1
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Mori K, Tanase K, Sasaki K. Novel electroporation-based genome editing of carnation plant tissues using RNPs targeting the anthocyanidin synthase gene. PLANTA 2024; 259:84. [PMID: 38448635 DOI: 10.1007/s00425-024-04358-6] [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: 07/26/2023] [Accepted: 02/02/2024] [Indexed: 03/08/2024]
Abstract
MAIN CONCLUSION A novel electroporation method for genome editing was performed using plant tissue samples by direct RNPs-introduction in carnation. Genome editing is becoming a very useful tool in plant breeding. In this study, a novel electroporation method was performed for genome editing using plant tissue samples. The objective was to create a flower color mutant using the pink-flowered carnation 'Kane Ainou 1-go'. For this purpose, a ribonucleoprotein consisting of guide RNA and clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein 9 (Cas9) was introduced into the stem tissue to induce mutations in the anthocyanidin synthase (ANS) gene, which is involved in anthocyanin biosynthesis. As the ANS of 'Kane Ainou 1-go' has not been previously isolated, we initially isolated the ANS gene from 'Kane Ainou 1-go' for characterization. Southern hybridization analysis confirmed that the ANS gene was present in the genome as a two-allele gene with a pair of homologous sequences (ANS-1 and 2); these sequences were used as the target for genome editing. Genome editing was performed by introducing #2_single-guide RNA into the stem tissue using the ribonucleoprotein. This molecule was used because it exhibited the highest efficiency in an analysis of cleavage activity against the target sequence in vitro. Cleaved amplified polymorphic sequence analysis of genomic DNA extracted from 85 regenerated individuals after genome editing was performed. The results indicated that mutations in the ANS gene may have been introduced into two lines. Cloning of the ANS gene in these two lines confirmed the introduction of a single nucleotide substitution mutation for ANS-1 in both lines, and a single amino acid substitution in one line. We discussed the possibility of color change by the amino acid substitution, and also the future applications of this technology.
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Affiliation(s)
- Kenichiro Mori
- Aichi Agricultural Research Center (AARC), 1-1 Sagamine Yazako, Nagakute, Aichi, 480-1193, Japan
| | - Koji Tanase
- Institute of Vegetable and Floriculture Science, National Agriculture and Food Research Organization (NARO), 2-1 Fujimoto, Tsukuba, Ibaraki, 305-0852, Japan
| | - Katsutomo Sasaki
- Institute of Vegetable and Floriculture Science, National Agriculture and Food Research Organization (NARO), 2-1 Fujimoto, Tsukuba, Ibaraki, 305-0852, Japan.
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2
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Xu H, Bartley L, Libault M, Sundaresan V, Fu H, Russell S. The roles of a novel CDKB/KRP/FB3 cell cycle core complex in rice gametes and initiation of embryogenesis. PLANT REPRODUCTION 2023; 36:301-320. [PMID: 37491485 DOI: 10.1007/s00497-023-00474-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Accepted: 06/29/2023] [Indexed: 07/27/2023]
Abstract
The cell cycle controls division and proliferation of all eukaryotic cells and is tightly regulated at multiple checkpoints by complexes of core cell cycle proteins. Due to the difficulty in accessing female gametes and zygotes of flowering plants, little is known about the molecular mechanisms underlying embryogenesis initiation despite the crucial importance of this process for seed crops. In this study, we reveal three levels of factors involved in rice zygotic cell cycle control and characterize their functions and regulation. Protein-protein interaction studies, including within zygote cells, and in vitro biochemical analyses delineate a model of the zygotic cell cycle core complex for rice. In this model, CDKB1, a major regulator of plant mitosis, is a cyclin (CYCD5)-dependent kinase; its activity is coordinately inhibited by two cell cycle inhibitors, KRP4 and KRP5; and both KRPs are regulated via F-box protein 3 (FB3)-mediated proteolysis. Supporting their critical roles in controlling the rice zygotic cell cycle, mutations in KRP4, KRP5 and FB3 result in the compromised function of sperm cells and abnormal organization of female germ units, embryo and endosperm, thus significantly reducing seed-set rate. This work helps reveal regulatory mechanisms controlling the zygotic cell cycle toward seed formation in angiosperms.
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Affiliation(s)
- Hengping Xu
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, 73019, USA.
| | - Laura Bartley
- Institute of Biological Chemistry, Washington State University, Pullman, WA, 99164, USA
| | - Marc Libault
- Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE, 68503, USA
| | | | - Hong Fu
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, 73019, USA
| | - Scott Russell
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, 73019, USA
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3
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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: 0] [Impact Index Per Article: 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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4
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Rogo U, Fambrini M, Pugliesi C. Embryo Rescue in Plant Breeding. PLANTS (BASEL, SWITZERLAND) 2023; 12:3106. [PMID: 37687352 PMCID: PMC10489947 DOI: 10.3390/plants12173106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 08/14/2023] [Accepted: 08/19/2023] [Indexed: 09/10/2023]
Abstract
Embryo rescue (ER) techniques are among the oldest and most successful in vitro tissue culture protocols used with plant species. ER refers to a series of methods that promote the development of an immature or lethal embryo into a viable plant. Intraspecific, interspecific, or intergeneric crosses allow the introgression of important alleles of agricultural interest from wild species, such as resistance or tolerance to abiotic and biotic stresses or morphological traits in crops. However, pre-zygotic and post-zygotic reproductive barriers often present challenges in achieving successful hybridization. Pre-zygotic barriers manifest as incompatibility reactions that hinder pollen germination, pollen tube growth, or penetration into the ovule occurring in various tissues, such as the stigma, style, or ovary. To overcome these barriers, several strategies are employed, including cut-style or graft-on-style techniques, the utilization of mixed pollen from distinct species, placenta pollination, and in vitro ovule pollination. On the other hand, post-zygotic barriers act at different tissues and stages ranging from early embryo development to the subsequent growth and reproduction of the offspring. Many crosses among different genera result in embryo abortion due to the failure of endosperm development. In such cases, ER techniques are needed to rescue these hybrids. ER holds great promise for not only facilitating successful crosses but also for obtaining haploids, doubled haploids, and manipulating the ploidy levels for chromosome engineering by monosomic and disomic addition as well substitution lines. Furthermore, ER can be used to shorten the reproductive cycle and for the propagation of rare plants. Additionally, it has been repeatedly used to study the stages of embryonic development, especially in embryo-lethal mutants. The most widely used ER procedure is the culture of immature embryos taken and placed directly on culture media. In certain cases, the in vitro culture of ovule, ovaries or placentas enables the successful development of young embryos from the zygote stage to maturity.
