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Zhong S, Zhao P, Peng X, Li HJ, Duan Q, Cheung AY. From gametes to zygote: Mechanistic advances and emerging possibilities in plant reproduction. PLANT PHYSIOLOGY 2024; 195:4-35. [PMID: 38431529 PMCID: PMC11060694 DOI: 10.1093/plphys/kiae125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 02/13/2024] [Accepted: 02/13/2024] [Indexed: 03/05/2024]
Affiliation(s)
- Sheng Zhong
- State Key Laboratory for Protein and Plant Gene Research, Peking-Tsinghua Center for Life Sciences, New Cornerstone Science Laboratory, College of Life Sciences, Peking University, Beijing 100871, China
| | - Peng Zhao
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Xiongbo Peng
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
- Hubei Hongshan Laboratory, Wuhan 430070, China
| | - Hong-Ju Li
- Key Laboratory of Seed Innovation, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Center for Molecular Agrobiology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
| | - Qiaohong Duan
- College of Horticulture Science and Engineering, Shandong Agricultural University, Tai’an, Shandong 271018, China
| | - Alice Y Cheung
- Department of Biochemistry and Molecular Biology, Molecular and Cellular Biology Program, Plant Biology Graduate Program, University of Massachusetts, Amherst, MA 01003, USA
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Watanabe Y, Nobe Y, Taoka M, Okamoto T. The Feeder Effects of Cultured Rice Cells on the Early Development of Rice Zygotes. Int J Mol Sci 2023; 24:16541. [PMID: 38003730 PMCID: PMC10672051 DOI: 10.3390/ijms242216541] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 11/13/2023] [Accepted: 11/16/2023] [Indexed: 11/26/2023] Open
Abstract
Feeder cells and the synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) in a culture medium promote mitosis and cell division in cultured cells. These are also added to nutrient medium for the cultivation of highly active in mitosis and dividing zygotes, produced in vitro or isolated from pollinated ovaries. In the study, an in vitro fertilization (IVF) system was used to study the precise effects of feeder cells and 2,4-D on the growth and development of rice (Oryza sativa L.) zygote. The elimination of 2,4-D from the culture medium did not affect the early developmental profiles of the zygotes, but decreased the division rates of multicellular embryos. The omission of feeder cells resulted in defective karyogamy, fusion between male and female nuclei, and the subsequent first division of the cultured zygotes. The culture of zygotes in a conditioned medium corrected developmental disorders. Proteome analyses of the conditioned medium revealed the presence of abundant hydrolases possibly released from the feeder cells. Exogenously applied α-amylase ameliorated karyogamy and promoted zygote development. It is suggested that hydrolytic enzymes, including α-amylase, released from feeder cells may be involved in the progression of zygotic development.
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Affiliation(s)
- Yoriko Watanabe
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji 192-0397, Tokyo, Japan;
| | - Yuko Nobe
- Department of Chemistry, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji 192-0397, Tokyo, Japan; (Y.N.); (M.T.)
| | - Masato Taoka
- Department of Chemistry, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji 192-0397, Tokyo, Japan; (Y.N.); (M.T.)
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachioji 192-0397, Tokyo, Japan;
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Kobayashi N, Nishikawa SI. Nuclear Fusion in Yeast and Plant Reproduction. PLANTS (BASEL, SWITZERLAND) 2023; 12:3608. [PMID: 37896071 PMCID: PMC10609895 DOI: 10.3390/plants12203608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 10/09/2023] [Accepted: 10/16/2023] [Indexed: 10/29/2023]
Abstract
Nuclear fusion is essential for the sexual reproduction of various organisms, including plants, animals, and fungi. During the life cycle of flowering plants, nuclear fusion occurs three times: once during female gametogenesis and twice during double fertilization, when two sperm cells fertilize the egg and the central cell. Haploid nuclei migrate in an actin filament-dependent manner to become in close contact and, then, two nuclei fuse. The nuclear fusion process in plant reproduction is achieved through sequential nuclear membrane fusion events. Recent molecular genetic analyses using Arabidopsis thaliana showed the conservation of nuclear membrane fusion machinery between plants and the budding yeast Saccharomyces cerevisiae. These include the heat-shock protein 70 in the endoplasmic reticulum and the conserved nuclear membrane proteins. Analyses of the A. thaliana mutants of these components show that the completion of the sperm nuclear fusion at fertilization is essential for proper embryo and endosperm development.
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Affiliation(s)
- Nanami Kobayashi
- Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan;
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Susaki D, Izumi R, Oi T, Takeuchi H, Shin JM, Sugi N, Kinoshita T, Higashiyama T, Kawashima T, Maruyama D. F-actin regulates the polarized secretion of pollen tube attractants in Arabidopsis synergid cells. THE PLANT CELL 2023; 35:1222-1240. [PMID: 36562145 PMCID: PMC10052382 DOI: 10.1093/plcell/koac371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Accepted: 12/15/2022] [Indexed: 06/17/2023]
Abstract
Pollen tube attraction is a key event of sexual reproduction in flowering plants. In the ovule, two synergid cells neighboring the egg cell control pollen tube arrival via the active secretion of attractant peptides such as AtLURE1 and XIUQIU from the filiform apparatus (FA) facing toward the micropyle. Distinctive cell polarity together with longitudinal F-actin and microtubules are hallmarks of the synergid cell in various species, though the functions of these cellular structures are unclear. In this study, we used genetic and pharmacological approaches to indicate the roles of cytoskeletal components in FA formation and pollen tube guidance in Arabidopsis thaliana. Genetic inhibition of microtubule formation reduced invaginations of the plasma membrane but did not abolish micropylar AtLURE1.2 accumulation. By contrast, the expression of a dominant-negative form of ACTIN8 induced disorganization of the FA and loss of polar AtLURE1.2 distribution toward the FA. Interestingly, after pollen tube reception, F-actin became unclear for a few hours in the persistent synergid cell, which may be involved in pausing and resuming pollen tube attraction during early polytubey block. Our data suggest that F-actin plays a central role in maintaining cell polarity and in mediating male-female communication in the synergid cell.
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Affiliation(s)
- Daichi Susaki
- Kihara Institute for Biological Research, Yokohama City University, Maioka-cho 641-12, Totsuka-ku, Yokohama, Kanagawa, 244-0813, Japan
| | - Rie Izumi
- Kihara Institute for Biological Research, Yokohama City University, Maioka-cho 641-12, Totsuka-ku, Yokohama, Kanagawa, 244-0813, Japan
| | - Takao Oi
- Graduate school of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
| | - Hidenori Takeuchi
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan
- Institute for Advanced Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan
| | - Ji Min Shin
- Department of Plant and Soil Sciences, University of Kentucky, 321 Plant Science Building, Lexington, Kentucky 40546, USA
| | - Naoya Sugi
- Kihara Institute for Biological Research, Yokohama City University, Maioka-cho 641-12, Totsuka-ku, Yokohama, Kanagawa, 244-0813, Japan
| | - Tetsu Kinoshita
- Kihara Institute for Biological Research, Yokohama City University, Maioka-cho 641-12, Totsuka-ku, Yokohama, Kanagawa, 244-0813, Japan
| | - Tetsuya Higashiyama
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Tomokazu Kawashima
- Department of Plant and Soil Sciences, University of Kentucky, 321 Plant Science Building, Lexington, Kentucky 40546, USA
| | - Daisuke Maruyama
- Kihara Institute for Biological Research, Yokohama City University, Maioka-cho 641-12, Totsuka-ku, Yokohama, Kanagawa, 244-0813, Japan
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Shin JM, Yuan L, Kawashima T. Live-cell imaging reveals the cellular dynamics in seed development. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2022; 325:111485. [PMID: 36206961 DOI: 10.1016/j.plantsci.2022.111485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 09/28/2022] [Accepted: 09/30/2022] [Indexed: 06/16/2023]
Abstract
Seed development in flowering plants is highly complex and governed by three genetically distinct tissues: the fertilization products, the diploid embryo and triploid endosperm, as well as the seed coat that has maternal origin. There are diverse cellular dynamics such as nuclear movement in gamete cells for fertilization, cell polarity establishment for embryo development, and multinuclear endosperm formation. These tissues also coordinate and synchronize the developmental timing for proper seed formation through cell-to-cell communications. Live-cell imaging using advanced microscopy techniques enables us to decipher the dynamics of these events. Especially, the establishment of a less-invasive semi-in vivo live-cell imaging approach has allowed us to perform time-lapse analyses for long period observation of Arabidopsis thaliana intact seed development dynamics. Here we highlight the recent trends of live-cell imaging for seed development and discuss where we are heading.
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Affiliation(s)
- Ji Min Shin
- Department of Plant and Soil Sciences, University of Kentucky, KY, USA; Kentucky Tobacco Research and Development Center, University of Kentucky, KY, USA
| | - Ling Yuan
- Department of Plant and Soil Sciences, University of Kentucky, KY, USA; Kentucky Tobacco Research and Development Center, University of Kentucky, KY, USA
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Chahal LS, Conner JA, Ozias-Akins P. Phylogenetically Distant BABY BOOM Genes From Setaria italica Induce Parthenogenesis in Rice. FRONTIERS IN PLANT SCIENCE 2022; 13:863908. [PMID: 35909735 PMCID: PMC9329937 DOI: 10.3389/fpls.2022.863908] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Accepted: 06/13/2022] [Indexed: 06/02/2023]
Abstract
The combination of apomixis and hybrid production is hailed as the holy grail of agriculture for the ability of apomixis to fix heterosis of F1 hybrids in succeeding generations, thereby eliminating the need for repeated crosses to produce F1 hybrids. Apomixis, asexual reproduction through seed, achieves this feat by circumventing two processes that are fundamental to sexual reproduction (meiosis and fertilization) and replacing them with apomeiosis and parthenogenesis, resulting in seeds that are clonal to the maternal parent. Parthenogenesis, embryo development without fertilization, has been genetically engineered in rice, maize, and pearl millet using PsASGR-BABY BOOM-like (PsASGR-BBML) transgenes and in rice using the OsBABY BOOM1 (OsBBM1) cDNA sequence when expressed under the control of egg cell-specific promoters. A phylogenetic analysis revealed that BABY BOOM (BBM)/BBML genes from monocots cluster within three different clades. The BBM/BBML genes shown to induce parthenogenesis cluster within clade 1 (the ASGR-BBML clade) along with orthologs from other monocot species, such as Setaria italica. For this study, we tested the parthenogenetic potential of three BBM transgenes from S. italica, each a member of a different phylogenetic BBM clade. All transgenes were genomic constructs under the control of the AtDD45 egg cell-specific promoter. All SiBBM transgenes induced various levels of parthenogenetic embryo development, resulting in viable haploid T1 seedlings. Poor seed set and lower haploid seed production were characteristics of multiple transgenic lines. The results presented in this study illustrate that further functional characterization of BBMs in zygote/embryo development is warranted.
