kinases and protein motifs required for AZI1 plastid localization and trafficking during plant defense induction. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 105:1615-1629. [PMID: 33342031 PMCID: PMC8048937 DOI: 10.1111/tpj.15137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 12/14/2020] [Accepted: 12/15/2020] [Indexed: 05/10/2023]
Abstract
The proper subcellular localization of defense factors is an important part of the plant immune system. A key component for systemic resistance, lipid transfer protein (LTP)-like AZI1, is needed for the systemic movement of the priming signal azelaic acid (AZA) and a pool of AZI1 exists at the site of AZA production, the plastid envelope. Moreover, after systemic defense-triggering infections, the proportion of AZI1 localized to plastids increases. However, AZI1 does not possess a classical plastid transit peptide that can explain its localization. Instead, AZI1 uses a bipartite N-terminal signature that allows for its plastid targeting. Furthermore, the kinases MPK3 and MPK6, associated with systemic immunity, promote the accumulation of AZI1 at plastids during priming induction. Our results indicate the existence of a mode of plastid targeting possibly related to defense responses.
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Affiliation(s)
- Nicolás M. Cecchini
- Department of Molecular Genetics and Cell BiologyThe University of Chicago929 East 57th Street GCIS 524WChicagoIL60637USA
- Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC‐CONICET) and Departamento de Química Biológica Ranwel CaputtoFacultad de Ciencias QuímicasUniversidad Nacional de CórdobaHaya de la Torre y Medina Allende – Ciudad UniversitariaCórdobaX5000HUAArgentina
| | - DeQuantarius J. Speed
- Department of Molecular Genetics and Cell BiologyThe University of Chicago929 East 57th Street GCIS 524WChicagoIL60637USA
| | - Suruchi Roychoudhry
- Department of Molecular Genetics and Cell BiologyThe University of Chicago929 East 57th Street GCIS 524WChicagoIL60637USA
- Centre for Plant SciencesUniversity of LeedsLeedsLS2 9JTUK
| | - Jean T. Greenberg
- Department of Molecular Genetics and Cell BiologyThe University of Chicago929 East 57th Street GCIS 524WChicagoIL60637USA
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8
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Hanson MR, Conklin PL. Stromules, functional extensions of plastids within the plant cell. CURRENT OPINION IN PLANT BIOLOGY 2020; 58:25-32. [PMID: 33137706 DOI: 10.1016/j.pbi.2020.10.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Revised: 10/11/2020] [Accepted: 10/12/2020] [Indexed: 06/11/2023]
Abstract
Stromules are thin tubular extensions of the plastid compartment surrounded by the envelope membrane. A myriad of functions have been proposed for them, and they likely have multiple roles. Recent work has illuminated aspects of their formation, especially the important of microtubules in their movement and microfilaments in anchoring. A variety of biotic and abiotic stresses result in induction of stromule formation, and in recent years, stromule formation has been strongly implicated as part of the innate immune response. Both stromules and chloroplasts relocate to surround the nucleus when pathogens are sensed, possibly to supply signaling molecules such as reactive oxygen species. In addition to the nucleus, stromules have been observed in close proximity to other compartments such as mitochondria, endoplasmic reticulum, and the plasma membrane, potentially facilitating exchange of substrates and products to carry out important biosynthetic pathways. Much remains to be learned about the identity of proteins and other molecules released from chloroplasts and stromules and how they function in plant development and defense.
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Affiliation(s)
- Maureen R Hanson
- Department of Molecular Biology and Genetics, Biotechnology Building, Cornell University, Ithaca, NY 14853, USA.