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Affiliation(s)
| | | | - Claudio Pugliesi
- Department of Agriculture Food and Environment, University of Pisa, Via del Borghetto 80, 56124 Pisa, Italy; (U.R.); (M.F.)
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5
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Ichikawa M, Kato N, Toda E, Kashihara M, Ishida Y, Hiei Y, Isobe SN, Shirasawa K, Hirakawa H, Okamoto T, Komari T. Whole-genome sequence analysis of mutations in rice plants regenerated from zygotes, mature embryos, and immature embryos. BREEDING SCIENCE 2023; 73:349-353. [PMID: 37840979 PMCID: PMC10570880 DOI: 10.1270/jsbbs.22100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Accepted: 02/25/2023] [Indexed: 10/17/2023]
Abstract
Somaclonal variation was studied by whole-genome sequencing in rice plants (Oryza sativa L., 'Nipponbare') regenerated from the zygotes, mature embryos, and immature embryos of a single mother plant. The mother plant and its seed-propagated progeny were also sequenced. A total of 338 variants of the mother plant sequence were detected in the progeny, and mean values ranged from 9.0 of the seed-propagated plants to 37.4 of regenerants from mature embryos. The natural mutation rate of 1.2 × 10-8 calculated using the variants in the seed-propagated plants was consistent with the values reported previously. The ratio of single nucleotide variants (SNVs) among the variants in the seed-propagated plants was 91.1%, which is higher than 56.1% previously reported, and not significantly different from those in the regenerants. Overall, the ratio of transitions to transversions of SNVs was lower in the regenerants as shown previously. Plants regenerated from mature embryos had significantly more variants than different progeny types. Therefore, using zygotes and immature embryos can reduce somaclonal variation during the genetic manipulation of rice.
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Affiliation(s)
- Masako Ichikawa
- Plant Innovation Center, Japan Tobacco Inc., 700 Higashibara, Iwata, Shizuoka 438-0802, Japan
- Agri-Bio Research Center, KANEKA CORPORATION, 700 Higashibara, Iwata, Shizuoka 438-0802, Japan
| | - Norio Kato
- Plant Innovation Center, Japan Tobacco Inc., 700 Higashibara, Iwata, Shizuoka 438-0802, Japan
- 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 192-0397, Japan
| | - Erika Toda
- 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 192-0397, Japan
- Department of Biological Sciences, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Masakazu Kashihara
- Plant Innovation Center, Japan Tobacco Inc., 700 Higashibara, Iwata, Shizuoka 438-0802, Japan
- Agri-Bio Research Center, KANEKA CORPORATION, 700 Higashibara, Iwata, Shizuoka 438-0802, Japan
| | - Yuji Ishida
- Plant Innovation Center, Japan Tobacco Inc., 700 Higashibara, Iwata, Shizuoka 438-0802, Japan
- Agri-Bio Research Center, KANEKA CORPORATION, 700 Higashibara, Iwata, Shizuoka 438-0802, Japan
| | - Yukoh Hiei
- Plant Innovation Center, Japan Tobacco Inc., 700 Higashibara, Iwata, Shizuoka 438-0802, Japan
| | - Sachiko N. Isobe
- Kazusa DNA Research Institute, 2-6-7 Kazusa-kamatari, Kisarazu, Chiba 292-0818, Japan
| | - Kenta Shirasawa
- Kazusa DNA Research Institute, 2-6-7 Kazusa-kamatari, Kisarazu, Chiba 292-0818, Japan
| | - Hideki Hirakawa
- Kazusa DNA Research Institute, 2-6-7 Kazusa-kamatari, Kisarazu, Chiba 292-0818, Japan
| | - Takashi Okamoto
- 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 192-0397, Japan
| | - Toshihiko Komari
- Plant Innovation Center, Japan Tobacco Inc., 700 Higashibara, Iwata, Shizuoka 438-0802, Japan
- Agri-Bio Research Center, KANEKA CORPORATION, 700 Higashibara, Iwata, Shizuoka 438-0802, Japan
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6
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Flores-Tornero M, Becker JD. 50 years of sperm cell isolations: from structural to omic studies. JOURNAL OF EXPERIMENTAL BOTANY 2023:erad117. [PMID: 37025026 DOI: 10.1093/jxb/erad117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Indexed: 06/19/2023]
Abstract
The fusion of male and female gametes is a fundamental process in the perpetuation and diversification of species. During the last 50 years, significant efforts have been made to isolate and characterize sperm cells from flowering plants, and to identify how these cells interact with female gametes to achieve double fertilization. The first techniques and analytical approaches not only provided structural and biochemical characterizations of plant sperm cells but also paved the way for in vitro fertilization studies. Further technological advances then led to unique insights into sperm biology at transcriptomic, proteomic and epigenetic level. Starting with a historical overview of sperm cell isolation techniques, we provide examples of how these contributed to create our current knowledge of sperm cell biology, and point out remaining challenges.
