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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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Khurana R, Bhimrajka S, Sivakrishna Rao G, Verma V, Boora N, Gawande G, Kapoor M, Rao KV, Kapoor S. Characterization of Transcription Regulatory Domains of OsMADS29: Identification of Proximal Auxin-Responsive Domains and a Strong Distal Negative Element. FRONTIERS IN PLANT SCIENCE 2022; 13:850956. [PMID: 35557721 PMCID: PMC9085466 DOI: 10.3389/fpls.2022.850956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/08/2022] [Accepted: 03/02/2022] [Indexed: 06/15/2023]
Abstract
OsMADS29 (M29) is a seed-specific MADS-box transcription factor involved in programmed cell death of nucellar tissue and maintaining auxin:cytokinin homeostasis. It affects embryo and endosperm development and starch filling during seed development in rice. Its expression seems to be tightly regulated by developmental, spatial, and temporal cues; however, cis- and trans-regulatory factors that affect its expression are largely unknown. In silico analysis of the 1.7 kb upstream regulatory region (URR) consisting of 1,290 bp promoter and 425 bp 5'-UTR regions revealed several auxin-responsive and seed-specific cis-regulatory elements distributed across the URR. In this study, the analysis of four URR deletions fused to a downstream β-glucuronidase (GUS) reporter in transgenic rice has revealed the presence of several proximal positive elements and a strong distal negative element (NE). The promoter regions containing auxin-responsive elements responded positively to the exogenous application of auxins to transgenic seedlings. The proximal positive elements are capable of driving reporter expression in both vegetative and reproductive tissues. In contrast, the NE strongly suppresses reporter gene expression in both vegetative and reproductive tissues. In a transient onion peel assay system, the NE could reduce the efficacy of a 2x CaMV 35S promoter by ∼90%. Our results indicate the existence of a complex array of positive and negative regulatory regions along with auxin-responsive elements guiding the development-dependent and spatial expression of M29.
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Affiliation(s)
- Ridhi Khurana
- Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, India
| | - Sanchi Bhimrajka
- Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, India
| | | | - Vibha Verma
- Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, India
| | - Neelima Boora
- Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, India
| | - Gautam Gawande
- Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, India
| | - Meenu Kapoor
- University School of Biotechnology, Guru Gobind Singh Indraprastha University, New Delhi, India
| | | | - Sanjay Kapoor
- Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, India
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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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Zhao P, Shi C, Wang L, Sun MX. The parental contributions to early plant embryogenesis and the concept of maternal-to-zygotic transition in plants. CURRENT OPINION IN PLANT BIOLOGY 2022; 65:102144. [PMID: 34823206 DOI: 10.1016/j.pbi.2021.102144] [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: 05/15/2021] [Revised: 10/20/2021] [Accepted: 10/21/2021] [Indexed: 06/13/2023]
Abstract
The maternal-to-zygotic transition (MZT) is a major developmental transition in the life cycles of animals. It consists of two associated processes: maternal transcript clearance and zygotic genome activation (ZGA). The concept of MZT has been controversially discussed in plants. In this short review, we summarize recent advances in understanding the timing of ZGA and the similarities and differences between ZGA in eudicots and monocots. We discuss the parental contributions to the transcriptome of the proembryo and parental control of early embryogenesis, and we examine distinct differences in the ZGA between animals and plants, update relevant concepts on MZT, and highlight outstanding questions in this field.
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Affiliation(s)
- Peng Zhao
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China; Hubei Hongshan Laboratory, Wuhan, 430070, China
| | - Ce Shi
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Ling Wang
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China
| | - Meng-Xiang Sun
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan 430072, China.
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The Evolution and Expression Profiles of EC1 Gene Family during Development in Cotton. Genes (Basel) 2021; 12:genes12122001. [PMID: 34946950 PMCID: PMC8702097 DOI: 10.3390/genes12122001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Revised: 12/13/2021] [Accepted: 12/14/2021] [Indexed: 12/04/2022] Open
Abstract
Fertilization is essential to sexual reproduction of flowering plants. EC1 (EGG CELL 1) proteins have a conserved cysteine spacer characteristic and play a crucial role in double fertilization process in many plant species. However, to date, the role of EC1 gene family in cotton is fully unknown. Hence, detailed bioinformatics analysis was explored to elucidate the biological mechanisms of EC1 gene family in cotton. In this study, we identified 66 genes in 10 plant species in which a total of 39 EC1 genes were detected from cotton genome. Phylogenetic analysis clustered the identified EC1 genes into three families (I-III) and all of them contain Prolamin-like domains. A good collinearity was observed in the synteny analysis of the orthologs from cotton genomes. Whole-genome duplication was determined to be one of the major impetuses for the expansion of the EC1 gene family during the process of evolution. qRT-PCR analysis showed that EC1 genes were highly expressed in reproductive tissues under multiple stresses, signifying their potential role in enhancing stress tolerance or responses. Additionally, gene interaction networks showed that EC1 genes may be involved in cell stress and response transcriptional regulator in the synergid cells and activate the expression of genes required for pollen tube guidance. Our results provide novel functional insights into the evolution and functional elucidation of EC1 gene family in cotton.