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Affiliation(s)
- Lovepreet Singh Chahal
- Institute of Plant Breeding, Genetics, and Genomics, University of Georgia, Tifton, GA, United States
| | - Joann A. Conner
- Institute of Plant Breeding, Genetics, and Genomics, University of Georgia, Tifton, GA, United States
- Department of Horticulture, University of Georgia, Tifton, GA, United States
| | - Peggy Ozias-Akins
- Institute of Plant Breeding, Genetics, and Genomics, University of Georgia, Tifton, GA, United States
- Department of Horticulture, University of Georgia, Tifton, GA, United States
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Toda E, Kiba T, Kato N, Okamoto T. Isolation of gametes and zygotes from Setaria viridis. JOURNAL OF PLANT RESEARCH 2022; 135:627-633. [PMID: 35534650 DOI: 10.1007/s10265-022-01393-w] [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: 02/20/2022] [Accepted: 04/25/2022] [Indexed: 06/14/2023]
Abstract
Setaria viridis, the wild ancestor of foxtail millet (Setaria italica), is an effective model plant for larger C4 crops because S. viridis has several desirable traits, such as short generation time, prolific seed production and a small genome size. These advantages are well suited for investigating molecular mechanisms in angiosperms, especially C4 crop species. Here, we report a procedure for isolating gametes and zygotes from S. viridis flowers. To isolate egg cells, ovaries were harvested from unpollinated mature flowers and cut transversely, which allowed direct access to the embryo sac. Thereafter, an egg cell was released from the cut end of the basal portion of the dissected ovary. To isolate sperm cells, pollen grains released from anthers were immersed in a mannitol solution, resulting in pollen-grain bursting, which released sperm cells. Additionally, S. viridis zygotes were successfully isolated from freshly pollinated flowers. Isolated zygotes cultured in a liquid medium developed into globular-like embryos and cell masses. Thus, isolated S. viridis gametes, zygotes and embryos are attainable for detailed observations and investigations of fertilization and developmental events in angiosperms.
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Affiliation(s)
- Erika Toda
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Technology and Innovation Hub, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan.
- Department of Biological Sciences, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji, Tokyo, 192-0392, Japan.
- Department of Biological Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
| | - Takatoshi Kiba
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Technology and Innovation Hub, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan
- Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8601, Japan
| | - Norio Kato
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Technology and Innovation Hub, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan
- Department of Biological Sciences, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji, Tokyo, 192-0392, Japan
| | - Takashi Okamoto
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Technology and Innovation Hub, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045, Japan
- Department of Biological Sciences, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji, Tokyo, 192-0392, Japan
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Yin PP, Tang LP, Zhang XS, Su YH. Options for Engineering Apomixis in Plants. FRONTIERS IN PLANT SCIENCE 2022; 13:864987. [PMID: 35371148 PMCID: PMC8967160 DOI: 10.3389/fpls.2022.864987] [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: 01/29/2022] [Accepted: 02/24/2022] [Indexed: 06/14/2023]
Abstract
In plants, embryogenesis and reproduction are not strictly dependent on fertilization. Several species can produce embryos in seeds asexually, a process known as apomixis. Apomixis is defined as clonal asexual reproduction through seeds, whereby the progeny is identical to the maternal genotype, and provides valuable opportunities for developing superior cultivars, as its induction in agricultural crops can facilitate the development and maintenance of elite hybrid genotypes. In this review, we summarize the current understanding of apomixis and highlight the successful introduction of apomixis methods into sexual crops. In addition, we discuss several genes whose overexpression can induce somatic embryogenesis as candidate genes to induce parthenogenesis, a unique reproductive method of gametophytic apomixis. We also summarize three schemes to achieve engineered apomixis, which will offer more opportunities for the realization of apomictic reproduction.
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Affiliation(s)
| | | | - Xian Sheng Zhang
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai' an, China
| | - Ying Hua Su
- State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai' an, China
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Aini H, Sato Y, Uno K, Higashiyama T, Okamoto T. Dynamics of mitochondrial distribution during development and asymmetric division of rice zygotes. PLANT REPRODUCTION 2022; 35:47-60. [PMID: 34633536 DOI: 10.1007/s00497-021-00430-3] [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: 07/15/2021] [Accepted: 10/01/2021] [Indexed: 06/13/2023]
Abstract
Mitochondria change their distribution from nuclear peripheral to uniformly distributed in cytoplasm during zygotic development of rice, and the mitochondria re-distribute around nucleus for even segregation into daughter cells. Mitochondria are highly dynamic organelles that actively move and change their localization along with actin filaments during the cell cycle. Studies of mitochondrial dynamics and distribution in plant cells have mainly been conducted on somatic cells, and our understanding about these aspects during the formation and development of zygotes remains limited. In this study, mitochondrial nucleoids of rice egg cells and zygotes were successfully stained by using N-aryl pyrido cyanine 3 (PC3), and their intracellular localization and distribution were demonstrated. Mitochondria in rice egg cells were small and coccoid in shape and were primarily distributed around the nucleus. Upon gamete fusion, the resulting zygotes showed mitochondrial dispersion and accumulation equivalent to those in rice egg cells until 8 h after fusion (HAF). Around 12 HAF, the mitochondria started to disperse throughout the cytoplasm of the zygotes, and this dispersive distribution pattern continued until the zygotes entered the mitotic phase. At early prophase, the mitochondria redistributed from dispersive to densely accumulated around the nucleus, and during the metaphase and anaphase, the mitochondria were depleted from possible mitotic spindle region. Thereafter, during cell plate formation between daughter nuclei, the mitochondria distributed along the phragmoplast, where the new cell wall was formed. Finally, relatively equivalent amounts of mitochondria were detected in the apical and basal cells which were produced through asymmetric division of the zygotes. Further observation by treating the egg cell with latrunculin B revealed that the accumulation of mitochondria around the nuclear periphery in egg cells and early zygotes depended on the actin meshwork converging toward the egg or zygote nucleus.
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Affiliation(s)
- Hanifah Aini
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo, 192-0397, Japan
| | - Yoshikatsu Sato
- Graduate School of Science, Nagoya University, Chikusa, Nagoya, 464-8601, Japan
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Chikusa, Nagoya, 464-8601, Japan
| | - Kakishi Uno
- Graduate School of Science, Nagoya University, Chikusa, Nagoya, 464-8601, Japan
- Department of NanoBiophotonics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Tetsuya Higashiyama
- Graduate School of Science, Nagoya University, Chikusa, Nagoya, 464-8601, Japan
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Chikusa, Nagoya, 464-8601, Japan
- Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo, Tokyo, 113-0033, Japan
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo, 192-0397, Japan.
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Maryenti T, Kato N, Ichikawa M, Okamoto T. In Vitro Fertilization System Using Wheat Gametes by Electric Fusion. Methods Mol Biol 2022; 2484:259-273. [PMID: 35461457 DOI: 10.1007/978-1-0716-2253-7_18] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
In vitro fertilization (IVF) systems using isolated gametes have been used to dissect post-fertilization events in angiosperms, as female plant gametophytes are deeply embedded within the ovaries. In addition, hybrid and polyploid zygotes can be produced by using IVF systems. Complete IVF systems of maize and rice, two out of three major energy-providing crops, have been established in order to acquire detailed knowledge of mechanisms of fertilization and early embryogenesis. Following in the footsteps of previous success, a wheat IVF system was developed to introduce the advantages of this technology to wheat research. Fusion of gametes was performed via a modified electrofusion method, and the zygote formed a cell wall and two nucleoli. The zygotes divided into symmetric two-celled embryos, globular-like embryos and multicellular club-shaped embryos which are mostly consistent with those in the embryos in planta. IVF-produced club-shaped embryos developed into compact embryonic calli and subsequently regenerated into fertile plants. In this chapter, we provide a detailed description of wheat IVF system that might become an important technique for generating new genotypes of wheat and/or new hybrids as well as for investigating fertilization-induced events in wheat.
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Affiliation(s)
- Tety Maryenti
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
| | - Norio Kato
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
| | - Masako Ichikawa
- Agri-Bio Research Center, KANEKA Corp., Iwata, Shizuoka, Japan
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, Japan.
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Sharma V, Clark AJ, Kawashima T. Insights into the molecular evolution of fertilization mechanism in land plants. PLANT REPRODUCTION 2021; 34:353-364. [PMID: 34061252 DOI: 10.1007/s00497-021-00414-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2021] [Accepted: 05/14/2021] [Indexed: 05/27/2023]
Abstract
Comparative genetics and genomics among green plants, including algae, provide deep insights into the evolution of land plant sexual reproduction. Land plants have evolved successive changes during their conquest of the land and innovations in sexual reproduction have played a major role in their terrestrialization. Recent years have seen many revealing dissections of the molecular mechanisms of sexual reproduction and much new genomics data from the land plant lineage, including early diverging land plants, as well as algae. This new knowledge is being integrated to further understand how sexual reproduction in land plants evolved, identifying highly conserved factors and pathways, but also molecular changes that underpinned the emergence of new modes of sexual reproduction. Here, we review recent advances in the knowledge of land plant sexual reproduction from an evolutionary perspective and also revisit the evolution of angiosperm double fertilization.
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Affiliation(s)
- Vijyesh Sharma
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, 40546, USA
| | - Anthony J Clark
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, 40546, USA
| | - Tomokazu Kawashima
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, 40546, USA.
