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Mizuta Y. Advances in Two-Photon Imaging in Plants. PLANT & CELL PHYSIOLOGY 2021; 62:1224-1230. [PMID: 34019083 PMCID: PMC8579158 DOI: 10.1093/pcp/pcab062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Revised: 03/16/2021] [Accepted: 05/20/2021] [Indexed: 05/06/2023]
Abstract
Live and deep imaging play a significant role in the physiological and biological study of organisms. Two-photon excitation microscopy (2PEM), also known as multiphoton excitation microscopy, is a fluorescent imaging technique that allows deep imaging of living tissues. Two-photon lasers use near-infrared (NIR) pulse lasers that are less invasive and permit deep tissue penetration. In this review, recent advances in two-photon imaging and their applications in plant studies are discussed. Compared to confocal microscopy, NIR 2PEM exhibits reduced plant-specific autofluorescence, thereby achieving greater depth and high-resolution imaging in plant tissues. Fluorescent proteins with long emission wavelengths, such as orange-red fluorescent proteins, are particularly suitable for two-photon live imaging in plants. Furthermore, deep- and high-resolution imaging was achieved using plant-specific clearing methods. In addition to imaging, optical cell manipulations can be performed using femtosecond pulsed lasers at the single cell or organelle level. Optical surgery and manipulation can reveal cellular communication during development. Advances in in vivo imaging using 2PEM will greatly benefit biological studies in plant sciences.
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Affiliation(s)
- Yoko Mizuta
- Institute for Advanced Research (IAR), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan
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Ali MF, Fatema U, Peng X, Hacker SW, Maruyama D, Sun MX, Kawashima T. ARP2/3-independent WAVE/SCAR pathway and class XI myosin control sperm nuclear migration in flowering plants. Proc Natl Acad Sci U S A 2020; 117:32757-32763. [PMID: 33288691 PMCID: PMC7768783 DOI: 10.1073/pnas.2015550117] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
After eukaryotic fertilization, gamete nuclei migrate to fuse parental genomes in order to initiate development of the next generation. In most animals, microtubules control female and male pronuclear migration in the zygote. Flowering plants, on the other hand, have evolved actin filament (F-actin)-based sperm nuclear migration systems for karyogamy. Flowering plants have also evolved a unique double-fertilization process: two female gametophytic cells, the egg and central cells, are each fertilized by a sperm cell. The molecular and cellular mechanisms of how flowering plants utilize and control F-actin for double-fertilization events are largely unknown. Using confocal microscopy live-cell imaging with a combination of pharmacological and genetic approaches, we identified factors involved in F-actin dynamics and sperm nuclear migration in Arabidopsis thaliana (Arabidopsis) and Nicotiana tabacum (tobacco). We demonstrate that the F-actin regulator, SCAR2, but not the ARP2/3 protein complex, controls the coordinated active F-actin movement. These results imply that an ARP2/3-independent WAVE/SCAR-signaling pathway regulates F-actin dynamics in female gametophytic cells for fertilization. We also identify that the class XI myosin XI-G controls active F-actin movement in the Arabidopsis central cell. XI-G is not a simple transporter, moving cargos along F-actin, but can generate forces that control the dynamic movement of F-actin for fertilization. Our results provide insights into the mechanisms that control gamete nuclear migration and reveal regulatory pathways for dynamic F-actin movement in flowering plants.
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Affiliation(s)
- Mohammad Foteh Ali
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546-0312
| | - Umma Fatema
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546-0312
| | - Xiongbo Peng
- State Key Laboratory of Hybrid Rice, College of Life Science, Wuhan University, 430072 Wuhan, China
| | - Samuel W Hacker
- Agriculture and Medical Biotechnology Program, University of Kentucky, Lexington, KY 40546-0312
| | - Daisuke Maruyama
- Kihara Institute for Biological Research, Yokohama City University, 244-0813 Yokohama, Kanagawa, Japan
| | - Meng-Xiang Sun
- State Key Laboratory of Hybrid Rice, College of Life Science, Wuhan University, 430072 Wuhan, China
| | - Tomokazu Kawashima
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546-0312;
- Agriculture and Medical Biotechnology Program, University of Kentucky, Lexington, KY 40546-0312
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Li HJ, Yang WC. Central Cell in Flowering Plants: Specification, Signaling, and Evolution. FRONTIERS IN PLANT SCIENCE 2020; 11:590307. [PMID: 33193544 PMCID: PMC7609669 DOI: 10.3389/fpls.2020.590307] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Accepted: 09/28/2020] [Indexed: 05/05/2023]
Abstract
During the reproduction of animals and lower plants, one sperm cell usually outcompetes the rivals to fertilize a single egg cell. But in flowering plants, two sperm cells fertilize the two adjacent dimorphic female gametes, the egg and central cell, respectively, to initiate the embryo and endosperm within a seed. The endosperm nourishes the embryo development and is also the major source of nutrition in cereals for humankind. Central cell as one of the key innovations of flowering plants is the biggest cell in the multicellular haploid female gametophyte (embryo sac). The embryo sac differentiates from the meiotic products through successive events of nuclear divisions, cellularization, and cell specification. Nowadays, accumulating lines of evidence are raveling multiple roles of the central cell rather than only the endosperm precursor. In this review, we summarize the current understanding on its cell fate specification, intercellular communication, and evolution. We also highlight some key unsolved questions for the further studies in this field.