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Maryenti T, Ishii T, Okamoto T. Development and regeneration of wheat-rice hybrid zygotes produced by in vitro fertilization system. THE NEW PHYTOLOGIST 2021; 232:2369-2383. [PMID: 34545570 PMCID: PMC9293317 DOI: 10.1111/nph.17747] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2021] [Accepted: 09/14/2021] [Indexed: 05/20/2023]
Abstract
Hybridization plays a decisive role in the evolution and diversification of angiosperms. However, the mechanisms of wide hybridization remain open because pre- and post-fertilization barriers limit the production and development of inter-subfamily/intergeneric zygotes, respectively. We examined hybridization between wheat and rice using an in vitro fertilization (IVF) system to bypass these barriers. Several gamete combinations of allopolyploid wheat-rice hybrid zygotes were successfully produced, and the developmental profiles of hybrid zygotes were analyzed. Hybrid zygotes derived from one rice egg cell and one wheat sperm cell ceased at the multicellular embryo-like structure stage. This developmental barrier was overcome by adding one wheat egg cell to the wheat-rice hybrid zygote. In the reciprocal combination, one wheat egg and one rice sperm cell, the resulting hybrid zygotes failed to divide. However, doubling the dosage of rice sperm cell allowed the hybrid zygotes to develop into plantlets. Rice chromosomes appeared to be progressively eliminated during the early developmental stage of these hybrid embryos, and c. 20% of regenerated plants showed abnormal morphology. These results suggest that hybrid breakdown can be overcome through optimization of gamete combinations, and the present hybrid will provide a new horizon for utilization of inter-subfamily genetic resources.
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Affiliation(s)
- Tety Maryenti
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawa 1‐1Hachioji, Tokyo192‐0397Japan
| | - Takayoshi Ishii
- Arid Land Research Center (ALRC)Tottori University1390 HamasakaTottori680‐0001Japan
| | - Takashi Okamoto
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawa 1‐1Hachioji, Tokyo192‐0397Japan
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Rattanawong K, Koiso N, Toda E, Kinoshita A, Tanaka M, Tsuji H, Okamoto T. Regulatory functions of ROS dynamics via glutathione metabolism and glutathione peroxidase activity in developing rice zygote. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 108:1097-1115. [PMID: 34538012 PMCID: PMC9293154 DOI: 10.1111/tpj.15497] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 08/24/2021] [Accepted: 08/25/2021] [Indexed: 06/01/2023]
Abstract
Reactive oxygen species (ROS) play essential roles in plant development and environmental stress responses. In this study, ROS dynamics, the glutathione redox status, the expression and subcellular localization of glutathione peroxidases (GPXs), and the effects of inhibitors of ROS-mediated metabolism were investigated along with fertilization and early zygotic embryogenesis in rice (Oryza sativa). Zygotes and early embryos exhibited developmental arrest upon inhibition of ROS production. Egg cells accumulated high ROS levels, and, after fertilization, intracellular ROS levels progressively declined in zygotes in which de novo expression of GPX1 and 3 was observed through upregulation of the genes. In addition to inhibition of GPX activity, depletion of glutathione impeded early embryonic development and led to failure of the zygote to appropriately decrease H2 O2 levels. Moreover, through monitoring of the glutathione redox status, the developing zygotes exhibited a progressive glutathione oxidation, which became extremely delayed under inhibited GPX activity. Our results provide insights into the importance of ROS dynamics, GPX antioxidant activity, and glutathione redox metabolism during zygotic/embryonic development.
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Affiliation(s)
- Kasidit Rattanawong
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawaHachioji, TokyoJapan
| | - Narumi Koiso
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawaHachioji, TokyoJapan
| | - Erika Toda
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawaHachioji, TokyoJapan
| | - Atsuko Kinoshita
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawaHachioji, TokyoJapan
| | - Mari Tanaka
- Kihara Institute for Biological ResearchYokohama City UniversityMaiokachoTotsuka‐kuYokohamaKanagawaJapan
| | - Hiroyuki Tsuji
- Kihara Institute for Biological ResearchYokohama City UniversityMaiokachoTotsuka‐kuYokohamaKanagawaJapan
| | - Takashi Okamoto
- Department of Biological SciencesTokyo Metropolitan UniversityMinami‐osawaHachioji, TokyoJapan
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8
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Ke Y, Podio M, Conner J, Ozias-Akins P. Single-cell transcriptome profiling of buffelgrass (Cenchrus ciliaris) eggs unveils apomictic parthenogenesis signatures. Sci Rep 2021; 11:9880. [PMID: 33972603 PMCID: PMC8110759 DOI: 10.1038/s41598-021-89170-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 04/15/2021] [Indexed: 12/04/2022] Open
Abstract
Apomixis, a type of asexual reproduction in angiosperms, results in progenies that are genetically identical to the mother plant. It is a highly desirable trait in agriculture due to its potential to preserve heterosis of F1 hybrids through subsequent generations. However, no major crops are apomictic. Deciphering mechanisms underlying apomixis becomes one of the alternatives to engineer self-reproducing capability into major crops. Parthenogenesis, a major component of apomixis, commonly described as the ability to initiate embryo formation from the egg cell without fertilization, also can be valuable in plant breeding for doubled haploid production. A deeper understanding of transcriptional differences between parthenogenetic and sexual or non-parthenogenetic eggs can assist with pathway engineering. By conducting laser capture microdissection-based RNA-seq on sexual and parthenogenetic egg cells on the day of anthesis, a de novo transcriptome for the Cenchrus ciliaris egg cells was created, transcriptional profiles that distinguish the parthenogenetic egg from its sexual counterpart were identified, and functional roles for a few transcription factors in promoting natural parthenogenesis were suggested. These transcriptome data expand upon previous gene expression studies and will be a resource for future research on the transcriptome of egg cells in parthenogenetic and sexual genotypes.