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Maryenti T, Ishii T, Okamoto T. Development and regeneration of wheat-rice hybrid zygotes produced by in vitro fertilization system. THE NEW PHYTOLOGIST 2021; 232:2369-2383. [PMID: 34545570 PMCID: PMC9293317 DOI: 10.1111/nph.17747] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 09/14/2021] [Indexed: 05/20/2023]
Abstract
Hybridization plays a decisive role in the evolution and diversification of angiosperms. However, the mechanisms of wide hybridization remain open because pre- and post-fertilization barriers limit the production and development of inter-subfamily/intergeneric zygotes, respectively. We examined hybridization between wheat and rice using an in vitro fertilization (IVF) system to bypass these barriers. Several gamete combinations of allopolyploid wheat-rice hybrid zygotes were successfully produced, and the developmental profiles of hybrid zygotes were analyzed. Hybrid zygotes derived from one rice egg cell and one wheat sperm cell ceased at the multicellular embryo-like structure stage. This developmental barrier was overcome by adding one wheat egg cell to the wheat-rice hybrid zygote. In the reciprocal combination, one wheat egg and one rice sperm cell, the resulting hybrid zygotes failed to divide. However, doubling the dosage of rice sperm cell allowed the hybrid zygotes to develop into plantlets. Rice chromosomes appeared to be progressively eliminated during the early developmental stage of these hybrid embryos, and c. 20% of regenerated plants showed abnormal morphology. These results suggest that hybrid breakdown can be overcome through optimization of gamete combinations, and the present hybrid will provide a new horizon for utilization of inter-subfamily genetic resources.
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Affiliation(s)
- Tety Maryenti
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawa 1‐1Hachioji, Tokyo192‐0397Japan
| | - Takayoshi Ishii
- Arid Land Research Center (ALRC)Tottori University1390 HamasakaTottori680‐0001Japan
| | - Takashi Okamoto
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawa 1‐1Hachioji, Tokyo192‐0397Japan
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Rattanawong K, Koiso N, Toda E, Kinoshita A, Tanaka M, Tsuji H, Okamoto T. Regulatory functions of ROS dynamics via glutathione metabolism and glutathione peroxidase activity in developing rice zygote. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 108:1097-1115. [PMID: 34538012 PMCID: PMC9293154 DOI: 10.1111/tpj.15497] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 08/24/2021] [Accepted: 08/25/2021] [Indexed: 06/01/2023]
Abstract
Reactive oxygen species (ROS) play essential roles in plant development and environmental stress responses. In this study, ROS dynamics, the glutathione redox status, the expression and subcellular localization of glutathione peroxidases (GPXs), and the effects of inhibitors of ROS-mediated metabolism were investigated along with fertilization and early zygotic embryogenesis in rice (Oryza sativa). Zygotes and early embryos exhibited developmental arrest upon inhibition of ROS production. Egg cells accumulated high ROS levels, and, after fertilization, intracellular ROS levels progressively declined in zygotes in which de novo expression of GPX1 and 3 was observed through upregulation of the genes. In addition to inhibition of GPX activity, depletion of glutathione impeded early embryonic development and led to failure of the zygote to appropriately decrease H2 O2 levels. Moreover, through monitoring of the glutathione redox status, the developing zygotes exhibited a progressive glutathione oxidation, which became extremely delayed under inhibited GPX activity. Our results provide insights into the importance of ROS dynamics, GPX antioxidant activity, and glutathione redox metabolism during zygotic/embryonic development.
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Affiliation(s)
- Kasidit Rattanawong
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawaHachioji, TokyoJapan
| | - Narumi Koiso
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawaHachioji, TokyoJapan
| | - Erika Toda
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawaHachioji, TokyoJapan
| | - Atsuko Kinoshita
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawaHachioji, TokyoJapan
| | - Mari Tanaka
- Kihara Institute for Biological ResearchYokohama City UniversityMaiokachoTotsuka‐kuYokohamaKanagawaJapan
| | - Hiroyuki Tsuji
- Kihara Institute for Biological ResearchYokohama City UniversityMaiokachoTotsuka‐kuYokohamaKanagawaJapan
| | - Takashi Okamoto
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawaHachioji, TokyoJapan
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14
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Ali MF, Kawashima T. Formins control dynamics of F-actin in the central cell of Arabidopsis thaliana. PLANT SIGNALING & BEHAVIOR 2021; 16:1920192. [PMID: 33944667 PMCID: PMC8244771 DOI: 10.1080/15592324.2021.1920192] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 04/16/2021] [Accepted: 04/18/2021] [Indexed: 05/28/2023]
Abstract
In the female gamete of flowering plants, sperm nuclear migration is controlled by a constant inward movement of actin filaments (F-actin) for successful fertilization. This dynamic F-actin movement is ARP2/3-independent, raising the question of how actin nucleation and polymerization is controlled in the female gamete. Using confocal microscopy live-cell imaging in combination with a pharmacological approach, we assessed the involvement of another group of actin nucleators, formins, in F-actin inward movement in the central cell of Arabidopsis thaliana. We identify that the inhibition of the formin function, by formin inhibitor SMIFH2, significantly reduced the dynamic inward movement of F-actin in the central cell, indicating that formins play a major role in actin nucleation required for F-actin inward movement in the central cell.
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Affiliation(s)
- Mohammad Foteh Ali
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, USA
| | - Tomokazu Kawashima
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, USA
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15
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Deushi R, Toda E, Koshimizu S, Yano K, Okamoto T. Effect of Paternal Genome Excess on the Developmental and Gene Expression Profiles of Polyspermic Zygotes in Rice. PLANTS (BASEL, SWITZERLAND) 2021; 10:255. [PMID: 33525652 PMCID: PMC7911625 DOI: 10.3390/plants10020255] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 01/22/2021] [Accepted: 01/26/2021] [Indexed: 11/17/2022]
Abstract
Polyploid zygotes with a paternal gamete/genome excess exhibit arrested development, whereas polyploid zygotes with a maternal excess develop normally. These observations indicate that paternal and maternal genomes synergistically influence zygote development via distinct functions. In this study, to clarify how paternal genome excess affects zygotic development, the developmental and gene expression profiles of polyspermic rice zygotes were analyzed. The results indicated that polyspermic zygotes were mostly arrested at the one-cell stage after karyogamy had completed. Through comparison of transcriptomes between polyspermic zygotes and diploid zygotes, 36 and 43 genes with up-regulated and down-regulated expression levels, respectively, were identified in the polyspermic zygotes relative to the corresponding expression in the diploid zygotes. Notably, OsASGR-BBML1, which encodes an AP2 transcription factor possibly involved in initiating rice zygote development, was expressed at a much lower level in the polyspermic zygotes than in the diploid zygotes.
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Affiliation(s)
- Ryouya Deushi
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0392, Japan; (R.D.); (E.T.)
| | - Erika Toda
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0392, Japan; (R.D.); (E.T.)
| | - Shizuka Koshimizu
- Department of Life Sciences, Meiji University, Kanagawa 214-8571, Japan; (S.K.); (K.Y.)
| | - Kentaro Yano
- Department of Life Sciences, Meiji University, Kanagawa 214-8571, Japan; (S.K.); (K.Y.)
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0392, Japan; (R.D.); (E.T.)
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16
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Armenta-Medina A, Gillmor CS, Gao P, Mora-Macias J, Kochian LV, Xiang D, Datla R. Developmental and genomic architecture of plant embryogenesis: from model plant to crops. PLANT COMMUNICATIONS 2021; 2:100136. [PMID: 33511346 PMCID: PMC7816075 DOI: 10.1016/j.xplc.2020.100136] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 12/05/2020] [Accepted: 12/11/2020] [Indexed: 05/08/2023]
Abstract
Embryonic development represents an important reproductive phase of sexually reproducing plant species. The fusion of egg and sperm produces the plant zygote, a totipotent cell that, through cell division and cell identity specification in early embryogenesis, establishes the major cell lineages and tissues of the adult plant. The subsequent morphogenesis phase produces the full-sized embryo, while the late embryogenesis maturation process prepares the seed for dormancy and subsequent germination, ensuring continuation of the plant life cycle. In this review on embryogenesis, we compare the model eudicot Arabidopsis thaliana with monocot crops, focusing on genome activation, paternal and maternal regulation of early zygote development, and key organizers of patterning, such as auxin and WOX transcription factors. While the early stages of embryo development are apparently conserved among plant species, embryo maturation programs have diversified between eudicots and monocots. This diversification in crop species reflects the likely effects of domestication on seed quality traits that are determined during embryo maturation, and also assures seed germination in different environmental conditions. This review describes the most important features of embryonic development in plants, and the scope and applications of genomics in plant embryo studies.
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Affiliation(s)
- Alma Armenta-Medina
- Global Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8, Canada
- Laboratorio Nacional de Genómica para la Biodiversidad (Langebio), Unidad de Genómica Avanzada, Centro de Investigación y Estudios Avanzados del IPN (CINVESTAV-IPN), Irapuato, Guanajuato, México
| | - C. Stewart Gillmor
- Laboratorio Nacional de Genómica para la Biodiversidad (Langebio), Unidad de Genómica Avanzada, Centro de Investigación y Estudios Avanzados del IPN (CINVESTAV-IPN), Irapuato, Guanajuato, México
| | - Peng Gao
- Global Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8, Canada
| | - Javier Mora-Macias
- Global Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8, Canada
| | - Leon V. Kochian
- Global Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8, Canada
| | - Daoquan Xiang
- National Research Council Canada, 110 Gymnasium Place, Saskatoon, SK S7N 0W9, Canada
| | - Raju Datla
- Global Institute for Food Security, University of Saskatchewan, Saskatoon, SK S7N 4J8, Canada
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17
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González-Gutiérrez AG, Gutiérrez-Mora A, Verdín J, Rodríguez-Garay B. An F-Actin Mega-Cable Is Associated With the Migration of the Sperm Nucleus During the Fertilization of the Polarity-Inverted Central Cell of Agave inaequidens. FRONTIERS IN PLANT SCIENCE 2021; 12:774098. [PMID: 34899803 PMCID: PMC8652256 DOI: 10.3389/fpls.2021.774098] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 11/01/2021] [Indexed: 05/15/2023]
Abstract
Asparagaceae's large embryo sacs display a central cell nucleus polarized toward the chalaza, which means the sperm nucleus that fuses with it during double fertilization migrates an atypical long distance before karyogamy. Because of the size and inverted polarity of the central cell in Asparagaceae, we hypothesize that the second fertilization process is supported by an F-actin machinery different from the short-range F-actin structures observed in Arabidopsis and other plant models. Here, we analyzed the F-actin dynamics of Agave inaequidens, a classical Asparagaceae, before, during, and after the central cell fertilization. Several parallel F-actin cables, spanning from the central cell nucleus to the micropylar pole, and enclosing the vacuole, were observed. As fertilization progressed, a thick F-actin mega-cable traversing the vacuole appeared, connecting the central cell nucleus with the micropylar pole near the egg cell. This mega-cable wrapped the sperm nucleus in transit to fuse with the central cell nucleus. Once karyogamy finished, and the endosperm started to develop, the mega-cable disassembled, but new F-actin structures formed. These observations suggest that Asparagaceae, and probably other plant species with similar embryo sacs, evolved an F-actin machinery specifically adapted to support the migration of the fertilizing sperm nucleus within a large-sized and polarity-inverted central cell.