| | - Patricia L Conklin
- Biological Sciences Department, State University of New York, Cortland, NY 13045, USA
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9
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Gronnier J, Legrand A, Loquet A, Habenstein B, Germain V, Mongrand S. Mechanisms governing subcompartmentalization of biological membranes. CURRENT OPINION IN PLANT BIOLOGY 2019; 52:114-123. [PMID: 31546133 DOI: 10.1016/j.pbi.2019.08.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Revised: 08/14/2019] [Accepted: 08/20/2019] [Indexed: 06/10/2023]
Abstract
Membranes show a tremendous variety of lipids and proteins operating biochemistry, transport and signalling. The dynamics and the organization of membrane constituents are regulated in space and time to execute precise functions. Our understanding of the molecular mechanisms that shape and govern membrane subcompartmentalization and inter-organelle contact sites still remains limited. Here, we review some reported mechanisms implicated in regulating plant membrane domains including those of plasma membrane, plastids, mitochondria and endoplasmic reticulum. Finally, we discuss several state-of-the-art methods that allow nowadays researchers to decipher the architecture of these structures at the molecular and atomic level.
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Affiliation(s)
- Julien Gronnier
- Department of Plant and Microbial Biology, Zurich-Basel Plant Science Center, University of Zürich, Zürich, Switzerland
| | - Anthony Legrand
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse Membranaire (LBM), UMR 5200, 33140 Villenave d'Ornon, France; Institute of Chemistry & Biology of Membranes & Nanoobjects (UMR5248 CBMN), IECB, CNRS, Université de Bordeaux, Institut Polytechnique de Bordeaux, All, Geoffroy Saint-Hilaire, Pessac, France
| | - Antoine Loquet
- Institute of Chemistry & Biology of Membranes & Nanoobjects (UMR5248 CBMN), IECB, CNRS, Université de Bordeaux, Institut Polytechnique de Bordeaux, All, Geoffroy Saint-Hilaire, Pessac, France
| | - Birgit Habenstein
- Institute of Chemistry & Biology of Membranes & Nanoobjects (UMR5248 CBMN), IECB, CNRS, Université de Bordeaux, Institut Polytechnique de Bordeaux, All, Geoffroy Saint-Hilaire, Pessac, France
| | - Véronique Germain
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse Membranaire (LBM), UMR 5200, 33140 Villenave d'Ornon, France
| | - Sébastien Mongrand
- Univ. Bordeaux, CNRS, Laboratoire de Biogenèse Membranaire (LBM), UMR 5200, 33140 Villenave d'Ornon, France.
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Fujiwara MT, Sanjaya A, Itoh RD. Arabidopsis thaliana Leaf Epidermal Guard Cells: A Model for Studying Chloroplast Proliferation and Partitioning in Plants. FRONTIERS IN PLANT SCIENCE 2019; 10:1403. [PMID: 31737018 PMCID: PMC6831612 DOI: 10.3389/fpls.2019.01403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 10/10/2019] [Indexed: 05/29/2023]
Abstract
The existence of numerous chloroplasts in photosynthetic cells is a general feature of plants. Chloroplast biogenesis and inheritance involve two distinct mechanisms: proliferation of chloroplasts by binary fission and partitioning of chloroplasts into daughter cells during cell division. The mechanism of chloroplast number coordination in a given cell type is a fundamental question. Stomatal guard cells (GCs) in the plant shoot epidermis generally contain several to tens of chloroplasts per cell. Thus far, chloroplast number at the stomatal (GC pair) level has generally been used as a convenient marker for identifying hybrid species or estimating the ploidy level of a given plant tissue. Here, we report that Arabidopsis thaliana leaf GCs represent a useful system for investigating the unexploited aspects of chloroplast number control in plant cells. In contrast to a general notion based on analyses of leaf mesophyll chloroplasts, a small difference was detected in the GC chloroplast number among three Arabidopsis ecotypes (Columbia, Landsberg erecta, and Wassilewskija). Fluorescence microscopy often detected dividing GC chloroplasts with the FtsZ1 ring not only at the early stage of leaf expansion but also at the late stage. Compensatory chloroplast expansion, a phenomenon well documented in leaf mesophyll cells of chloroplast division mutants and transgenic plants, could take place between paired GCs in wild-type leaves. Furthermore, modest chloroplast number per GC as well as symmetric division of guard mother cells for GC formation suggests that Arabidopsis GCs would facilitate the analysis of chloroplast partitioning, based on chloroplast counting at the individual cell level.