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Affiliation(s)
- María Flores-Tornero
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, Oeiras, 2780-157 Portugal
| | - Jörg D Becker
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, Oeiras, 2780-157 Portugal
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7
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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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8
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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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9
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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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11
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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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12
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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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13
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Cable J, Ronald PC, Voytas D, Zhang F, Levy AA, Takatsuka A, Arimura SI, Jacobsen SE, Toki S, Toda E, Gao C, Zhu JK, Boch J, Van Eck J, Mahfouz M, Andersson M, Fridman E, Weiss T, Wang K, Qi Y, Jores T, Adams T, Bagchi R. Plant genome engineering from lab to field-a Keystone Symposia report. Ann N Y Acad Sci 2021; 1506:35-54. [PMID: 34435370 DOI: 10.1111/nyas.14675] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 07/14/2021] [Indexed: 12/30/2022]
Abstract
Facing the challenges of the world's food sources posed by a growing global population and a warming climate will require improvements in plant breeding and technology. Enhancing crop resiliency and yield via genome engineering will undoubtedly be a key part of the solution. The advent of new tools, such as CRIPSR/Cas, has ushered in significant advances in plant genome engineering. However, several serious challenges remain in achieving this goal. Among them are efficient transformation and plant regeneration for most crop species, low frequency of some editing applications, and high attrition rates. On March 8 and 9, 2021, experts in plant genome engineering and breeding from academia and industry met virtually for the Keystone eSymposium "Plant Genome Engineering: From Lab to Field" to discuss advances in genome editing tools, plant transformation, plant breeding, and crop trait development, all vital for transferring the benefits of novel technologies to the field.
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Affiliation(s)
| | - Pamela C Ronald
- Department of Plant Pathology, University of California, Davis, and the Joint BioEnergy Institute, Davis, California
| | - Daniel Voytas
- Department of Genetics, Cell Biology and Development; Center for Precision Plant Genomics; and Center for Genome Engineering, University of Minnesota, St. Paul, Minnesota
| | - Feng Zhang
- College of Biological Sciences, University of Minnesota, St. Paul, Minnesota
| | - Avraham A Levy
- Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Ayumu Takatsuka
- Graduate School of Agricultural Science, Tohoku University, Sendai, Japan
| | - Shin-Ichi Arimura
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Steven E Jacobsen
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research; Department of Molecular, Cell and Developmental Biology; and Howard Hughes Medical Institute, University of California, Los Angeles, California
| | - Seiichi Toki
- Division of Applied Genetics, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Tsukuba, Japan
| | - Erika Toda
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, Japan
| | - Caixia Gao
- State Key Laboratory of Plant Cell and Chromosome Engineering, Center for Genome Editing, Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, and College of Advanced Agricultural Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Jian-Kang Zhu
- Shanghai Center for Plant Stress Biology, Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Jens Boch
- Department of Plant Biotechnology, Leibniz Universität Hannover, Hannover, Germany
| | - Joyce Van Eck
- The Boyce Thompson Institute, Ithaca, New York, and Plant Breeding and Genetics Section, Cornell University, Ithaca, New York
| | - Magdy Mahfouz
- Laboratory for Genome Engineering and Synthetic Biology, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia
| | - Mariette Andersson
- Department of Plant Breeding, Swedish University of Agricultural Sciences, Alnarp, Sweden
| | - Eyal Fridman
- Institute of Plant Sciences, Agricultural Research Organization (ARO), The Volcani Center, Bet Dagan, Israel
| | - Trevor Weiss
- Department of Genetics, Cell Biology and Development; Center for Precision Plant Genomics; and Center for Genome Engineering, University of Minnesota, St. Paul, Minnesota
| | - Kan Wang
- Department of Agronomy, Iowa State University, Ames, Iowa
| | - Yiping Qi
- Department of Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland, and Institute for Bioscience and Biotechnology Research, University of Maryland, Rockville, Maryland
| | - Tobias Jores
- Department of Genome Sciences, University of Washington, Seattle, Washington
| | | | - Rammyani Bagchi
- Department of Nanoscience, The University of North Carolina at Greensboro, Greensboro, North Carolina
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14
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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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15
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Toda E, Okamoto T. Gene Expression and Genome Editing Systems by Direct Delivery of Macromolecules Into Rice Egg Cells and Zygotes. Bio Protoc 2020; 10:e3681. [PMID: 33659352 PMCID: PMC7842353 DOI: 10.21769/bioprotoc.3681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Revised: 05/05/2020] [Accepted: 05/09/2020] [Indexed: 11/02/2022] Open
Abstract
Polyethylene glycol calcium (PEG-Ca2+)-mediated transfection allows rapid and efficient examination to analyze diverse cellular functions of genes of interest. In plant cells, macromolecules, such as DNA, RNA and protein, are delivered into protoplasts derived from somatic tissues or calli via PEG-Ca2+ transfection. To broaden and develop the scope of investigations using plant gametes and zygotes, a procedure for direct delivery of macromolecules into these cells has recently been established using PEG-Ca2+ transfection. This PEG-Ca2+-mediated delivery into rice egg cells/zygotes consists of four microtechniques, (i) isolation of gametes, (ii) production of zygotes by electrofusion of gametes, (iii) PEG-Ca2+-mediated delivery of macromolecules into isolated egg cells or produced zygotes, and (iv) culture and subsequent analyses of the transfected egg cells/zygotes. Because the full protocol for microtechniques (i) and (ii) have already been reported in Toda et al., 2016 , microtechniques (iii) and (iv) are mainly described in this protocol.
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Affiliation(s)
- Erika Toda
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, 192-0397, Japan
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo, 192-0397, Japan
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16
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Toda E, Okamoto T. CRISPR/Cas9‐Based Genome Editing Using Rice Zygotes. ACTA ACUST UNITED AC 2020; 5:e20111. [DOI: 10.1002/cppb.20111] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Erika Toda
- Department of Biological SciencesTokyo Metropolitan University Hachioji Tokyo Japan
| | - Takashi Okamoto
- Department of Biological SciencesTokyo Metropolitan University Hachioji Tokyo Japan
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17
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Abstract
The isolation of male and female gametes is an effective method to study the fertilization mechanisms of higher plants. An osmotic shock method was used to rupture pollen grains of Allium tuberosum Roxb and release the pollen contents, including generative cells, which were mass collected. The pollinated styles were cut following 3 h of in vivo growth, and cultured in medium for 6-8 h, during which time pollen tubes grew out of the cut end of the style. After pollen tubes were transferred into a solution containing 6% mannitol, tubes burst and released pairs of sperm cells. Ovules of A. tuberosum were incubated in an enzyme solution for 30 min, and then dissected to remove the integuments. Following transfer to a dissecting solution free of enzymes, each nucellus was cut in the middle, and squeezed gently on the micropylar end, resulting in the liberation of the egg, zygote and proembryo from ovules at selected stages. These cells can be used to explore fertilization and embryonic development using molecular biological methods for each cell type and development stage.