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Affiliation(s)
- Alejandra G. González-Gutiérrez
- Unidad de Biotecnología Vegetal, CIATEJ, Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco, A.C., Zapopan, Mexico
| | - Antonia Gutiérrez-Mora
- Unidad de Biotecnología Vegetal, CIATEJ, Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco, A.C., Zapopan, Mexico
| | - Jorge Verdín
- Unidad de Biotecnología Industrial, CIATEJ, Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco, A.C., Zapopan, Mexico
- *Correspondence: Jorge Verdín,
| | - Benjamín Rodríguez-Garay
- Unidad de Biotecnología Vegetal, CIATEJ, Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco, A.C., Zapopan, Mexico
- Benjamín Rodríguez-Garay,
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18
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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: 16] [Impact Index Per Article: 4.0] [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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19
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Shin JM, Yuan L, Ohme-Takagi M, Kawashima T. Cellular dynamics of double fertilization and early embryogenesis in flowering plants. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2020; 336:642-651. [PMID: 32638525 DOI: 10.1002/jez.b.22981] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Revised: 06/12/2020] [Accepted: 06/18/2020] [Indexed: 12/12/2022]
Abstract
Flowering plants (angiosperms) perform a unique double fertilization in which two sperm cells fuse with two female gamete cells in the embryo sac to develop a seed. Furthermore, during land plant evolution, the mode of sexual reproduction has been modified dramatically from motile sperm in the early-diverging land plants, such as mosses and ferns as well as some gymnosperms (Ginkgo and cycads) to nonmotile sperm that are delivered to female gametes by the pollen tube in flowering plants. Recent studies have revealed the cellular dynamics and molecular mechanisms for the complex series of double fertilization processes and elucidated differences and similarities between animals and plants. Here, together with a brief comparison with animals, we review the current understanding of flowering plant zygote dynamics, covering from gamete nuclear migration, karyogamy, and polyspermy block, to zygotic genome activation as well as asymmetrical division of the zygote. Further analyses of the detailed molecular and cellular mechanisms of flowering plant fertilization should shed light on the evolution of the unique sexual reproduction of flowering plants.
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Affiliation(s)
- Ji Min Shin
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky.,Kentucky Tobacco Research and Development Center, University of Kentucky, Lexington, Kentucky.,Graduate School of Science and Engineering, Saitama University, Saitama, Saitama, Japan
| | - Ling Yuan
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky.,Kentucky Tobacco Research and Development Center, University of Kentucky, Lexington, Kentucky
| | - Masaru Ohme-Takagi
- Graduate School of Science and Engineering, Saitama University, Saitama, Saitama, Japan.,Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan
| | - Tomokazu Kawashima
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, Kentucky
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20
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Ohnishi Y, Kawashima T. Plasmogamic Paternal Contributions to Early Zygotic Development in Flowering Plants. FRONTIERS IN PLANT SCIENCE 2020; 11:871. [PMID: 32636867 PMCID: PMC7317025 DOI: 10.3389/fpls.2020.00871] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 05/28/2020] [Indexed: 06/01/2023]
Abstract
Flowering plant zygotes possess complete developmental potency, and the mixture of male and female genetic and cytosolic materials in the zygote is a trigger to initiate embryo development. Plasmogamy, the fusion of the gamete cytoplasms, facilitates the cellular dynamics of the zygote. In the last decade, mutant analyses, live cell imaging-based observations, and direct observations of fertilized egg cells by in vitro fusion of isolated gametes have accelerated our understanding of the post-plasmogamic events in flowering plants including cell wall formation, gamete nuclear migration and fusion, and zygotic cell elongation and asymmetric division. Especially, it has become more evident that paternal parent-of-origin effects, via sperm cytoplasm contents, not only control canonical early zygotic development, but also activate a biparental signaling pathway critical for cell fate determination after the first cell division. Here, we summarize the plasmogamic paternal contributions via the entry of sperm contents during/after fertilization in flowering plants.
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Affiliation(s)
- Yukinosuke Ohnishi
- Kihara Institute for Biological Research, Yokohama City University, Yokohama, Japan
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, United States
| | - Tomokazu Kawashima
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, United States
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21
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Kono M, Kawaguchi H, Mizusawa N, Yamori W, Suzuki Y, Terashima I. Far-Red Light Accelerates Photosynthesis in the Low-Light Phases of Fluctuating Light. PLANT & CELL PHYSIOLOGY 2020; 61:1-2. [PMID: 31617558 DOI: 10.1093/pcp/pcz211] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 11/04/2019] [Indexed: 05/27/2023]
Abstract
It is well known that far-red light (FR; >700 nm) drives PSI photochemistry, but its effect on photosynthetic performance has received little attention. In this study, the effects of the addition of FR to red fluctuating light (FL) have on photosynthesis were examined in the leaves of Arabidopsis thaliana. Light-activated leaves were illuminated with FL [alternating high light/low light (HL/LL) at 800/30 μmol m-2 s-1] for 10-15 min without or with FR at intensities that reflected natural conditions. The CO2 assimilation rates upon the transition from HL to LL were significantly greater with FR than without FR. The enhancement of photosynthesis by FR was small under the steady-state conditions and in the HL phases of FL. Proton conductivity through the thylakoid membrane (gH+) in the LL phases of FL, estimated from the dark relaxation kinetics of the electrochromic absorbance shift, was greater with FR than without FR. The relaxation of non-photochemical quenching (NPQ) in the PSII antenna system and the increase in PSII photochemistry in the LL phases accelerated in the presence of FR. Similar FR-effects in FL were confirmed in typical sun and shade plants. On the basis of these results, we concluded that FR exerted beneficial effects on photosynthesis in FL by exciting PSI and accelerating NPQ relaxation and PSII-yield increase. This was probably because of the increased gH+, which would reflect faster ΔpH dissipation and ATP synthesis.
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Affiliation(s)
- Masaru Kono
- Department of Biological Sciences, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
| | - Hikaru Kawaguchi
- Faculty of Science, Kanagawa University, 2946 Tsuchiya, Hiratsuka, Kanagawa, 259-1293 Japan
| | - Naoki Mizusawa
- Department of Frontier Bioscience, Hosei University, Koganei, Tokyo, 184-8584 Japan
- Research Center for Micro-Nano Technology, Hosei University, Koganei, Tokyo, 184-0003 Japan
| | - Wataru Yamori
- Department of Biological Sciences, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
| | - Yoshihiro Suzuki
- Faculty of Science, Kanagawa University, 2946 Tsuchiya, Hiratsuka, Kanagawa, 259-1293 Japan
| | - Ichiro Terashima
- Department of Biological Sciences, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan
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22
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Maruyama D, Higashiyama T, Endo T, Nishikawa SI. Fertilization-Coupled Sperm Nuclear Fusion Is Required for Normal Endosperm Nuclear Proliferation. PLANT & CELL PHYSIOLOGY 2020; 61:29-40. [PMID: 31410484 DOI: 10.1093/pcp/pcz158] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2019] [Accepted: 08/07/2019] [Indexed: 05/13/2023]
Abstract
Angiosperms exhibit double fertilization, a process in which one of the sperm cells released from the pollen tube fertilizes the egg, while the other sperm cell fertilizes the central cell, giving rise to the embryo and endosperm, respectively. We have previously reported two polar nuclear fusion-defective double knockout mutants of Arabidopsis thaliana immunoglobulin binding protein (BiP), a molecular chaperone of the heat shock protein 70 (Hsp70) localized in the endoplasmic reticulum (ER), (bip1 bip2) and its partner ER-resident J-proteins, ERdj3A and P58IPK (erdj3a p58ipk). These mutants are defective in the fusion of outer nuclear membrane and exhibit characteristic seed developmental defects after fertilization with wild-type pollen, which are accompanied by aberrant endosperm nuclear proliferation. In this study, we used time-lapse live-cell imaging analysis to determine the cause of aberrant endosperm nuclear division in these mutant seeds. We found that the central cell of bip1 bip2 or erdj3a p58ipk double mutant female gametophytes was also defective in sperm nuclear fusion at fertilization. Sperm nuclear fusion was achieved after the onset of the first endosperm nuclear division. However, division of the condensed sperm nucleus resulted in aberrant endosperm nuclear divisions and delayed expression of paternally derived genes. By contrast, the other double knockout mutant, erdj3b p58ipk, which is defective in the fusion of inner membrane of polar nuclei but does not show aberrant endosperm nuclear proliferation, was not defective in sperm nuclear fusion at fertilization. We thus propose that premitotic sperm nuclear fusion in the central cell is critical for normal endosperm nuclear proliferation.
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Affiliation(s)
- Daisuke Maruyama
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602 Japan
- Kihara Institute for Biological Research, Yokohama City University, 641-12 Maioka-cho, Totsuka-ku, Yokohama, 244-0813 Japan
| | - Tetsuya Higashiyama
- Division of Biological Science, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602 Japan
- WPI-Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601 Japan
| | - Toshiya Endo
- Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, 464-8602 Japan
- Faculty of Life Sciences, Kyoto Sangyo University, Kamigamo-motoyama, Kita-ku, Kyoto, 603-8555 Japan
| | - Shuh-Ichi Nishikawa
- Department of Biology, Faculty of Science, Niigata University, 8050 Ikarashi 2-no-cho, Nishi-ku, Niigata, 950-2181 Japan
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23
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Abstract
In angiosperms, fertilization and embryogenesis occur in the embryo sac, which is deeply embedded in ovular tissue. In vitro fertilization (IVF) systems using isolated gametes have been utilized to dissect postfertilization events in angiosperms, such as egg activation, zygotic development, and early embryogenesis. In addition, using IVF systems, interspecific zygotes and polyploid zygotes have been artificially produced, and their developmental profiles/mechanisms have been analyzed. Taken together, the IVF system can be considered a powerful technique for investigating the fertilization-induced developmental sequences in zygotes and generating new cultivars with desirable characteristics. Here, we describe the procedures for the isolation of rice gametes, electrofusion of gametes, and the culture of the produced zygotes and embryo.