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Affiliation(s)
- Makoto T. Fujiwara
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, Tokyo, Japan
| | - Alvin Sanjaya
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, Tokyo, Japan
| | - Ryuuichi D. Itoh
- Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Nishihara, Japan
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11
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Ishikawa H, Yasuzawa M, Koike N, Sanjaya A, Moriyama S, Nishizawa A, Matsuoka K, Sasaki S, Kazama Y, Hayashi Y, Abe T, Fujiwara MT, Itoh RD. Arabidopsis PARC6 Is Critical for Plastid Morphogenesis in Pavement, Trichome, and Guard Cells in Leaf Epidermis. FRONTIERS IN PLANT SCIENCE 2019; 10:1665. [PMID: 32010156 PMCID: PMC6974557 DOI: 10.3389/fpls.2019.01665] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Accepted: 11/26/2019] [Indexed: 05/20/2023]
Abstract
Recently, a recessive Arabidopsis thaliana mutant with abundant stromules in leaf epidermal pavement cells was visually screened and isolated. The gene responsible for this mutant phenotype was identified as PARC6, a chloroplast division site regulator gene. The mutant allele parc6-5 carried two point mutations (G62R and W700stop) at the N- and C-terminal ends of the coding sequence, respectively. Here, we further characterized parc6-5 and other parc6 mutant alleles, and showed that PARC6 plays a critical role in plastid morphogenesis in all cell types of the leaf epidermis: pavement cells, trichome cells, and guard cells. Transient expression of PARC6 transit peptide (TP) fused to the green fluorescent protein (GFP) in plant cells showed that the G62R mutation has no or little effect on the TP activity of the PARC6 N-terminal region. Then, plastid morphology was microscopically analyzed in the leaf epidermis of wild-type (WT) and parc6 mutants (parc6-1, parc6-3, parc6-4 and parc6-5) with the aid of stroma-targeted fluorescent proteins. In parc6 pavement cells, plastids often assumed aberrant grape-like morphology, similar to those in severe plastid division mutants, atminE1, and arc6. In parc6 trichome cells, plastids exhibited extreme grape-like aggregations, without the production of giant plastids (>6 µm diameter), as a general phenotype. In parc6 guard cells, plastids exhibited a variety of abnormal phenotypes, including reduced number, enlarged size, and activated stromules, similar to those in atminE1 and arc6 guard cells. Nevertheless, unlike atminE1 and arc6, parc6 exhibited a low number of mini-chloroplasts (< 2 µm diameter) and rarely produced chloroplast-deficient guard cells. Importantly, unlike parc6, the chloroplast division site mutant arc11 exhibited WT-like plastid phenotypes in trichome and guard cells. Finally, observation of parc6 complementation lines expressing a functional PARC6-GFP protein indicated that PARC6-GFP formed a ring-like structure in both constricting and non-constricting chloroplasts, and that PARC6 dynamically changes its configuration during the process of chloroplast division.
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Affiliation(s)
- Hiroki Ishikawa
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, Tokyo, Japan
| | - Mana Yasuzawa
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, Tokyo, Japan
| | - Nana Koike
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, Tokyo, Japan
| | - Alvin Sanjaya
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, Tokyo, Japan
| | - Shota Moriyama
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, Tokyo, Japan
| | - Aya Nishizawa
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, Tokyo, Japan
| | - Kanae Matsuoka
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, Tokyo, Japan
| | - Shun Sasaki
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, Tokyo, Japan
| | - Yusuke Kazama
- Nishina Center for Accelerator-Based Science, RIKEN, Wako, Japan
| | - Yoriko Hayashi
- Nishina Center for Accelerator-Based Science, RIKEN, Wako, Japan
| | - Tomoko Abe
- Nishina Center for Accelerator-Based Science, RIKEN, Wako, Japan
| | - Makoto T. Fujiwara
- Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, Tokyo, Japan
- Nishina Center for Accelerator-Based Science, RIKEN, Wako, Japan
| | - Ryuuichi D. Itoh
- Department of Chemistry, Biology and Marine Science, Faculty of Science, University of the Ryukyus, Okinawa, Japan
- *Correspondence: Ryuuichi D. Itoh,
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