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18
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Deng W, Cheng C, Luo C, Yang SJ. Isolation of the sperm and egg cells in wild rice (Oryza officinalis) as a mechanism for crop improvement. PLANT REPRODUCTION 2020; 33:35-40. [PMID: 31997012 DOI: 10.1007/s00497-020-00383-z] [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: 09/24/2019] [Accepted: 01/10/2020] [Indexed: 06/10/2023]
Abstract
Sperm cells can be isolated from the mature pollen grains of medicinal wild rice (Oryza officinalis) using an osmotic shock method, and the viable egg cells can be isolated by enzymatic digestion and mechanical dissection steps. Favorable alleles for rice breeding have been identified in natural cultivars and wild rice by association analysis of known functional genes with target trait performance. Transferring these genes from wild rice into cultivated rice varieties is one of the important objectives for rice breeders. The isolation of the sperm and egg cells of wild and cultivated rice is a prerequisite for the in vitro hybridization of distantly related cultivated rice and wild rice lines. Here, we provide a technical approach for isolating the sperm and egg cells of wild rice (Oryza officinalis). In this method, sperm cells were isolated from the mature pollen grains of medicinal wild rice (O. officinalis) according to an osmotic shock method. Additionally, viable O. officinalis egg cells were isolated following enzymatic digestion and mechanical dissection steps. Specifically, ovules were digested in an enzymatic solution containing pectinase and cellulase for 30 min, after which the ovule was cut into two halves. Three egg apparatus cells were released by gently applying pressure to the micropylar end. Generally, six or seven egg cells could be isolated from 20 ovules in 60 min. The same method was used to isolate zygotes from flowers at 24 h after pollination. This technology solved the difficulty of isolating sperm and egg cells in O. officinalis and allowed the isolated sperm and egg cells to be combined by in vitro hybridization of distantly related wild and cultivated rice lines.
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Affiliation(s)
- Wei Deng
- School of Life Sciences, Xiamen University, Xiamen, 361005, China
| | - Cheng Cheng
- School of Life Sciences, Xiamen University, Xiamen, 361005, China
| | - Chengke Luo
- School of Agricultural Science, Ningxia University, Yinchuan, 750021, China
| | - Shu Juan Yang
- School of Life Science, Ningxia University, Yinchuan, 750021, China.
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19
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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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20
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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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21
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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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22
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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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23
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Abstract
SummaryIsolated gametes can be used to investigate fertilization mechanisms, and probe distant hybridization between different species. Pollen grains of wheat and Setaria viridis are tricellular, containing sperm cells at anthesis. Sperm from these plants were isolated by breaking open pollen grains in a osmotic solution. Wheat ovules were digested in an enzyme solution for 20 min, and then transferred to an isolation solution without enzymes to separate egg cells from ovules. The fusion of wheat egg cells with wheat and S. viridis sperm was conducted using an electro-fusion apparatus. Under suitable osmotic pressure (10% mannitol), calcium concentration of 0.001% (CaCl2·2H2O), and a 30-35 V alternating electric field for 15 s, egg cells and sperm adhered to each other and became arranged in a line. Electroporation of the plasma membrane of egg cells and sperm using a 300-500 V direct-current electric field (45 µs amplitude pulse) caused them to fuse.
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24
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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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25
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Toda E, Koiso N, Takebayashi A, Ichikawa M, Kiba T, Osakabe K, Osakabe Y, Sakakibara H, Kato N, Okamoto T. An efficient DNA- and selectable-marker-free genome-editing system using zygotes in rice. NATURE PLANTS 2019; 5:363-368. [PMID: 30911123 DOI: 10.1038/s41477-019-0386-z] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Accepted: 02/13/2019] [Indexed: 05/18/2023]
Abstract
Technology involving the targeted mutagenesis of plants using programmable nucleases has been developing rapidly and has enormous potential in next-generation plant breeding. Notably, the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated protein-9 nuclease (Cas9) (CRISPR-Cas9) system has paved the way for the development of rapid and cost-effective procedures to create new mutant populations in plants1,2. Although genome-edited plants from multiple species have been produced successfully using a method in which a Cas9-guide RNA (gRNA) expression cassette and selectable marker are integrated into the genomic DNA by Agrobacterium tumefaciens-mediated transformation or particle bombardment3, CRISPR-Cas9 integration increases the chance of off-target modifications4, and foreign DNA sequences cause legislative concerns about genetically modified organisms5. Therefore, DNA-free genome editing has been developed, involving the delivery of preassembled Cas9-gRNA ribonucleoproteins (RNPs) into protoplasts derived from somatic tissues by polyethylene glycol-calcium (PEG-Ca2+)-mediated transfection in tobacco, Arabidopsis, lettuce, rice6, Petunia7, grapevine, apple8 and potato9, or into embryo cells by biolistic bombardment in maize10 and wheat11. However, the isolation and culture of protoplasts is not feasible in most plant species and the frequency of obtaining genome-edited plants through biolistic bombardment is relatively low. Here, we report a genome-editing system via direct delivery of Cas9-gRNA RNPs into plant zygotes. Cas9-gRNA RNPs were transfected into rice zygotes produced by in vitro fertilization of isolated gametes12 and the zygotes were cultured into mature plants in the absence of selection agents, resulting in the regeneration of rice plants with targeted mutations in around 14-64% of plants. This efficient plant-genome-editing system has enormous potential for the improvement of rice as well as other important crop species.