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Affiliation(s)
- Md Hassanur Rahman
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Erika Toda
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan.
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24
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Kao P, Nodine MD. Transcriptional Activation of Arabidopsis Zygotes Is Required for Initial Cell Divisions. Sci Rep 2019; 9:17159. [PMID: 31748673 PMCID: PMC6868190 DOI: 10.1038/s41598-019-53704-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 11/04/2019] [Indexed: 11/10/2022] Open
Abstract
Commonly referred to as the maternal-to-zygotic transition, the shift of developmental control from maternal-to-zygotic genomes is a key event during animal and plant embryogenesis. Together with the degradation of parental gene products, the increased transcriptional activities of the zygotic genome remodels the early embryonic transcriptome during this transition. Although evidence from multiple flowering plants suggests that zygotes become transcriptionally active soon after fertilization, the timing and developmental requirements of zygotic genome activation in Arabidopsis thaliana (Arabidopsis) remained a matter of debate until recently. In this report, we optimized an expansion microscopy technique for robust immunostaining of Arabidopsis ovules and seeds. This enabled the detection of marks indicative of active transcription in zygotes before the first cell division. Moreover, we employed a live-imaging culture system together with transcriptional inhibitors to demonstrate that such active transcription is physiologically required in zygotes and early embryos. Our results indicate that zygotic genome activation occurs soon after fertilization and is required for the initial zygotic divisions in Arabidopsis.
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Affiliation(s)
- Ping Kao
- Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, 1030, Vienna, Austria
| | - Michael D Nodine
- Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, 1030, Vienna, Austria.
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25
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Toda E, Okamoto T. Polyspermy in angiosperms: Its contribution to polyploid formation and speciation. Mol Reprod Dev 2019; 87:374-379. [PMID: 31736192 DOI: 10.1002/mrd.23295] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Accepted: 10/28/2019] [Indexed: 12/14/2022]
Abstract
Polyploidization has played a major role in the long-term diversification and evolutionary success of angiosperms. Triploid formation among diploid plants, which is generally considered to be achieved by fertilization of an unreduced gamete with a reduced one, has been accepted as a means of polyploid production. In addition, it has been supposed that polyspermy also contributes to the triploid formation in maize, wheat, and some orchids; however, such a mechanism has been considered uncommon because reproducing the polyspermic situation and unambiguously investigating developmental profiles of polyspermic zygotes are difficult. To overcome these problems, rice polyspermic zygotes have been successfully produced by electrofusion of an egg cell with two sperm cells, and their developmental profiles have been monitored. The triploid zygotes progress through karyogamy and divide into two-celled embryos via a typical bipolar mitotic division; the two-celled embryos further develop into triploid plants, indicating that polyspermic plant zygotes, unlike those of animals, can develop normally. Furthermore, progenies consisting of triparental genetic materials have been successfully obtained in Arabidopsis through the pollination of two different kinds of male parents with a female parent. These different pieces of evidence for development and emergence of polyspermic zygotes in vitro and in planta suggest that polyspermy is a key event in polyploidization and species diversification.
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Affiliation(s)
- Erika Toda
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
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26
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Ohnishi Y, Kokubu I, Kinoshita T, Okamoto T. Sperm Entry into the Egg Cell Induces the Progression of Karyogamy in Rice Zygotes. PLANT & CELL PHYSIOLOGY 2019; 60:1656-1665. [PMID: 31076767 DOI: 10.1093/pcp/pcz077] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 04/16/2019] [Indexed: 05/11/2023]
Abstract
Karyogamy is a prerequisite event for plant embryogenesis, in which dynamic changes in nuclear architecture and the establishment of appropriate gene expression patterns must occur. However, the precise role of the male and female gametes in the progression of karyogamy still remains elusive. Here, we show that the sperm cell possesses the unique property to drive steady and swift nuclear fusion. When we fertilized egg cells with sperm cells in vitro, the immediate fusion of the male and female nuclei in the zygote progressed. This rapid nuclear fusion did not occur when two egg cells were artificially fused. However, the nuclear fusion of two egg nuclei could be accelerated by additional sperm entry or the exogenous application of calcium, suggesting that possible increase of cytosolic Ca2+ level via sperm entry into the egg cell efficiently can facilitate karyogamy. In contrast to zygotes, the egg-egg fusion cells failed to proliferate beyond an early developmental stage. Our transcriptional analyses also revealed the rapid activation of zygotic genes in zygotes, whereas there was no expression in fused cells without the male contribution. Thus, the male sperm cell has the ability to cause immediate karyogamy and to establish appropriate gene expression patterns in the zygote.
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Affiliation(s)
- Yukinosuke Ohnishi
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa 1-1, Hachioji, Tokyo, Japan
- Kihara Institute for Biological Research, Yokohama City University, Maioka 641-12, Totsuka, Yokohama, Kanagawa, Japan
| | - Iwao Kokubu
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa 1-1, Hachioji, Tokyo, Japan
| | - Tetsu Kinoshita
- Kihara Institute for Biological Research, Yokohama City University, Maioka 641-12, Totsuka, Yokohama, Kanagawa, Japan
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa 1-1, Hachioji, Tokyo, Japan
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Maryenti T, Kato N, Ichikawa M, Okamoto T. Establishment of an In Vitro Fertilization System in Wheat (Triticum aestivum L.). PLANT & CELL PHYSIOLOGY 2019; 60:835-843. [PMID: 30605551 DOI: 10.1093/pcp/pcy250] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Accepted: 12/21/2018] [Indexed: 05/11/2023]
Abstract
In vitro fertilization (IVF) systems using isolated gametes have been utilized to dissect post-fertilization events in angiosperms, since the female gametophytes of plants are deeply embedded within ovaries. In addition, IVF systems have been used to produce hybrid and polyploid zygotes. Complete IVF systems have been established in maize and rice, two of three major crop species providing the majority of human energy intake. Among those crop species, gametes of wheat have not been used to establish a complete IVF system successfully. In this study, a wheat IVF system was developed to introduce the advantages of this technology to wheat research. Fusion of gametes was performed via a modified electrofusion method, and the fusion product, a zygote, formed a cell wall and two nucleoli. The first division of zygotes was observed 19-27 h after fusion, and the resulting two-celled embryo developed into 10-20-celled globular-like embryos and multicellular club-shaped embryos by 3 and 7-10 d after fusion, respectively. Such zygotic division profiles were mostly consistent with those in the embryo sac, suggesting that the division profile of IVF-produced early embryos reflects that of early embryos in planta. Although the IVF-produced club-shaped embryos did not develop into differentiated embryos but into compact embryonic calli, fertile plants could be regenerated from the embryonic calli, and the seeds harvested from those plants grew normally into seedlings. The IVF system described here might become an important technique for generating new genotypes of wheat and/or new hybrids as well as for investigating fertilization-induced events in wheat.
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Affiliation(s)
- Tety Maryenti
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa 1-1, Hachioji, Tokyo, Japan
| | - Norio Kato
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa 1-1, Hachioji, Tokyo, Japan
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Tsurumi, Yokohama, Japan
- Plant Innovation Center, Japan Tobacco Inc., Higashihara 700, Iwata, Shizuoka, Japan
| | - Masako Ichikawa
- Plant Innovation Center, Japan Tobacco Inc., Higashihara 700, Iwata, Shizuoka, Japan
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa 1-1, Hachioji, Tokyo, Japan
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Tsurumi, Yokohama, Japan
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Rahman MH, Toda E, Kobayashi M, Kudo T, Koshimizu S, Takahara M, Iwami M, Watanabe Y, Sekimoto H, Yano K, Okamoto T. Expression of Genes from Paternal Alleles in Rice Zygotes and Involvement of OsASGR-BBML1 in Initiation of Zygotic Development. PLANT & CELL PHYSIOLOGY 2019; 60:725-737. [PMID: 30801122 DOI: 10.1093/pcp/pcz030] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Accepted: 02/07/2019] [Indexed: 05/11/2023]
Abstract
Upon fertilization in angiosperms, one sperm cell fuses with the egg cell to produce a zygote, and, via karyogamy, the parental genetic information is combined to form the diploid zygotic genome. Recently, analyses with parentally imbalanced rice zygotes indicated that parental genomes are utilized synergistically in zygotes with different functions, and that genes transcribed from the paternal or maternal allele might play important roles in zygotic development. Herein, we first conducted single nucleotide polymorphism-based mRNA-sequencing using intersubspecific rice zygotes. Twenty-three genes, with paternal allele-specific expression in zygotes, were identified, and, surprisingly, their allele dependencies in the globular-like embryo tended to be biallelic. This suggests that the paternal-dependent expression of these genes is temporary, occurring during the early stages of zygote development. Of the 23 genes, we focused on Oryza sativa Apospory-specific Genome Region (ASGR)-BABY-BOOM LIKE (BBML) 1 (OsASGR-BBML1), presumed to encode an AP2-transcription factor, due to its reported role in zygotic development. Interestingly, ectopic expression of OsASGR-BBML1 in egg cells induced nuclear and cell divisions, indicating that exogenously expressed OsASGR-BBML1 converts the proliferation status of the egg cell from quiescent to active. In addition, the suppression of the function of OsASGR-BBML1 and its homologs in zygotes resulted in the developmental arrest, suggesting that OsASGR-BBML1 possesses an important role in initiating zygotic development. Monoallelic or preferential gene expression from the paternal genome in the zygote might be a safety mechanism allowing egg cells to suppress the gene expression cascade toward early embryogenesis that is normally triggered by fusion with a sperm cell.