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Affiliation(s)
- Yuji Ke
- Institute of Plant Breeding, Genetics and Genomics, University of Georgia, Tifton, GA, 31793, USA
| | - Maricel Podio
- Department of Horticulture, University of Georgia, Tifton, GA, 31793, USA
| | - Joann Conner
- Institute of Plant Breeding, Genetics and Genomics, University of Georgia, Tifton, GA, 31793, USA.,Department of Horticulture, University of Georgia, Tifton, GA, 31793, USA
| | - Peggy Ozias-Akins
- Institute of Plant Breeding, Genetics and Genomics, University of Georgia, Tifton, GA, 31793, USA. .,Department of Horticulture, University of Georgia, Tifton, GA, 31793, USA.
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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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Abstract
Carbohydrates (sugars) are an essential energy-source for all life forms. They take a significant share of our daily consumption and are used for biofuel production as well. However, sugarcane and sugar beet are the only two crop plants which are used to produce sugar in significant amounts. Here, we have discovered and fine-tuned a phenomenon in rice which leads them to produce sugary-grain. We knocked-out GCS1 genes in rice by using CRISPR technology, which led to fertilization failure and pollen tube-dependent ovule enlargement morphology (POEM) phenomenon. Apparently, the POEMed-like rice ovule ('endosperm-focused') can grow near-normal seed-size unlike earlier observations in Arabidopsis in which gcs1 ovules ('embryo-focused') were aborted quite early. The POEMed-like rice ovules contained 10-20% sugar, with extremely high sucrose content (98%). Trancriptomic analysis revealed that the osgcs1 ovules had downregulation of starch biosynthetic genes, which would otherwise have converted sucrose to starch. Overall, this study shows that pollen tube content release is sufficient to trigger sucrose unloading at rice ovules. However, successful fertilization is indispensable to trigger sucrose-starch conversion. These findings are expected to pave the way for developing novel sugar producing crops suited for diverse climatic regions.
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Abstract
In higher plants, fertilization induces many structural and physiological changes in the fertilized egg that reflect the transition from the haploid female gamete to the diploid zygote - the first cell of the sporophyte. After fusion of the egg nucleus with the sperm nucleus, many molecular changes occur in the zygote during the process of zygote activation during embryogenesis. The zygote originates from the egg, from which some pre-stored translation initiation factors transfer into the zygote and function during zygote activation. This indicates that the control of zygote activation is pre-set in the egg. After the egg and sperm nuclei fuse, gene expression is activated in the zygote, and paternal and maternal gene expression patterns are displayed. This highlights the diversity of zygotic genome activation in higher plants. In addition to new gene expression in the zygote, some genes show quantitative changes in expression. The asymmetrical division of the zygote produces an apical cell and a basal cell that have different destinies during plant reconstruction; these destinies are determined in the zygote. This review describes significant advances in research on the mechanisms controlling zygote activation in higher plants.
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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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Kimata Y, Ueda M. Intracellular dynamics and transcriptional regulations in plant zygotes: a case study of Arabidopsis. PLANT REPRODUCTION 2020; 33:89-96. [PMID: 32322957 DOI: 10.1007/s00497-020-00389-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Accepted: 04/09/2020] [Indexed: 06/11/2023]
Abstract
Recent understandings ofArabidopsiszygote. Body axis formation is essential for the proper development of multicellular organisms. The apical-basal axis in Arabidopsis thaliana is determined by the asymmetric division of the zygote, following its cellular polarization. However, the regulatory mechanism of zygote polarization is unclear due to technical issues. The zygote is located deep in the seed (ovule) in flowers, which prevents the living dynamics of zygotes from being observed. In addition, elucidation of molecular pathways by conventional forward genetic screens was not enough because of high gene redundancy in early development. Here, we present a review introducing two new methods, which have been developed to overcome these problems. Method 1: the two-photon live-cell imaging method provides a new system to visualize the dynamics of intracellular structures in Arabidopsis zygotes, such as cytoskeletons and vacuoles. Microtubules form transverse rings and control zygote elongation, while vacuoles dynamically change their shapes along longitudinal actin filaments and support polar nuclear migration. Method 2: the transcriptome method uses isolated Arabidopsis zygotes and egg cells to reveal the gene expression profiles before and after fertilization. This approach revealed that de novo transcription occurs extensively and immediately after fertilization. Moreover, inhibition of the de novo transcription was shown to sufficiently block the zygotic division, thus indicating a strong possibility that yet unidentified zygote regulators can be found using this transcriptome approach. These new strategies in Arabidopsis will help to further our understanding of the fundamental principles regarding the proper formation of plant bodies from unicellular zygotes.
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Affiliation(s)
- Yusuke Kimata
- Institute of Transformative Bio-Molecules (ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601, Japan
| | - Minako Ueda
- Institute of Transformative Bio-Molecules (ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601, Japan.
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8602, Japan.