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Affiliation(s)
- Erika Toda
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Technology and Innovation Hub, Yokohama, Japan.
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Japan.
| | - Narumi Koiso
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Japan
| | - Arika Takebayashi
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Technology and Innovation Hub, Yokohama, Japan
| | | | - Takatoshi Kiba
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Technology and Innovation Hub, Yokohama, Japan
| | - Keishi Osakabe
- Faculty of Bioscience and Bioindustry, Tokushima University, Tokushima, Japan
| | - Yuriko Osakabe
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Technology and Innovation Hub, Yokohama, Japan
- Faculty of Bioscience and Bioindustry, Tokushima University, Tokushima, Japan
| | - Hitoshi Sakakibara
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Technology and Innovation Hub, Yokohama, Japan
| | - Norio Kato
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Technology and Innovation Hub, Yokohama, Japan
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Japan
- Plant Innovation Center, Japan Tobacco Inc., Iwata, Japan
| | - Takashi Okamoto
- Plant Breeding Innovation Laboratory, RIKEN Cluster for Science, Technology and Innovation Hub, Yokohama, Japan.
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, 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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Li C, Xu H, Russell SD, Sundaresan V. Step-by-step protocols for rice gamete isolation. PLANT REPRODUCTION 2019; 32:5-13. [PMID: 30756188 DOI: 10.1007/s00497-019-00363-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 01/28/2019] [Indexed: 06/09/2023]
Abstract
A detailed, step-by-step protocol for isolation of rice gametes for transcriptional profiling, with a general workflow that includes controls for RNA contamination from surrounding cells and tissues is presented. Characterization of the transcriptome and other -omics studies of flowering plant gametes are challenging as a consequence of the small sizes and relative inaccessibility of these cells. Collecting such poorly represented cells is also complicated by potential contamination from surrounding sporophytic, adjacent gametophytic tissues and difficulties in extracting high-quality intact cells. Here we present detailed, step-by-step procedures for collecting intact, unfixed rice (Oryza sativa) egg cells and sperm cells without enzymatic treatments. In addition, we also present a general workflow for assessing sample purity by RT-PCR, using primers specific for marker genes preferentially expressed in surrounding cells and tissues. These protocols should facilitate future studies of genome-scale characterization of gametes in this important model crop.
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Affiliation(s)
- Chenxin Li
- Department of Plant Biology, University of California, Davis, CA, 95616, USA
| | - Hengping Xu
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, 73019, USA
| | - Scott D Russell
- Department of Microbiology and Plant Biology, University of Oklahoma, Norman, OK, 73019, USA.
| | - Venkatesan Sundaresan
- Department of Plant Biology, University of California, Davis, CA, 95616, USA.
- Department of Plant Sciences, University of California, Davis, CA, 95616, USA.
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28
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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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29
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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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30
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Kurihara D, Kimata Y, Higashiyama T, Ueda M. In Vitro Ovule Cultivation for Live-cell Imaging of Zygote Polarization and Embryo Patterning in Arabidopsis thaliana. J Vis Exp 2017. [PMID: 28930998 DOI: 10.3791/55975] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
In most flowering plants, the zygote and embryo are hidden deep in the mother tissue, and thus it has long been a mystery of how they develop dynamically; for example, how the zygote polarizes to establish the body axis and how the embryo specifies various cell fates during organ formation. This manuscript describes an in vitro ovule culture method to perform live-cell imaging of developing zygotes and embryos of Arabidopsis thaliana. The optimized cultivation medium allows zygotes or early embryos to grow into fertile plants. By combining it with a poly(dimethylsiloxane) (PDMS) micropillar array device, the ovule is held in the liquid medium in the same position. This fixation is crucial to observe the same ovule under a microscope for several days from the zygotic division to the late embryo stage. The resulting live-cell imaging can be used to monitor the real-time dynamics of zygote polarization, such as nuclear migration and cytoskeleton rearrangement, and also the cell division timing and cell fate specification during embryo patterning. Furthermore, this ovule cultivation system can be combined with inhibitor treatments to analyze the effects of various factors on embryo development, and with optical manipulations such as laser disruption to examine the role of cell-cell communication.
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Affiliation(s)
- Daisuke Kurihara
- Division of Biological Science, Graduate School of Science, Nagoya University; Higashiyama Live-Holonics Project, JST-ERATO, Nagoya University;
| | - Yusuke Kimata
- Division of Biological Science, Graduate School of Science, Nagoya University
| | - Tetsuya Higashiyama
- Division of Biological Science, Graduate School of Science, Nagoya University; Higashiyama Live-Holonics Project, JST-ERATO, Nagoya University; Institute of Transformative Bio-Molecules (ITbM), Nagoya University
| | - Minako Ueda
- Division of Biological Science, Graduate School of Science, Nagoya University; Institute of Transformative Bio-Molecules (ITbM), Nagoya University;
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31
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Koiso N, Toda E, Ichikawa M, Kato N, Okamoto T. Development of gene expression system in egg cells and zygotes isolated from rice and maize. PLANT DIRECT 2017; 1:e00010. [PMID: 31245659 PMCID: PMC6508540 DOI: 10.1002/pld3.10] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Revised: 07/10/2017] [Accepted: 07/28/2017] [Indexed: 05/25/2023]
Abstract
Polyethylene glycol calcium (PEG-Ca2+) transfection-mediated analysis allows rapid and efficient examination of gene function. To investigate the diverse cellular functions of genes of interest in plant cells, macromolecules, such as DNA, RNA, and proteins, are delivered into protoplasts prepared from somatic tissues or calli using a PEG-Ca2+ transfection procedure. To take advantage of this macromolecule delivery system in the reproductive and developmental biology of angiosperms, this study established a PEG-Ca2+ transfection system with isolated egg cells and zygotes. The conditions for PEG and plasmid DNA concentrations for transfection of rice egg cells were first addressed, and ~30% of PEG-Ca2+-transfected egg cells showed exogenous and transient expressions of fluorescent proteins from plasmid DNA delivered into the cells. Interestingly, a dual expression of two different fluorescent proteins in the same egg cell using two kinds of plasmid DNAs was also observed. For PEG-Ca2+ transfection with maize zygotes, ~80% of zygotes showed expression of GFP proteins from plasmid DNA. Importantly, PEG-transfected zygotes developed normally into cell masses and mature plants. These results suggest that the present PEG-Ca2+-mediated transient expression system provides a novel and effective platform for expressing and analyzing genes of interest in egg cells and zygotes. Moreover, combined with the CRISPR/Cas9 approach, the present transient expression system in zygotes will become a powerful and alternative tool for the preparation of gene-edited plants.