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Affiliation(s)
- Md Hassanur Rahman
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Erika Toda
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | | | - Toru Kudo
- Department of Life Sciences, Meiji University, Kanagawa, Japan
| | | | - Mirei Takahara
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Momoka Iwami
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Yoriko Watanabe
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
| | - Hiroyuki Sekimoto
- Department of Chemical and Biological Sciences, Japan Women's University, Tokyo, Japan
| | - Kentaro Yano
- Department of Life Sciences, Meiji University, Kanagawa, Japan
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan
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29
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Wang Y. Engineering stable heterosis. J Genet Genomics 2019; 46:1-3. [DOI: 10.1016/j.jgg.2019.01.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 01/09/2019] [Indexed: 12/27/2022]
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Fatema U, Ali MF, Hu Z, Clark AJ, Kawashima T. Gamete Nuclear Migration in Animals and Plants. FRONTIERS IN PLANT SCIENCE 2019; 10:517. [PMID: 31068960 PMCID: PMC6491811 DOI: 10.3389/fpls.2019.00517] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 04/03/2019] [Indexed: 05/04/2023]
Abstract
The migration of male and female gamete nuclei to each other in the fertilized egg is a prerequisite for the blending of genetic materials and the initiation of the next generation. Interestingly, many differences have been found in the mechanism of gamete nuclear movement among animals and plants. Female to male gamete nuclear movement in animals and brown algae relies on microtubules. By contrast, in flowering plants, the male gamete nucleus is carried to the female gamete nucleus by the filamentous actin cytoskeleton. As techniques have developed from light, electron, fluorescence, immunofluorescence, and confocal microscopy to live-cell time-lapse imaging using fluorescently labeled proteins, details of these differences in gamete nuclear migration have emerged in a wide range of eukaryotes. Especially, gamete nuclear migration in flowering plants such as Arabidopsis thaliana, rice, maize, and tobacco has been further investigated, and showed high conservation of the mechanism, yet, with differences among these species. Here, with an emphasis on recent developments in flowering plants, we survey gamete nuclear migration in different eukaryotic groups and highlight the differences and similarities among species.
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Affiliation(s)
- Umma Fatema
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, United States
| | - Mohammad F. Ali
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, United States
| | - Zheng Hu
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, United States
- The Key Lab of Plant Pathology of Hubei Province, Huazhong Agricultural University, Wuhan, China
| | - Anthony J. Clark
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, United States
| | - Tomokazu Kawashima
- Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, United States
- *Correspondence: Tomokazu Kawashima,
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van Nocker S. Hybrids without hybridization-can it revolutionize horticulture? HORTICULTURE RESEARCH 2018; 5:76. [PMID: 30588321 PMCID: PMC6303291 DOI: 10.1038/s41438-018-0113-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 12/17/2018] [Indexed: 06/09/2023]
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32
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Khanday I, Skinner D, Yang B, Mercier R, Sundaresan V. A male-expressed rice embryogenic trigger redirected for asexual propagation through seeds. Nature 2018; 565:91-95. [PMID: 30542157 DOI: 10.1038/s41586-018-0785-8] [Citation(s) in RCA: 208] [Impact Index Per Article: 34.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 10/29/2018] [Indexed: 11/09/2022]
Abstract
The molecular pathways that trigger the initiation of embryogenesis after fertilization in flowering plants, and prevent its occurrence without fertilization, are not well understood1. Here we show in rice (Oryza sativa) that BABY BOOM1 (BBM1), a member of the AP2 family2 of transcription factors that is expressed in sperm cells, has a key role in this process. Ectopic expression of BBM1 in the egg cell is sufficient for parthenogenesis, which indicates that a single wild-type gene can bypass the fertilization checkpoint in the female gamete. Zygotic expression of BBM1 is initially specific to the male allele but is subsequently biparental, and this is consistent with its observed auto-activation. Triple knockout of the genes BBM1, BBM2 and BBM3 causes embryo arrest and abortion, which are fully rescued by male-transmitted BBM1. These findings suggest that the requirement for fertilization in embryogenesis is mediated by male-genome transmission of pluripotency factors. When genome editing to substitute mitosis for meiosis (MiMe)3,4 is combined with the expression of BBM1 in the egg cell, clonal progeny can be obtained that retain genome-wide parental heterozygosity. The synthetic asexual-propagation trait is heritable through multiple generations of clones. Hybrid crops provide increased yields that cannot be maintained by their progeny owing to genetic segregation. This work establishes the feasibility of asexual reproduction in crops, and could enable the maintenance of hybrids clonally through seed propagation5,6.
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Affiliation(s)
- Imtiyaz Khanday
- Department of Plant Biology, University of California, Davis, CA, USA.,Innovative Genomics Institute, Berkeley, CA, USA
| | - Debra Skinner
- Department of Plant Biology, University of California, Davis, CA, USA
| | - Bing Yang
- Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, USA
| | - Raphael Mercier
- Institut Jean-Pierre Bourgin, INRA, AgroParisTech, CNRS, Université Paris-Saclay, Versailles, France
| | - Venkatesan Sundaresan
- Department of Plant Biology, University of California, Davis, CA, USA. .,Innovative Genomics Institute, Berkeley, CA, USA. .,Department of Plant Sciences, University of California, Davis, CA, USA.
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Toda E, Ohnishi Y, Okamoto T. An imbalanced parental genome ratio affects the development of rice zygotes. JOURNAL OF EXPERIMENTAL BOTANY 2018; 69:2609-2619. [PMID: 29538694 PMCID: PMC5920335 DOI: 10.1093/jxb/ery094] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 03/06/2018] [Indexed: 05/25/2023]
Abstract
Upon double fertilization, one sperm cell fuses with the egg cell to form a zygote with a 1:1 maternal-to-paternal genome ratio (1m:1p), and another sperm cell fuses with the central cell to form a triploid primary endosperm cell with a 2m:1p ratio, resulting in formation of the embryo and the endosperm, respectively. The endosperm is known to be considerably sensitive to the ratio of the parental genomes. However, the effect of an imbalance of the parental genomes on zygotic development and embryogenesis has not been well studied, because it is difficult to reproduce the parental genome-imbalanced situation in zygotes and to monitor the developmental profile of zygotes without external effects from the endosperm. In this study, we produced polyploid zygotes with an imbalanced parental genome ratio by electro-fusion of isolated rice gametes and observed their developmental profiles. Polyploid zygotes with an excess maternal gamete/genome developed normally, whereas approximately half to three-quarters of polyploid zygotes with a paternal excess showed developmental arrests. These results indicate that paternal and maternal genomes synergistically serve zygote development with distinct functions, and that genes with monoallelic expression play important roles during zygotic development and embryogenesis.
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Affiliation(s)
- Erika Toda
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo, Japan
- Plant Breeding Innovation Laboratory, RIKEN Innovation Center, Tsurumi-ku, Yokohama, Japan
| | - Yukinosuke Ohnishi
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo, Japan
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo, Japan
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Sukawa Y, Okamoto T. Cell cycle in egg cell and its progression during zygotic development in rice. PLANT REPRODUCTION 2018; 31:107-116. [PMID: 29270910 DOI: 10.1007/s00497-017-0318-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Accepted: 12/04/2017] [Indexed: 05/20/2023]
Abstract
Rice egg is arrested at G1 phase probably by OsKRP2. After fusion with sperm, karyogamy, OsWEE1-mediated parental DNA integrity in zygote nucleus, zygote progresses cell cycle to produce two-celled embryo. In angiosperms, female and male gametes exist in gametophytes after the complementation of meiosis and the progression of nuclear/cell division of the haploid cell. Within the embryo sac, the egg cell is specially differentiated for fertilization and subsequent embryogenesis, and cellular programs for embryonic development, such as restarting the cell cycle and de novo gene expression, are halted. There is only limited knowledge about how the cell cycle in egg cells restarts toward zygotic division, although the conversion of the cell cycle from a quiescent and arrested state to an active state is the most evident transition of cell status from egg cell to zygote. This is partly due to the difficulty in direct access and analysis of egg cells, zygotes and early embryos, which are deeply embedded in ovaries. In this study, precise relative DNA amounts in the nuclei of egg cells, developing zygotes and cells of early embryos were measured, and the cell cycle of a rice egg cell was estimated as the G1 phase with a 1C DNA level. In addition, increases in DNA content in zygote nuclei via karyogamy and DNA replication were also detectable according to progression of the cell cycle. In addition, expression profiles for cell cycle-related genes in egg cells and zygotes were also addressed, and it was suggested that OsKRP2 and OsWEE1 function in the inhibition of cell cycle progression in egg cells and in checkpoint of parental DNA integrity in zygote nucleus, respectively.
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Affiliation(s)
- Yumiko Sukawa
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa 1-1, Hachioji, Tokyo, 192-0397, Japan
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa 1-1, Hachioji, Tokyo, 192-0397, Japan.
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35
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36
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Okamoto T, Ohnishi Y, Toda E. Development of polyspermic zygote and possible contribution of polyspermy to polyploid formation in angiosperms. JOURNAL OF PLANT RESEARCH 2017; 130:485-490. [PMID: 28275885 DOI: 10.1007/s10265-017-0913-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 01/11/2017] [Indexed: 06/06/2023]
Abstract
Fertilization is a general feature of eukaryotic uni- and multicellular organisms to restore a diploid genome from female and male gamete haploid genomes. In angiosperms, polyploidization is a common phenomenon, and polyploidy would have played a major role in the long-term diversification and evolutionary success of plants. As for the mechanism of formation of autotetraploid plants, the triploid-bridge pathway, crossing between triploid and diploid plants, is considered as a major pathway. For the emergence of triploid plants, fusion of an unreduced gamete with a reduced gamete is generally accepted. In addition, the possibility of polyspermy has been proposed for maize, wheat and some orchids, although it has been regarded as an uncommon mechanism of triploid formation. One of the reasons why polyspermy is regarded as uncommon is because it is difficult to reproduce the polyspermy situation in zygotes and to analyze the developmental profiles of polyspermic triploid zygotes. Recently, polyspermic rice zygotes were successfully produced by electric fusion of an egg cell with two sperm cells, and their developmental profiles were monitored. Two sperm nuclei and an egg nucleus fused into a zygotic nucleus in the polyspermic zygote, and the triploid zygote divided into a two-celled embryo via mitotic division with a typical bipolar microtubule spindle. The two-celled proembryos further developed and regenerated into triploid plants. These suggest that polyspermic plant zygotes have the potential to form triploid embryos, and that polyspermy in angiosperms might be a pathway for the formation of triploid plants.