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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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Abstract
Zygotic embryogenesis is one of key processes for fertile seed development and therefore has gained great attention for decades in the field of plant developmental biology. However, this process is deeply embedded in the maternal tissues. The inaccessibility of tiny early embryos has greatly hindered the study of early embryogenesis, especially limits direct observation and accurate omics investigations. In order to investigate the molecular mechanism regulating embryo development with modern technologies, it is necessary to develop a reliable method to isolate living embryos at different stages. For this purpose, plant scientists have been trying to develop different methods for isolating zygotes and early embryos in different plants such as maize, wheat, rice, and tobacco during past decades. Nicotiana tabacum has long been considered as an ideal model eudicot for the study of embryogenesis, which displays a traceable and predictable cell division pattern, spanning from the first zygotic division to the mature embryo formation. Here, we provide a detailed protocol for isolating living embryos from zygote to cotyledon embryo. Isolated living zygotes and early embryos could be used for several important studies such as cell type-specific transcriptome construction and clear GFP observation.
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Affiliation(s)
- Peng Zhao
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China.
| | - Xuemei Zhou
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Ce Shi
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
| | - Meng-Xiang Sun
- State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, China
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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] [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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17
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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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18
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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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19
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Ueda M, Berger F. New cues for body axis formation in plant embryos. CURRENT OPINION IN PLANT BIOLOGY 2019; 47:16-21. [PMID: 30223185 DOI: 10.1016/j.pbi.2018.08.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 08/28/2018] [Accepted: 08/28/2018] [Indexed: 06/08/2023]
Abstract
Plant embryogenesis initiates with the fusion of sperm and egg cell, and completes the generation of the basic outline of the future plant. Here, we summarize the recent findings about the signaling cascade triggering the zygotic transcription, and the intracellular events and regulatory factors involved in the formation of the two major body axes. We highlight the lack of systematic de novo transcriptional activation in the zygote, and emphasize the importance of cytoskeletal reorganization to polarize the zygote and control the first asymmetric division that establishes the apical-basal axis. Finally, the limited knowledge of mechanisms that control the cell divisions separating the inner and outer cell layers is summarized and we propose approaches to enhance our understanding of basic principles of plant embryogenesis.
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Affiliation(s)
- Minako Ueda
- Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan; Institute of Transformative Bio-Molecules (ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan.
| | - Frédéric Berger
- Gregor Mendel Institute (GMI), Austrian Academy of Sciences, Vienna Biocenter (VBC), Dr. Bohr-Gasse 3, 1030 Vienna, Austria
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20
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Fehér A. Callus, Dedifferentiation, Totipotency, Somatic Embryogenesis: What These Terms Mean in the Era of Molecular Plant Biology? FRONTIERS IN PLANT SCIENCE 2019; 10:536. [PMID: 31134106 PMCID: PMC6524723 DOI: 10.3389/fpls.2019.00536] [Citation(s) in RCA: 112] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Accepted: 04/08/2019] [Indexed: 05/18/2023]
Abstract
Recent findings call for the critical overview of some incorrectly used plant cell and tissue culture terminology such as dedifferentiation, callus, totipotency, and somatic embryogenesis. Plant cell and tissue culture methods are efficient means to preserve and propagate genotypes with superior germplasm as well as to increase genetic variability for breading. Besides, they are useful research tools and objects of plant developmental biology. The history of plant cell and tissue culture dates back to more than a century. Its basic methodology and terminology were formulated preceding modern plant biology. Recent progress in molecular and cell biology techniques allowed unprecedented insights into the underlying processes of plant cell/tissue culture and regeneration. The main aim of this review is to provide a theoretical framework supported by recent experimental findings to reconsider certain historical, even dogmatic, statements widely used by plant scientists and teachers such as "plant cells are totipotent" or "callus is a mass of dedifferentiated cells," or "somatic embryos have a single cell origin." These statements are based on a confused terminology. Clarification of it might help to avoid further misunderstanding and to overcome potential "terminology-raised" barriers in plant research.
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Affiliation(s)
- Attila Fehér
- Department of Plant Biology, University of Szeged, Szeged, Hungary
- Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
- *Correspondence: Attila Fehér, ;
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21
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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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22
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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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23
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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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24
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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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25
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Zhao P, Begcy K, Dresselhaus T, Sun MX. Does Early Embryogenesis in Eudicots and Monocots Involve the Same Mechanism and Molecular Players? PLANT PHYSIOLOGY 2017; 173:130-142. [PMID: 27909044 PMCID: PMC5210740 DOI: 10.1104/pp.16.01406] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Accepted: 11/30/2016] [Indexed: 05/18/2023]
Abstract
A comparison of eudicot and monocot model plants explores recent advances and open questions on gene regulatory networks during zygote development, parental influences on early embryogenesis, zygotic genome activation, and cell fate determination.