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Affiliation(s)
- Hong-Ju Li
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
| | - Wei-Cai Yang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
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Nishikawa SI, Yamaguchi Y, Suzuki C, Yabe A, Sato Y, Kurihara D, Sato Y, Susaki D, Higashiyama T, Maruyama D. Arabidopsis GEX1 Is a Nuclear Membrane Protein of Gametes Required for Nuclear Fusion During Reproduction. FRONTIERS IN PLANT SCIENCE 2020; 11:548032. [PMID: 33154760 PMCID: PMC7586128 DOI: 10.3389/fpls.2020.548032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 09/15/2020] [Indexed: 05/25/2023]
Abstract
During the life cycle of flowering plants, nuclear fusion, or karyogamy, occurs three times: once during female gametogenesis, when the two polar nuclei fuse in the central cell, and twice during double fertilization. In Arabidopsis thaliana, nuclear fusion events during sexual reproduction proceed without the breakdown of the nuclear envelope, indicating that nuclear membrane fusion is essential for the completion of this process. Arabidopsis gamete expressed 1 (GEX1) is a membrane protein that is conserved among plant species. GEX1 shares homology with the yeast karyogamy protein Kar5, which is primarily expressed in the nuclear membrane. The GEX1 family represents a putative karyogamy factor. Herein, we show that GEX1 is required for the nuclear fusion events in Arabidopsis reproduction. GEX1-deficient mature female gametophytes were found to contain two unfused polar nuclei in close proximity within the central cell. Electron microscopy showed that the outer membrane of the polar nuclei was connected via the endoplasmic reticulum, whereas the inner membrane remained unfused. These results indicate that GEX1 is involved in polar nuclear membrane fusion following the fusion of the outer nuclear membrane. Furthermore, sperm nuclear fusion events were defective in the fertilized egg and central cell following plasmogamy in the fertilization of gex1-1 female gametophytes by gex1-1 pollen. An analysis of GEX1 localization in the female gametophyte using a transgenic line expressing GFP-tagged GEX1 driven by the GEX1 promoter showed that GEX1 is a nuclear membrane protein in the egg and central cell. Time-lapse live-cell imaging showed that in developing female gametophytes, the nuclear GFP-GEX1 signal was first detectable in the central cell shortly before the polar nuclei came in close contact, and then in the egg cell. Thus, we suggest that the GEX1-family proteins are nuclear membrane proteins involved in karyogamy in the reproduction of eukaryotes including flowering plants.
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Affiliation(s)
| | - Yuki Yamaguchi
- Graduate School of Science and Technology, Niigata University, Niigata, Japan
| | - Chiharu Suzuki
- Graduate School of Science and Technology, Niigata University, Niigata, Japan
| | - Ayaka Yabe
- Graduate School of Science and Technology, Niigata University, Niigata, Japan
| | - Yuzuru Sato
- Biology Program, Faculty of Science, Niigata University, Niigata, Japan
| | - Daisuke Kurihara
- Japan Science and Technology Agency, PRESTO, Nagoya, Japan
- Institute of Transformative Bio-Molecules, Nagoya University, Nagoya, Japan
| | - Yoshikatsu Sato
- Institute of Transformative Bio-Molecules, Nagoya University, Nagoya, Japan
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Daichi Susaki
- Kihara Institute for Biological Research, Yokohama City University, Yokohama, Japan
| | - Tetsuya Higashiyama
- Institute of Transformative Bio-Molecules, Nagoya University, Nagoya, Japan
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan
- Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo, Japan
| | - Daisuke Maruyama
- Kihara Institute for Biological Research, Yokohama City University, Yokohama, Japan
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