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Affiliation(s)
- Narumi Koiso
- Department of Biological SciencesTokyo Metropolitan UniversityHachiojiTokyoJapan
| | - Erika Toda
- Department of Biological SciencesTokyo Metropolitan UniversityHachiojiTokyoJapan
- Plant Breeding Innovation LaboratoryRIKEN Innovation CenterTsurumiYokohamaJapan
| | | | - Norio Kato
- Department of Biological SciencesTokyo Metropolitan UniversityHachiojiTokyoJapan
- Plant Breeding Innovation LaboratoryRIKEN Innovation CenterTsurumiYokohamaJapan
- Plant Innovation CenterJapan Tobacco Inc.IwataShizuokaJapan
| | - Takashi Okamoto
- Department of Biological SciencesTokyo Metropolitan UniversityHachiojiTokyoJapan
- Plant Breeding Innovation LaboratoryRIKEN Innovation CenterTsurumiYokohamaJapan
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32
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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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33
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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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34
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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: 13] [Impact Index Per Article: 1.9] [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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35
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Yan G, Liu H, Wang H, Lu Z, Wang Y, Mullan D, Hamblin J, Liu C. Accelerated Generation of Selfed Pure Line Plants for Gene Identification and Crop Breeding. FRONTIERS IN PLANT SCIENCE 2017; 8:1786. [PMID: 29114254 PMCID: PMC5660708 DOI: 10.3389/fpls.2017.01786] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Accepted: 10/02/2017] [Indexed: 05/18/2023]
Abstract
Production of pure lines is an important step in biological studies and breeding of many crop plants. The major types of pure lines for biological studies and breeding include doubled haploid (DH) lines, recombinant inbred lines (RILs), and near isogenic lines (NILs). DH lines can be produced through microspore and megaspore culture followed by chromosome doubling while RILs and NILs can be produced through introgressions or repeated selfing of hybrids. DH approach was developed as a quicker method than conventional method to produce pure lines. However, its drawbacks of genotype-dependency and only a single chance of recombination limited its wider application. A recently developed fast generation cycling system (FGCS) achieved similar times to those of DH for the production of selfed pure lines but is more versatile as it is much less genotype-dependent than DH technology and does not restrict recombination to a single event. The advantages and disadvantages of the technologies and their produced pure line populations for different purposes of biological research and breeding are discussed. The development of a concept of complete in vitro meiosis and mitosis system is also proposed. This could integrate with the recently developed technologies of single cell genomic sequencing and genome wide selection, leading to a complete laboratory based pre-breeding scheme.
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Affiliation(s)
- Guijun Yan
- Faculty of Science, UWA School of Agriculture and Environment, University of Western Australia, Perth, WA, Australia
- The UWA Institute of Agriculture, University of Western Australia, Crawley, WA, Australia
- *Correspondence: Guijun Yan
| | - Hui Liu
- Faculty of Science, UWA School of Agriculture and Environment, University of Western Australia, Perth, WA, Australia
- The UWA Institute of Agriculture, University of Western Australia, Crawley, WA, Australia
| | - Haibo Wang
- Hebei Centre of Plant Genetic Engineering, Institute of Genetics and Physiology, Hebei Academy of Agricultural and Forestry Sciences, Shijiazhuang, China
| | - Zhanyuan Lu
- Inner Mongolia Academy of Agriculture and Animal Husbandry Sciences, Huhhot, China
| | - Yanxia Wang
- Hebei Province Wheat Engineering Technical Research Center, Shijiazhuang Academy of Agricultural Sciences, Shijiazhuang, China
| | - Daniel Mullan
- Faculty of Science, UWA School of Agriculture and Environment, University of Western Australia, Perth, WA, Australia
- The UWA Institute of Agriculture, University of Western Australia, Crawley, WA, Australia
- InterGrain Pty. Ltd., Bibra Lake, WA, Australia
| | - John Hamblin
- Faculty of Science, UWA School of Agriculture and Environment, University of Western Australia, Perth, WA, Australia
- The UWA Institute of Agriculture, University of Western Australia, Crawley, WA, Australia
- SuperSeeds Technologies Pty. Ltd., Perth, WA, Australia
| | - Chunji Liu
- Faculty of Science, UWA School of Agriculture and Environment, University of Western Australia, Perth, WA, Australia
- The UWA Institute of Agriculture, University of Western Australia, Crawley, WA, Australia
- Commonwealth Scientific and Industrial Research Organisation Agriculture and Food, St. Lucia, QLD, Australia
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Abstract
In angiosperms, female gamete differentiation, fertilization, and subsequent zygotic development occur in embryo sacs deeply embedded in the ovaries. Despite their importance in plant reproduction and development, how the egg cell is specialized, fuses with the sperm cell, and converts into an active zygote for early embryogenesis remains unclear. Proteins enriched in each cell type are thought to reflect the biological function of the cells, since the composition of cellular proteins generally differs depending on cell type. Therefore, proteins enriched in gametes, egg and sperm cells, should have a role in reproductive and/or developmental processes, such as gamete differentiation, gamete fusion, egg activation, and early zygotic development. In this chapter, a method for identification of proteins enriched in rice gametes is first explained, and then functional analyses for these proteins using rice and Arabidopsis lines with mutations in genes encoding the putative gamete-enriched proteins are also described.
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Affiliation(s)
- Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa 1-1, Hachioji, Tokyo, 192-0397, Japan.