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Affiliation(s)
- Peng Zhao
- College of Life Sciences, State Key Laboratory of Hybrid Rice, Wuhan University, Wuhan 430072, China (P.Z., M.-X.S.); and
- Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, 93053 Regensburg, Germany (K.B., T.D.)
| | - Kevin Begcy
- College of Life Sciences, State Key Laboratory of Hybrid Rice, Wuhan University, Wuhan 430072, China (P.Z., M.-X.S.); and
- Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, 93053 Regensburg, Germany (K.B., T.D.)
| | - Thomas Dresselhaus
- College of Life Sciences, State Key Laboratory of Hybrid Rice, Wuhan University, Wuhan 430072, China (P.Z., M.-X.S.); and
- Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, 93053 Regensburg, Germany (K.B., T.D.)
| | - Meng-Xiang Sun
- College of Life Sciences, State Key Laboratory of Hybrid Rice, Wuhan University, Wuhan 430072, China (P.Z., M.-X.S.); and
- Cell Biology and Plant Biochemistry, Biochemie-Zentrum Regensburg, University of Regensburg, 93053 Regensburg, Germany (K.B., T.D.)
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26
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DNA demethylation is initiated in the central cells of Arabidopsis and rice. Proc Natl Acad Sci U S A 2016; 113:15138-15143. [PMID: 27956642 DOI: 10.1073/pnas.1619047114] [Citation(s) in RCA: 129] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Cytosine methylation is a DNA modification with important regulatory functions in eukaryotes. In flowering plants, sexual reproduction is accompanied by extensive DNA demethylation, which is required for proper gene expression in the endosperm, a nutritive extraembryonic seed tissue. Endosperm arises from a fusion of a sperm cell carried in the pollen and a female central cell. Endosperm DNA demethylation is observed specifically on the chromosomes inherited from the central cell in Arabidopsis thaliana, rice, and maize, and requires the DEMETER DNA demethylase in Arabidopsis DEMETER is expressed in the central cell before fertilization, suggesting that endosperm demethylation patterns are inherited from the central cell. Down-regulation of the MET1 DNA methyltransferase has also been proposed to contribute to central cell demethylation. However, with the exception of three maize genes, central cell DNA methylation has not been directly measured, leaving the origin and mechanism of endosperm demethylation uncertain. Here, we report genome-wide analysis of DNA methylation in the central cells of Arabidopsis and rice-species that diverged 150 million years ago-as well as in rice egg cells. We find that DNA demethylation in both species is initiated in central cells, which requires DEMETER in Arabidopsis However, we do not observe a global reduction of CG methylation that would be indicative of lowered MET1 activity; on the contrary, CG methylation efficiency is elevated in female gametes compared with nonsexual tissues. Our results demonstrate that locus-specific, active DNA demethylation in the central cell is the origin of maternal chromosome hypomethylation in the endosperm.
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27
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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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28
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Toda E, Ohnishi Y, Okamoto T. Development of Polyspermic Rice Zygotes. PLANT PHYSIOLOGY 2016; 171:206-14. [PMID: 26945052 PMCID: PMC4854695 DOI: 10.1104/pp.15.01953] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2015] [Accepted: 03/02/2016] [Indexed: 05/03/2023]
Abstract
Fertilization is a general feature of eukaryotic uni- and multicellular organisms to restore a diploid genome from female and male gamete haploid genomes. In most animals and fucoid algae, polyspermy block occurs at the plasmogamy step. Because the polyspermy barrier in animals and in fucoid algae is incomplete, polyspermic zygotes are generated by multiple fertilization events. However, these polyspermic zygotes with extra centrioles from multiple sperms show aberrant nuclear and cell division. In angiosperms, polyspermy block functions in the egg cell and the central cell to promote faithful double fertilization, although the mechanism of polyspermy block remains unclear. In contrast to the case in animals and fucoid algae, polyspermic zygotes formed in angiosperms are not expected to die because angiosperms lack centrosomes. However, there have been no reports on the developmental profiles of polyspermic zygotes at cellular level in angiosperms. In this study, we produced polyspermic rice zygotes by electric fusion of an egg cell with two sperm cells, and monitored their developmental profiles. Two sperm nuclei and an egg nucleus fused into a zygotic nucleus, and the triploid zygote divided into a two-celled embryo via mitotic division with a typical bipolar microtubule spindle, as observed during mitosis of a diploid zygote. The two-celled proembryos further developed and regenerated into triploid plants. These findings suggest that polyspermic plant zygotes have the potential to form triploid embryos. Polyspermy in angiosperms might be a pathway for the formation of triploid plants, which can contribute significantly to the formation of autopolyploids.
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Affiliation(s)
- Erika Toda
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo 192-0397, Japan (E.T., Y.O., T.O.)
| | - Yukinosuke Ohnishi
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo 192-0397, Japan (E.T., Y.O., T.O.)
| | - Takashi Okamoto
- Department of Biological Sciences, Tokyo Metropolitan University, Minami-osawa, Hachioji, Tokyo 192-0397, Japan (E.T., Y.O., T.O.)
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29
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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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30
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Gene Expression Profiles in Rice Developing Ovules Provided Evidence for the Role of Sporophytic Tissue in Female Gametophyte Development. PLoS One 2015; 10:e0141613. [PMID: 26506227 PMCID: PMC4624635 DOI: 10.1371/journal.pone.0141613] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 10/09/2015] [Indexed: 12/21/2022] Open
Abstract
The development of ovule in rice (Oryza sativa) is vital during its life cycle. To gain more understanding of the molecular events associated with the ovule development, we used RNA sequencing approach to perform transcriptome-profiling analysis of the leaf and ovules at four developmental stages. In total, 25,401, 23,343, 23,647 and 23,806 genes were identified from the four developmental stages of the ovule, respectively. We identified a number of differently expressed genes (DEGs) from three adjacent stage comparisons, which may play crucial roles in ovule development. The DEGs were then conducted functional annotations and Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses. Genes related to cellular component biogenesis, membrane-bounded organelles and reproductive regulation were identified to be highly expressed during the ovule development. Different expression levels of auxin-related and cytokinin-related genes were also identified at various stages, providing evidence for the role of sporophytic ovule tissue in female gametophyte development from the aspect of gene expression. Generally, an overall transcriptome analysis for rice ovule development has been conducted. These results increased our knowledge of the complex molecular and cellular events that occur during the development of rice ovule and provided foundation for further studies on rice ovule development.