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Affiliation(s)
- Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji, Tokyo, 192-0397, Japan.
| | - Yukinosuke Ohnishi
- Department of Biological Sciences, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji, Tokyo, 192-0397, Japan
| | - Erika Toda
- Department of Biological Sciences, Tokyo Metropolitan University, 1-1 Minami-osawa, Hachioji, Tokyo, 192-0397, Japan
- Plant Breeding Innovation Laboratory, RIKEN Innovation Center, 1-7-22 Suehiro-cho, Tsurumi, Yokohama, 230-0045, Japan
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Conner JA, Podio M, Ozias-Akins P. Haploid embryo production in rice and maize induced by PsASGR-BBML transgenes. PLANT REPRODUCTION 2017; 30:41-52. [PMID: 28238020 DOI: 10.1007/s00497-017-0298-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 02/13/2017] [Indexed: 05/18/2023]
Abstract
The PsASGR - BBML transgene, derived from a wild apomictic grass species, can induce parthenogenesis, embryo formation without fertilization, in rice and maize, leading to the formation of haploid plants. The ability to engineer apomictic crop plants using genes identified from naturally occurring apomicts will depend on the ability of those genes to function in crop plants. The PsASGR-BBML transgene, derived from the apomictic species Pennisetum squamulatum, promotes parthenogenesis in sexual pearl millet, a member of the same genus, leading to the formation of haploid embryos. This study determined that the PsASGR-BBML transgene can induce haploid embryo development in two major monocot crops, maize and rice. Transgene variations tested included two different promoters and the use of both genomic and cDNA PsASGR-BBML-derived sequences. Haploid plants were recovered from mature caryopses (seed) of rice and maize lines at variable rates. The PsASGR-BBML transgenes failed to induce measurable haploid seed development in the model genetic plant system Arabidopsis thaliana. Complexity of embryo development, as documented in transgenic rice lines, identifies the need for further characterization of the PsASGR-BBML gene.
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Affiliation(s)
- Joann A Conner
- Department of Horticulture, University of Georgia, Tifton Campus, Tifton, GA, 31793, USA.
| | - Maricel Podio
- Department of Horticulture, University of Georgia, Tifton Campus, Tifton, GA, 31793, USA
| | - Peggy Ozias-Akins
- Department of Horticulture, University of Georgia, Tifton Campus, Tifton, GA, 31793, USA
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Ohnishi Y, Okamoto T. Nuclear migration during karyogamy in rice zygotes is mediated by continuous convergence of actin meshwork toward the egg nucleus. JOURNAL OF PLANT RESEARCH 2017; 130:339-348. [PMID: 27995374 DOI: 10.1007/s10265-016-0892-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 08/10/2016] [Indexed: 05/20/2023]
Abstract
Fertilization is comprised of two sequential fusion processes; plasmogamy and karyogamy. Karyogamy completes with migration and fusion of the male and female nuclei in the fused cell. In animals, microtubules organized by the centrosome control female/male pronuclei migration. In contrast, the nuclear migration in fused gametes of angiosperms is controlled by actin filaments, but the mechanism that regulates actin filament-dependent nuclear migration is not clear. In this study, we prepared fused rice (Oryza sativa L.) gametes/zygotes using in vitro fertilization and observed the spatial and temporal movements of actin filaments and sperm nuclei. Our results show that actin filaments in egg cells form a meshwork structure surrounding the nuclei. Quantitative analysis of the actin meshwork dynamics suggests that actin meshwork converges toward the egg nucleus. In egg cells fused with sperm cells, actin filaments appeared to interact with a portion of the sperm nuclear membrane. The velocity of the actin filaments was positively correlated with the velocity of the sperm nucleus during karyogamy. These results suggest that sperm nuclear membrane and actin filaments physically interact with each other during karyogamy, and that the sperm nucleus migrates toward the egg nucleus through the convergence of the actin meshwork. Interestingly, actin filament velocity increased promptly after gamete fusion and was further elevated during nuclear fusion. In addition to the migration of gamete nuclei, convergence of actin meshwork may also be critical during early zygotic developments.
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Affiliation(s)
- Yukinosuke Ohnishi
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa 1-1, Hachioji, Tokyo, 192-0397, Japan.
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa 1-1, Hachioji, Tokyo, 192-0397, Japan
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Peng X, Yan T, Sun M. The WASP-Arp2/3 complex signal cascade is involved in actin-dependent sperm nuclei migration during double fertilization in tobacco and maize. Sci Rep 2017; 7:43161. [PMID: 28225074 PMCID: PMC5320560 DOI: 10.1038/srep43161] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Accepted: 01/20/2017] [Indexed: 12/14/2022] Open
Abstract
Sperm nuclear migration during fertilization in Arabidopsis and rice has recently been found to be actin-dependent, but the driving force behind this actin cytoskeleton-dependent motion is unclear. Here, we confirmed that the actin-dependent sperm nuclei migration during fertilization is a conserved mechanism in plants. Using in vitro fertilization systems, we showed that a functional actin is also essential in maize and tobacco for sperm nuclei migration after gamete membrane fusion. Cytoskeleton depolymerization inhibitor treatments supported the view that sperm nuclei migration is actin-dependent but microtubule-independent in both egg cell and central cell during double fertilization. We further revealed that the actin-based motor myosin is not the driving force for sperm nuclear migration in maize and tobacco. The WASP-Arp2/3 complex signal cascade is shown here to be involved in the regulation of sperm nuclear migration in maize and tobacco. It is interesting that sperm nuclei migration within somatic cell also need WASP-Arp2/3 complex signal cascade and actin, suggesting that the mechanism of sperm nuclear migration is not gamete specific.
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Affiliation(s)
- Xiongbo Peng
- State Key Laboratory for Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Tingting Yan
- State Key Laboratory for Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Mengxiang Sun
- State Key Laboratory for Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
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40
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Abstract
Compared with the animal kingdom, fertilization is particularly complex in flowering plants (angiosperms). Sperm cells of angiosperms have lost their motility and require transportation as a passive cargo by the pollen tube cell to the egg apparatus (egg cell and accessory synergid cells). Sperm cell release from the pollen tube occurs after intensive communication between the pollen tube cell and the receptive synergid, culminating in the lysis of both interaction partners. Following release of the two sperm cells, they interact and fuse with two dimorphic female gametes (the egg and the central cell) forming the major seed components embryo and endosperm, respectively. This process is known as double fertilization. Here, we review the current understanding of the processes of sperm cell reception, gamete interaction, their pre-fertilization activation and fusion, as well as the mechanisms plants use to prevent the fusion of egg cells with multiple sperm cells. The role of Ca(2+) is highlighted in these various processes and comparisons are drawn between fertilization mechanisms in flowering plants and other eukaryotes, including mammals.
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Affiliation(s)
- Thomas Dresselhaus
- Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, 93040 Regensburg, Germany.
| | - Stefanie Sprunck
- Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, 93040 Regensburg, Germany
| | - Gary M Wessel
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912, USA
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Toda E, Okamoto T. Formation of triploid plants via possible polyspermy. PLANT SIGNALING & BEHAVIOR 2016; 11:e1218107. [PMID: 27617495 PMCID: PMC5058460 DOI: 10.1080/15592324.2016.1218107] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 07/20/2016] [Accepted: 07/22/2016] [Indexed: 05/28/2023]
Abstract
Polyploidization is a common phenomenon in angiosperms, and polyploidy has played a major role in the long-term diversification and evolutionary success of plants. Triploid plants are considered as the intermediate stage in the formation of stable autotetraploid plants, and this pathway of tetraploid formation is known as the triploid bridge. As for the mechanism of triploid formation among diploid populations, fusion of an unreduced gamete with a reduced gamete is generally accepted. In addition, the possibility of polyspermy has been proposed for maize, wheat and some orchids, although it has been regarded as an uncommon mechanism of polyploid formation. One of the reasons why polyspermy is regarded as uncommon is because it is difficult to reproduce the polyspermy situation in zygotes and to analyze the developmental profiles of polyspermic zygotes. In the study, we produced polyspermic rice zygotes by electric fusion of an egg cell with two sperm cells and monitored their developmental profiles. The two sperm nuclei and the egg nucleus fused into a zygotic nucleus in the polyspermic zygote, and the triploid zygote divided into a two-celled embryo via mitotic division with a typical bipolar microtubule spindle. The two-celled proembryos developed and regenerated into triploid plants. These results suggest that polyspermic plant zygotes have the potential to form triploid embryos, and that polyspermy in angiosperms might be a pathway for the formation of triploid plants.
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Affiliation(s)
- Erika Toda
- a Department of Biological Sciences , Tokyo Metropolitan University , Minami-osawa Hachioji, Tokyo , Japan
- b Plant Breeding Innovation Laboratory , RIKEN Innovation Center , Suehiro-cho, Tsurumi-ku, Yokohama , Japan
| | - Takashi Okamoto
- a Department of Biological Sciences , Tokyo Metropolitan University , Minami-osawa Hachioji, Tokyo , Japan
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Maruyama D, Ohtsu M, Higashiyama T. Cell fusion and nuclear fusion in plants. Semin Cell Dev Biol 2016; 60:127-135. [PMID: 27473789 DOI: 10.1016/j.semcdb.2016.07.024] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 07/25/2016] [Accepted: 07/26/2016] [Indexed: 10/21/2022]
Abstract
Eukaryotic cells are surrounded by a plasma membrane and have a large nucleus containing the genomic DNA, which is enclosed by a nuclear envelope consisting of the outer and inner nuclear membranes. Although these membranes maintain the identity of cells, they sometimes fuse to each other, such as to produce a zygote during sexual reproduction or to give rise to other characteristically polyploid tissues. Recent studies have demonstrated that the mechanisms of plasma membrane or nuclear membrane fusion in plants are shared to some extent with those of yeasts and animals, despite the unique features of plant cells including thick cell walls and intercellular connections. Here, we summarize the key factors in the fusion of these membranes during plant reproduction, and also focus on "non-gametic cell fusion," which was thought to be rare in plant tissue, in which each cell is separated by a cell wall.