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37
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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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38
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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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39
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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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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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Yoon J, Cho LH, Kim SL, Choi H, Koh HJ, An G. The BEL1-type homeobox gene SH5 induces seed shattering by enhancing abscission-zone development and inhibiting lignin biosynthesis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2014; 79:717-28. [PMID: 24923192 DOI: 10.1111/tpj.12581] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Revised: 05/26/2014] [Accepted: 06/02/2014] [Indexed: 05/05/2023]
Abstract
Seed shattering is an important trait that influences grain yield. A major controlling quantitative trait locus in rice is qSH1. Although the degree of shattering is correlated with the level of expression of qSH1, some qSH1-defective cultivars display moderate shattering while others show a non-shattering phenotype. Os05 g38120 (SH5) on chromosome 5 is highly homologous to qSH1. Although we detected SH5 transcripts in various organs, this gene was highly expressed at the abscission zone (AZ) in the pedicels. When expression of this gene was suppressed in easy-shattering 'Kasalath', development of the AZ was reduced and thereby so was seed loss. By contrast, the extent of shattering, as well as AZ development, was greatly enhanced in moderate-shattering 'Dongjin' rice when SH5 was overexpressed. Likewise, overexpression of SH5 in the non-shattering 'Ilpum' led to an increase in seed shattering because lignin levels were decreased in the basal region of spikelets in the absence of development of an AZ. We also determined that two shattering-related genes, SHAT1 and Sh4, which are necessary for proper formation of an AZ, were induced by SH5. Based on these observations, we propose that SH5 modulates seed shattering by enhancing AZ development and inhibiting lignin biosynthesis.
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Affiliation(s)
- Jinmi Yoon
- Crop Biotech Institute, Kyung Hee University, Yongin, 446-701, Korea; Department of Life Science, Pohang University of Science and Technology, Pohang, 790-784, Korea
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Ohnishi Y, Hoshino R, Okamoto T. Dynamics of Male and Female Chromatin during Karyogamy in Rice Zygotes. PLANT PHYSIOLOGY 2014; 165:1533-1543. [PMID: 24948834 PMCID: PMC4119036 DOI: 10.1104/pp.114.236059] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Accepted: 06/14/2014] [Indexed: 05/20/2023]
Abstract
In angiosperms, the conversion of an egg cell into a zygote involves two sequential gametic processes: plasmogamy, the fusion of the plasma membranes of male and female gametes, and karyogamy, the fusion of the gametic nuclei. In this study, the nuclei and nuclear membranes of rice (Oryza sativa) gametes were fluorescently labeled using histones 2B-green fluorescent protein/red fluorescent protein and Sad1/UNC-84-domain protein2-green fluorescent protein, respectively, which were heterologously expressed. These gametes were fused in vitro to produce zygotes, and the nuclei and nuclear membranes in the zygotes were observed during karyogamy. The results indicated that the sperm nucleus migrates adjacent to the egg nucleus 5 to 10 min after plasmogamy via an actin cytoskelton, and the egg chromatin then appears to move unidirectionally into the sperm nucleus through a possible nuclear connection. The enlargement of the sperm nucleus accompanies this possible chromatin remodeling. Then, 30 to 70 min after fusion, the sperm chromatin begins to decondense with the completion of karyogamy. Based on these observations, the development of early rice zygotes from plasmogamy to karyogamy was divided into eight stages, and using reverse transcription PCR analyses, paternal and de novo synthesized transcripts were separately detected in zygotes at early and late karyogamy stages, respectively.
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Affiliation(s)
- Yukinosuke Ohnishi
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Rina Hoshino
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo 192-0397, Japan
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De La Fuente GN, Frei UK, Lübberstedt T. Accelerating plant breeding. TRENDS IN PLANT SCIENCE 2013; 18:667-72. [PMID: 24080381 DOI: 10.1016/j.tplants.2013.09.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 08/29/2013] [Accepted: 09/05/2013] [Indexed: 05/18/2023]
Abstract
The growing demand for food with limited arable land available necessitates that the yield of major food crops continues to increase over time. Advances in marker technology, predictive statistics, and breeding methodology have allowed for continued increases in crop performance through genetic improvement. However, one major bottleneck is the generation time of plants, which is biologically limited and has not been improved since the introduction of doubled haploid technology. In this opinion article, we propose to implement in vitro nurseries, which could substantially shorten generation time through rapid cycles of meiosis and mitosis. This could prove a useful tool for speeding up future breeding programs with the aim of sustainable food production.
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Affiliation(s)
- Gerald N De La Fuente
- Department of Agronomy, Iowa State University, 100 Osborn Drive, Ames, IA 50011, USA.
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Abiko M, Maeda H, Tamura K, Hara-Nishimura I, Okamoto T. Gene expression profiles in rice gametes and zygotes: identification of gamete-enriched genes and up- or down-regulated genes in zygotes after fertilization. JOURNAL OF EXPERIMENTAL BOTANY 2013; 64:1927-40. [PMID: 23570690 PMCID: PMC3638821 DOI: 10.1093/jxb/ert054] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
In angiosperms, fertilization and subsequent zygotic development occur in embryo sacs deeply embedded in the ovaries; therefore, these processes are poorly elucidated. In this study, microarray-based transcriptome analyses were conducted on rice sperm cells, egg cells, and zygotes isolated from flowers to identify candidate genes involved in gametic and/or early zygotic development. Cell type-specific transcriptomes were obtained, and up- or down-regulated genes in zygotes after fertilization were identified, in addition to genes enriched in male and female gametes. A total of 325 putatively up-regulated and 94 putatively down-regulated genes in zygotes were obtained. Interestingly, several genes encoding homeobox proteins or transcription factors were identified as highly up-regulated genes after fertilization, and the gene ontology for up-regulated genes was highly enriched in functions related to chromatin/DNA organization and assembly. Because a gene encoding methyltransferase 1 was identified as a highly up-regulated gene in zygotes after fertilization, the effect of an inhibitor of this enzyme on zygote development was monitored. The inhibitor appeared partially to affect polarity or division asymmetry in rice zygotes, but it did not block normal embryo generation.