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31
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Baroux C, Grossniklaus U. The Maternal-to-Zygotic Transition in Flowering Plants: Evidence, Mechanisms, and Plasticity. Curr Top Dev Biol 2015; 113:351-71. [PMID: 26358878 DOI: 10.1016/bs.ctdb.2015.06.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
The maternal-to-zygotic transition (MZT) defines a developmental phase during which the embryo progressively emancipates itself from a developmental control relying largely on maternal information. The MZT is a functional readout of two processes: the clearance of maternally derived information and the de novo expression of the inherited, parental alleles enabled by zygotic genome activation (ZGA). In plants, for many years the debate about whether the MZT exists at all focused on the ZGA alone. However, several recent studies provide evidence for a progressive alleviation of the maternal control over embryogenesis that is correlated with a gradual ZGA, a process that is itself maternally controlled. Yet, several examples of zygotic genes that are expressed and/or functionally required early in embryogenesis demonstrate a certain flexibility in the dynamics and kinetics of the MZT among plant species and also intraspecific hybrids.
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Affiliation(s)
- Célia Baroux
- Institute of Plant Biology & Zurich-Basel Plant Science Center, University of Zurich, Zurich, Switzerland
| | - Ueli Grossniklaus
- Institute of Plant Biology & Zurich-Basel Plant Science Center, University of Zurich, Zurich, Switzerland.
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32
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Schmidt A, Schmid MW, Grossniklaus U. Plant germline formation: common concepts and developmental flexibility in sexual and asexual reproduction. Development 2015; 142:229-41. [PMID: 25564620 DOI: 10.1242/dev.102103] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The life cycle of flowering plants alternates between two heteromorphic generations: a diploid sporophytic generation and a haploid gametophytic generation. During the development of the plant reproductive lineages - the germlines - typically, single sporophytic (somatic) cells in the flower become committed to undergo meiosis. The resulting spores subsequently develop into highly polarized and differentiated haploid gametophytes that harbour the gametes. Recent studies have provided insights into the genetic basis and regulatory programs underlying cell specification and the acquisition of reproductive fate during both sexual reproduction and asexual (apomictic) reproduction. As we review here, these recent advances emphasize the importance of transcriptional, translational and post-transcriptional regulation, and the role of epigenetic regulatory pathways and hormonal activity.
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Affiliation(s)
- Anja Schmidt
- Institute of Plant Biology and Zürich-Basel Plant Science Centre, University of Zürich, Zollikerstrasse 107, Zürich CH-8008, Switzerland
| | - Marc W Schmid
- Institute of Plant Biology and Zürich-Basel Plant Science Centre, University of Zürich, Zollikerstrasse 107, Zürich CH-8008, Switzerland
| | - Ueli Grossniklaus
- Institute of Plant Biology and Zürich-Basel Plant Science Centre, University of Zürich, Zollikerstrasse 107, Zürich CH-8008, Switzerland
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33
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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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34
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Russell SD, Jones DS. The male germline of angiosperms: repertoire of an inconspicuous but important cell lineage. FRONTIERS IN PLANT SCIENCE 2015; 6:173. [PMID: 25852722 PMCID: PMC4367165 DOI: 10.3389/fpls.2015.00173] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Accepted: 03/03/2015] [Indexed: 05/03/2023]
Abstract
The male germline of flowering plants constitutes a specialized lineage of diminutive cells initiated by an asymmetric division of the initial microspore cell that sequesters the generative cell from the pollen vegetative cell. The generative cell subsequently divides to form the two male gametes (non-motile sperm cells) that fuse with the two female gametophyte target cells (egg and central cells) to form the zygote and endosperm. Although these male gametes can be as little as 1/800th of the volume of their female counterpart, they encode a highly distinctive and rich transcriptome, translate proteins, and display a novel suite of gamete-distinctive control elements that create a unique chromatin environment in the male lineage. Sperm-expressed transcripts also include a high proportion of transposable element-related sequences that may be targets of non-coding RNA including miRNA and silencing elements from peripheral cells. The number of sperm-encoded transcripts is somewhat fewer than the number present in the egg cell, but are remarkably distinct compared to other cell types according to principal component and other analyses. The molecular role of the male germ lineage cells is just beginning to be understood and appears more complex than originally anticipated.