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Affiliation(s)
- Daisuke Maruyama
- Kihara Institute for Biological Research, Yokohama City University, 641-12 Maioka-cho, Totsuka-ku, Yokohama, Kanagawa 244-0813, Japan.
| | - Mina Ohtsu
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
| | - Tetsuya Higashiyama
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; Institute of Transformative Bio-Molecules (ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; JST ERATO Higashiyama Live-Holonics Project, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
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Hybrid Sterility in Rice (Oryza sativa L.) Involves the Tetratricopeptide Repeat Domain Containing Protein. Genetics 2016; 203:1439-51. [PMID: 27182946 DOI: 10.1534/genetics.115.183848] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Accepted: 04/20/2016] [Indexed: 11/18/2022] Open
Abstract
Intersubspecific hybrid sterility is a common form of reproductive isolation in rice (Oryza sativa L.), which significantly hampers the utilization of heterosis between indica and japonica varieties. Here, we elucidated the mechanism of S7, which specially causes Aus-japonica/indica hybrid female sterility, through cytological and genetic analysis, map-based cloning, and transformation experiments. Abnormal positioning of polar nuclei and smaller embryo sac were observed in F1 compared with male and female parents. Female gametes carrying S7(cp) and S7(i) were aborted in S7(ai)/S7(cp) and S7(ai)/S7(i), respectively, whereas they were normal in both N22 and Dular possessing a neutral allele, S7(n) S7 was fine mapped to a 139-kb region in the centromere region on chromosome 7, where the recombination was remarkably suppressed due to aggregation of retrotransposons. Among 16 putative open reading frames (ORFs) localized in the mapping region, ORF3 encoding a tetratricopeptide repeat domain containing protein was highly expressed in the pistil. Transformation experiments demonstrated that ORF3 is the candidate gene: downregulated expression of ORF3 restored spikelet fertility and eliminated absolutely preferential transmission of S7(ai) in heterozygote S7(ai)/S7(cp); sterility occurred in the transformants Cpslo17-S7(ai) Our results may provide implications for overcoming hybrid embryo sac sterility in intersubspecific hybrid rice and utilization of hybrid heterosis for cultivated rice improvement.
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Toda E, Ohnishi Y, Okamoto T. Development of Polyspermic Rice Zygotes. PLANT PHYSIOLOGY 2016; 171:206-14. [PMID: 26945052 PMCID: PMC4854695 DOI: 10.1104/pp.15.01953] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 03/02/2016] [Indexed: 05/03/2023]
Abstract
Fertilization is a general feature of eukaryotic uni- and multicellular organisms to restore a diploid genome from female and male gamete haploid genomes. In most animals and fucoid algae, polyspermy block occurs at the plasmogamy step. Because the polyspermy barrier in animals and in fucoid algae is incomplete, polyspermic zygotes are generated by multiple fertilization events. However, these polyspermic zygotes with extra centrioles from multiple sperms show aberrant nuclear and cell division. In angiosperms, polyspermy block functions in the egg cell and the central cell to promote faithful double fertilization, although the mechanism of polyspermy block remains unclear. In contrast to the case in animals and fucoid algae, polyspermic zygotes formed in angiosperms are not expected to die because angiosperms lack centrosomes. However, there have been no reports on the developmental profiles of polyspermic zygotes at cellular level in angiosperms. In this study, we produced polyspermic rice zygotes by electric fusion of an egg cell with two sperm cells, and monitored their developmental profiles. Two sperm nuclei and an egg nucleus fused into a zygotic nucleus, and the triploid zygote divided into a two-celled embryo via mitotic division with a typical bipolar microtubule spindle, as observed during mitosis of a diploid zygote. The two-celled proembryos further developed and regenerated into triploid plants. These findings suggest that polyspermic plant zygotes have the potential to form triploid embryos. Polyspermy in angiosperms might be a pathway for the formation of triploid plants, which can contribute significantly to the formation of autopolyploids.
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Affiliation(s)
- Erika Toda
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo 192-0397, Japan (E.T., Y.O., T.O.)
| | - Yukinosuke Ohnishi
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo 192-0397, Japan (E.T., Y.O., T.O.)
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo 192-0397, Japan (E.T., Y.O., T.O.)
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Toda E, Ohnishi Y, Okamoto T. Electro-fusion of Gametes and Subsequent Culture of Zygotes in Rice. Bio Protoc 2016. [DOI: 10.21769/bioprotoc.2074] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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Embryogenesis and Plant Regeneration from Isolated Wheat Zygotes. Methods Mol Biol 2015; 1359:503-14. [PMID: 26619884 DOI: 10.1007/978-1-4939-3061-6_29] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Wheat zygotes can be mechanically isolated and cultivated to continue their development in vitro. Since each zygote needs to be individually isolated, only relatively few of these cells are available per experiment. To facilitate embryonic growth despite of this limitation, the zygotes are kept within a culture insert placed in a larger dish which itself contains embryogenic pollen cocultivated for continuous medium conditioning. This setup ensures that the two cultures, while being physically separated from one another, can exchange essential intercellular signal molecules passing through the bottom of the insert which is made of a permeable membrane. Thanks to the natural fate of zygotes, which is to form an embryo followed by the generation of a plant, embryogenesis and plant regeneration are achieved at much higher efficiency as compared to other single-cell systems. While the method is largely independent of the genotype, it allows for the nondestructive observation, manipulation, and individual analysis of zygotes and very young embryos.
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Baroux C, Grossniklaus U. The Maternal-to-Zygotic Transition in Flowering Plants: Evidence, Mechanisms, and Plasticity. Curr Top Dev Biol 2015; 113:351-71. [PMID: 26358878 DOI: 10.1016/bs.ctdb.2015.06.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
The maternal-to-zygotic transition (MZT) defines a developmental phase during which the embryo progressively emancipates itself from a developmental control relying largely on maternal information. The MZT is a functional readout of two processes: the clearance of maternally derived information and the de novo expression of the inherited, parental alleles enabled by zygotic genome activation (ZGA). In plants, for many years the debate about whether the MZT exists at all focused on the ZGA alone. However, several recent studies provide evidence for a progressive alleviation of the maternal control over embryogenesis that is correlated with a gradual ZGA, a process that is itself maternally controlled. Yet, several examples of zygotic genes that are expressed and/or functionally required early in embryogenesis demonstrate a certain flexibility in the dynamics and kinetics of the MZT among plant species and also intraspecific hybrids.
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Affiliation(s)
- Célia Baroux
- Institute of Plant Biology & Zurich-Basel Plant Science Center, University of Zurich, Zurich, Switzerland
| | - Ueli Grossniklaus
- Institute of Plant Biology & Zurich-Basel Plant Science Center, University of Zurich, Zurich, Switzerland.
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Kawashima T, Berger F. The central cell nuclear position at the micropylar end is maintained by the balance of F-actin dynamics, but dispensable for karyogamy in Arabidopsis. PLANT REPRODUCTION 2015; 28:103-10. [PMID: 25698518 DOI: 10.1007/s00497-015-0259-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 02/09/2015] [Indexed: 05/20/2023]
Abstract
Advances in Fertilization. In flowering plants, fertilization is initiated by the delivery of immotile sperm cells to the boundary between two female gametes, the egg cell and the central cell. During female gamete development in Arabidopsis, the nucleus of the central cell becomes positioned toward this boundary. How this specific polarized nuclear position is maintained is unclear and whether it plays a role in successful fertilization remains to be determined. By disrupting and manipulating F-actin dynamics in the central cell, we identified that the balance of F-actin dynamics is important for nuclear positioning in the central cell and that the presence of intact F-actin cables in the central cell correlates with successful karyogamy regardless of the central cell nuclear position. We also report that the surface of the central cell nucleus is enriched in F-actin. Thus, the central cell nucleus might also serve as a site that organizes F-actin cytoskeleton to promote sperm cell nucleus movement and karyogamy.
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Nagahara S, Takeuchi H, Higashiyama T. Generation of a homozygous fertilization-defective gcs1 mutant by heat-inducible removal of a rescue gene. PLANT REPRODUCTION 2015; 28:33-46. [PMID: 25673573 PMCID: PMC4333230 DOI: 10.1007/s00497-015-0256-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 01/23/2015] [Indexed: 05/10/2023]
Abstract
Key message: New gametic homozygous mutants. In angiosperms, a haploid male gamete (sperm cell) fuses with a haploid female gamete (egg cell) during fertilization to form a zygote carrying paternally and maternally derived chromosomes. Several fertilization-defective mutants in Arabidopsis thaliana, including a generative cell-specific 1 (gcs1)/hapless 2 mutant, the sperm cells of which are unable to fuse with female gametes, can only be maintained as heterozygous lines due to the infertile male or female gametes. Here, we report successful generation of a gcs1 homozygous mutant by heat-inducible removal of the GCS1 transgene. Using the gcs1 homozygous mutant as male, the defect in gamete fusion was observed with great frequency; in our direct observation by semi-in vivo fertilization assay using ovules, 100 % of discharged sperm cells in culture failed to show gamete fusion. More than 70 % of ovules in the pistil received a second pollen tube as attempted fertilization recovery. Moreover, gcs1 mutant sperm cells could fertilize female gametes at a low frequency in the pistil. This strategy to generate homozygous fertilization-defective mutants will facilitate novel approaches in plant reproduction research.
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Affiliation(s)
- Shiori Nagahara
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 Japan
| | - Hidenori Takeuchi
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 Japan
- JST ERATO Higashiyama Live-Holonics Project, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 Japan
| | - Tetsuya Higashiyama
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 Japan
- JST ERATO Higashiyama Live-Holonics Project, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 Japan
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 Japan
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Ohnishi Y, Okamoto T. Karyogamy in rice zygotes: Actin filament-dependent migration of sperm nucleus, chromatin dynamics, and de novo gene expression. PLANT SIGNALING & BEHAVIOR 2015; 10:e989021. [PMID: 25723729 PMCID: PMC4622960 DOI: 10.4161/15592324.2014.989021] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2014] [Accepted: 09/18/2014] [Indexed: 05/29/2023]
Abstract
In angiosperms, the fusion of a sperm cell with an egg cell, termed plasmogamy, triggers egg activation. Then, karyogamy, migration of the sperm nucleus toward the egg nucleus and their subsequent nuclear fusion, progresses, and de novo gene expression from the zygotic genome is initiated for early embryogenesis. Therefore, karyogamy is an important post-fusion event that bridges egg activation and de novo gene expression in fused gametes/zygotes. In this study, we monitored the progression of karyogamy in rice zygotes produced by in vitro fusion. The results indicated that the sperm nucleus migrated adjacent to the egg nucleus via an actin cytoskeleton, and the egg chromatin then appeared to move unidirectionally into the sperm nucleus through a possible nuclear connection. An enlargement of the sperm nucleus accompanied this possible chromatin remodeling. Then, 30-70 min after fusion, the sperm chromatin began to decondense, and karyogamy was completed. The development of early rice zygotes from plasmogamy to karyogamy could be divided into eight stages, and paternal and de novo synthesized transcripts were separately detectable in zygotes at early and late karyogamy stages, respectively, by RT-PCR using zygotes at each karyogamy stage.
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Affiliation(s)
- Yukinosuke Ohnishi
- Department of Biological Sciences; Tokyo Metropolitan University; Tokyo, Japan
| | - Takashi Okamoto
- Department of Biological Sciences; Tokyo Metropolitan University; Tokyo, Japan
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