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Affiliation(s)
- Mafumi Abiko
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo 192–0397, Japan
| | - Hiroki Maeda
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo 192–0397, Japan
| | - Kentaro Tamura
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606–8502, Japan
| | - Ikuko Hara-Nishimura
- Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606–8502, Japan
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Tokyo 192–0397, Japan
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Kurihara D, Hamamura Y, Higashiyama T. Live-cell analysis of plant reproduction: Live-cell imaging, optical manipulation, and advanced microscopy technologies. Dev Growth Differ 2013; 55:462-73. [DOI: 10.1111/dgd.12040] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 12/29/2012] [Accepted: 01/04/2013] [Indexed: 02/05/2023]
Affiliation(s)
| | - Yuki Hamamura
- Division of Biological Science; Graduate School of Science; Furo-cho, Chikusa-ku; Nagoya; Aichi; 464-8602; Japan
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Ueda M, Laux T. The origin of the plant body axis. CURRENT OPINION IN PLANT BIOLOGY 2012; 15:578-84. [PMID: 22921364 DOI: 10.1016/j.pbi.2012.08.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2012] [Revised: 08/01/2012] [Accepted: 08/07/2012] [Indexed: 05/11/2023]
Abstract
During embryogenesis, the basic body plan of an organism develops from a unicellular zygote. In most flowering plants, the polar zygote divides asymmetrically, making visible the apical-basal axis in the early embryo. The molecular mechanisms governing how the zygote polarizes and how this polarity is linked to embryo axis formation have been obscure, mainly owing to the difficulties to access the zygote that is deeply embedded in the maternal tissue. In this review, we summarize recent findings identifying key regulators in Arabidopsis and developing novel approaches in various plant species, which altogether set the stage for unraveling embryo axis formation.
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Affiliation(s)
- Minako Ueda
- Laboratory of Plant Growth Regulation, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Takayamacho 8916-5, Ikoma, Nara 630-0192, Japan.
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Okamoto T. In vitro fertilization with rice gametes: production of zygotes and zygote and embryo culture. Methods Mol Biol 2011; 710:17-27. [PMID: 21207258 DOI: 10.1007/978-1-61737-988-8_2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
In vitro fertilization (IVF) systems using isolated male and female gametes have been utilized to dissect fertilization-induced events in angiosperms, such as egg activation, zygote development, and early embryogenesis, since the female gametophytes of plants are deeply embedded within ovaries. A rice IVF system was established to take advantage of the abundant resources stemming from rice research for investigations into the mechanisms of fertilization and early embryogenesis. Fusion of gametes can be performed using electrofusion and the fusion product, a zygote, forms a cell wall and an additional nucleolus. The zygote divides into an asymmetric two-celled embryo and develops into an early globular embryo, as in planta. The embryo further develops into irregularly shaped cell masses and fertile plants can be regenerated from the cell masses. This rice IVF system is a powerful tool for studying the molecular mechanisms involved in the early embryogenesis of angiosperms and for making new cultivars.
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Affiliation(s)
- Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan.
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Okamoto T. Gamete fusion site on the egg cell and autonomous establishment of cell polarity in the zygote. PLANT SIGNALING & BEHAVIOR 2010; 5:1464-7. [PMID: 21051936 PMCID: PMC3115256 DOI: 10.4161/psb.5.11.13468] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Gamete fusion activates the egg in animals and plants, and the gamete fusion site on the zygote might provide a possible cue for zygotic development and/or embryonic patterning. In angiosperms, a zygote generally divides into a two-celled proembryo consisting of an apical and a basal cell with different cell fates. This is a putative step in the formation of the apical-basal axis of the proembryo. We observed the positional relationship between the gamete fusion site and the division plane formed by zygotic cleavage using an in vitro fertilization system with rice gametes. There was no relationship between the gamete fusion site and the division plane leading to the two-celled proembryo. Thus, the gamete fusion site on the rice zygote does not appear to function as a determinant for positioning the zygote division plane, and the zygote apparently possesses autonomous potential to establish cell polarity along the apical-basal axis for its first cleavage.
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Affiliation(s)
- Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Tokyo, Japan.
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Nakajima K, Uchiumi T, Okamoto T. Positional relationship between the gamete fusion site and the first division plane in the rice zygote. JOURNAL OF EXPERIMENTAL BOTANY 2010; 61:3101-5. [PMID: 20462944 PMCID: PMC2892148 DOI: 10.1093/jxb/erq131] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 04/26/2010] [Accepted: 04/27/2010] [Indexed: 05/20/2023]
Abstract
In angiosperms, a zygote generally divides into a two-celled proembryo consisting of an apical and a basal cell that possess different cell fates. This first division of the zygote is a putative step in the formation of the apical-basal axis of the proembryo. The gamete fusion activates the egg, and the gamete fusion site on the zygote has been reported to provide a possible cue for subsequent zygotic development and/or embryonic patterning in animals and plants. In this study, the gamete fusion site on the rice zygote was labelled by in vitro fertilization of a rice egg cell with a fluorescence-stained sperm cell. The positional relationship between the gamete fusion site and the division plane formed by zygotic cleavage was monitored using a fixed culture of the fusion site-labelled zygote until the two-celled proembryo stage. The results indicate that gamete fusion sites exist on two-celled proembryos with no relation to the position of the first division plane, and that the gamete fusion site on the rice zygote does not function as a determinant for positioning the zygote division plane.
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Affiliation(s)
| | | | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, 1-1 Minami-osawa Hachioji, Tokyo 192-0397, Japan
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50
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Sato A, Toyooka K, Okamoto T. Asymmetric cell division of rice zygotes located in embryo sac and produced by in vitro fertilization. ACTA ACUST UNITED AC 2010; 23:211-7. [DOI: 10.1007/s00497-009-0129-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Accepted: 12/11/2009] [Indexed: 11/24/2022]
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