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Affiliation(s)
- Scott D. Russell
- *Correspondence: Scott D. Russell, Department of Microbiology and Plant Biology, University of Oklahoma, Norman, 770 Van Vleet Oval, OK 73019, USA
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35
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Podio M, Cáceres ME, Samoluk SS, Seijo JG, Pessino SC, Ortiz JPA, Pupilli F. A methylation status analysis of the apomixis-specific region in Paspalum spp. suggests an epigenetic control of parthenogenesis. JOURNAL OF EXPERIMENTAL BOTANY 2014; 65:6411-24. [PMID: 25180110 DOI: 10.1093/jxb/eru354] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Apomixis, a clonal plant reproduction by seeds, is controlled in Paspalum spp. by a single locus which is blocked in terms of recombination. Partial sequence analysis of the apomixis locus revealed structural features of heterochromatin, namely the presence of repetitive elements, gene degeneration, and de-regulation. To test the epigenetic control of apomixis, a study on the distribution of cytosine methylation at the apomixis locus and the effect of artificial DNA demethylation on the mode of reproduction was undertaken in two apomictic Paspalum species. The 5-methylcytosine distribution in the apomixis-controlling genomic region was studied in P. simplex by methylation-sensitive restriction fragment length polymorphism (RFLP) analysis and in P. notatum by fluorescene in situ hybridization (FISH). The effect of DNA demethylation was studied on the mode of reproduction of P. simplex by progeny test analysis of apomictic plants treated with the demethylating agent 5'-azacytidine. A high level of cytosine methylation was detected at the apomixis-controlling genomic region in both species. By analysing a total of 374 open pollination progeny, it was found that artificial demethylation had little or no effect on apospory, whereas it induced a significant depression of parthenogenesis. The results suggested that factors controlling repression of parthenogenesis might be inactivated in apomictic Paspalum by DNA methylation.
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Affiliation(s)
- Maricel Podio
- Laboratorio de Biología Molecular, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, Campo Experimental Villarino s/n CC 14 (S2125 ZAA), Zavalla, Santa Fe, Argentina Instituto de Botánica del Nordeste (IBONE-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste, Sargento Cabral 2131, 3400 Corrientes, Argentina
| | - Maria E Cáceres
- CNR-Istituto di Bioscienze e Biorisorse, Research Division: Perugia, Via della Madonna alta 130, I-06128 Perugia, Italy
| | - Sergio S Samoluk
- Instituto de Botánica del Nordeste (IBONE-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste, Sargento Cabral 2131, 3400 Corrientes, Argentina
| | - José G Seijo
- Instituto de Botánica del Nordeste (IBONE-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste, Sargento Cabral 2131, 3400 Corrientes, Argentina
| | - Silvina C Pessino
- Laboratorio de Biología Molecular, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, Campo Experimental Villarino s/n CC 14 (S2125 ZAA), Zavalla, Santa Fe, Argentina
| | - Juan Pablo A Ortiz
- Laboratorio de Biología Molecular, Facultad de Ciencias Agrarias, Universidad Nacional de Rosario, Campo Experimental Villarino s/n CC 14 (S2125 ZAA), Zavalla, Santa Fe, Argentina Instituto de Botánica del Nordeste (IBONE-CONICET), Facultad de Ciencias Agrarias, Universidad Nacional del Nordeste, Sargento Cabral 2131, 3400 Corrientes, Argentina
| | - Fulvio Pupilli
- CNR-Istituto di Bioscienze e Biorisorse, Research Division: Perugia, Via della Madonna alta 130, I-06128 Perugia, Italy
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36
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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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37
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Chettoor AM, Givan SA, Cole RA, Coker CT, Unger-Wallace E, Vejlupkova Z, Vollbrecht E, Fowler JE, Evans MM. Discovery of novel transcripts and gametophytic functions via RNA-seq analysis of maize gametophytic transcriptomes. Genome Biol 2014; 15:414. [PMID: 25084966 PMCID: PMC4309534 DOI: 10.1186/s13059-014-0414-2] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 07/15/2014] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Plant gametophytes play central roles in sexual reproduction. A hallmark of the plant life cycle is that gene expression is required in the haploid gametophytes. Consequently, many mutant phenotypes are expressed in this phase. RESULTS We perform a quantitative RNA-seq analysis of embryo sacs, comparator ovules with the embryo sacs removed, mature pollen, and seedlings to assist the identification of gametophyte functions in maize. Expression levels were determined for annotated genes in both gametophytes, and novel transcripts were identified from de novo assembly of RNA-seq reads. Transposon-related transcripts are present in high levels in both gametophytes, suggesting a connection between gamete production and transposon expression in maize not previously identified in any female gametophytes. Two classes of small signaling proteins and several transcription factor gene families are enriched in gametophyte transcriptomes. Expression patterns of maize genes with duplicates in subgenome 1 and subgenome 2 indicate that pollen-expressed genes in subgenome 2 are retained at a higher rate than subgenome 2 genes with other expression patterns. Analysis of available insertion mutant collections shows a statistically significant deficit in insertions in gametophyte-expressed genes. CONCLUSIONS This analysis, the first RNA-seq study to compare both gametophytes in a monocot, identifies maize gametophyte functions, gametophyte expression of transposon-related sequences, and unannotated, novel transcripts. Reduced recovery of mutations in gametophyte-expressed genes is supporting evidence for their function in the gametophytes. Expression patterns of extant, duplicated maize genes reveals that selective pressures based on male gametophytic function have likely had a disproportionate effect on plant genomes.
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38
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Luo A, Shi C, Zhang L, Sun MX. The expression and roles of parent-of-origin genes in early embryogenesis of angiosperms. FRONTIERS IN PLANT SCIENCE 2014; 5:729. [PMID: 25566300 PMCID: PMC4267172 DOI: 10.3389/fpls.2014.00729] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 12/01/2014] [Indexed: 05/03/2023]
Abstract
Uniparental transcripts during embryogenesis may arise due to gamete delivery during fertilization or genomic imprinting. Such transcripts have been found in a number of plant species and appear critical for the early development of embryo or endosperm in seeds. Although the regulatory expression mechanism and function of these genes in embryogenesis require further elucidation, recent studies suggest stage-specific and highly dynamic features that might be essential for critical developmental events such as zygotic division and cell fate determination during embryogenesis. Here, we summarize the current work in this field and discuss future research directions.
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Affiliation(s)
- An Luo
- State Key Laboratory of Hybrid Rice, Department of Cell and Developmental Biology, College of Life Sciences, Wuhan UniversityWuhan, China
- College of Life Sciences, Yangtze UniversityJingzhou, China
| | - Ce Shi
- State Key Laboratory of Hybrid Rice, Department of Cell and Developmental Biology, College of Life Sciences, Wuhan UniversityWuhan, China
| | - Liyao Zhang
- State Key Laboratory of Hybrid Rice, Department of Cell and Developmental Biology, College of Life Sciences, Wuhan UniversityWuhan, China
| | - Meng-Xiang Sun
- State Key Laboratory of Hybrid Rice, Department of Cell and Developmental Biology, College of Life Sciences, Wuhan UniversityWuhan, China
- *Correspondence: Meng-Xiang Sun, State Key Laboratory of Hybrid Rice, Department of Cell and Developmental Biology, College of Life Sciences, Wuhan University, Wuhan 430072, Hubei, China e-mail:
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39
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Anderson SN, Johnson CS, Jones DS, Conrad LJ, Gou X, Russell SD, Sundaresan V. Transcriptomes of isolated Oryza sativa gametes characterized by deep sequencing: evidence for distinct sex-dependent chromatin and epigenetic states before fertilization. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 76:729-41. [PMID: 24215296 DOI: 10.1111/tpj.12336] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 09/12/2013] [Accepted: 09/19/2013] [Indexed: 05/19/2023]
Abstract
The formation of a zygote by the fusion of egg and sperm involves the two gametic transcriptomes. In flowering plants, the embryo sac embedded within the ovule contains the egg cell, whereas the pollen grain contains two sperm cells inside a supporting vegetative cell. The difficulties of collecting isolated gametes and consequent low recovery of RNA have restricted in-depth analysis of gametic transcriptomes in flowering plants. We isolated living egg cells, sperm cells and pollen vegetative cells from Oryza sativa (rice), and identified transcripts for approximately 36 000 genes by deep sequencing. The three transcriptomes are highly divergent, with about three-quarters of those genes differentially expressed in the different cell types. Distinctive expression profiles were observed for genes involved in chromatin conformation, including an unexpected expression in the sperm cell of genes associated with active chromatin. Furthermore, both the sperm cell and the pollen vegetative cell were deficient in expression of key RNAi components. Differences in gene expression were also observed for genes for hormonal signaling and cell cycle regulation. The egg cell and sperm cell transcriptomes reveal major differences in gene expression to be resolved in the zygote, including pathways affecting chromatin configuration, hormones and cell cycle. The sex-specific differences in the expression of RNAi components suggest that epigenetic silencing in the zygote might act predominantly through female-dependent pathways. More generally, this study provides a detailed gene expression landscape for flowering plant gametes, enabling the identification of specific gametic functions, and their contributions to zygote and seed development.
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Affiliation(s)
- Sarah N Anderson
- Department of Plant Biology, University of California, Davis, CA, 95616, USA
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40
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Leljak-Levanić D, Juranić M, Sprunck S. De novo zygotic transcription in wheat (Triticum aestivum L.) includes genes encoding small putative secreted peptides and a protein involved in proteasomal degradation. PLANT REPRODUCTION 2013; 26:267-85. [PMID: 23912470 DOI: 10.1007/s00497-013-0229-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 07/10/2013] [Indexed: 05/12/2023]
Abstract
Wheat is one of the world's most important crops, and increasing grain yield is a major challenge for the future. Still, our knowledge about the molecular machineries responsible for early post-fertilization events such as zygotic reprogramming, the initial cell-specification events during embryogenesis, and the intercellular communication between the early embryo and the developing endosperm is very limited. Here, we describe the identification of de novo transcribed genes in the wheat zygote. We used wheat ovaries of defined post-fertilization stages to isolate zygotes and early embryos, and identified genes that are specifically induced in these particular stages. Importantly, we observed that some of the zygotic-induced genes encode proteins with similarity to secreted signaling peptides such as TAPETUM DETERMINANT 1 and EGG APPARATUS 1, and to MATH-BTB proteins which are known substrate-binding adaptors for the Cullin3-based ubiquitin E3 ligase. This suggests that both cell-cell signaling and targeted proteasomal degradation may be important molecular events during zygote formation and the progression of early embryogenesis.
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Affiliation(s)
- Dunja Leljak-Levanić
- Department of Molecular Biology, Faculty of Science and Mathematics, University of Zagreb, Horvatovac 102a, 10000, Zagreb, Croatia
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