Research Laboratories
PLANT DEVELOPMENT AND PHYSIOLOGY (Takashi Okamoto, Toshiko Furukawa, Atsuko Kinoshita)
Research Overview
We are interested in the development and physiology of plants. We want to understand the principles of plant development and artificially recreate plant fertilization and embryogenesis to create new plants under the microscope. We are also keen to explore cell fate-determining mechanisms that drive plasticity in the plant's developmental processes.
At present, we are working on the following research themes:
- Microscopic recreation of fertilization and embryogenesis
- Creation of new plant hybrids
- Cell fate-determining patterns influencing plant developmental plasticity
- Genome editing using fertilized eggs
If you are interested in joining the graduate program and doing research with us, please contact us through email.
Current Projects
(1) Microscopic recreation of fertilization and embryogenesis
In sexually reproducing organisms, the egg (female gametophyte) and sperm (male gametophyte) fuse to produce a fertilized egg that develops into the next generation of individuals. In angiosperms, seeds consisting of an embryo and endosperm forms after multiple fertilization. During the initial stages, a series of important events in early embryogenesis occur within the fertilized egg - cell activation, mating and mixing of male and female genomes, activation of the developmental programming, reorganization of intracellular polarity, and daughter cell fate determination. The complex developmental process then proceeds from there. Since fertilized egg development occurs deep within the pistil, it has been challenging to analyze, with many of the underlying developmental mechanisms remaining unknown. Because of this, we have established an experimental system (in vitro fertilization) where we are able to generate fertilized eggs from electrically fused egg and sperm cells isolated from rice and wheat. Although we have started to understand some aspects of these developmental mechanisms, many other areas remain unclear and thus we continue to dig deeper.
(2) Creation of new plant hybrids
Wheat, rice, and maize, the three major grains, account for about 90% of the world's grain production. However, because they each belong to different subfamilies, interbreeding through hybridization continue to be a challenge, and their superior genetic resources have not been fully utilized. With human food production facing an unprecedented crisis due to the recent changes in climate and overpopulation, the need to establish a technology to overcome hybridization failure in these major grains have become imperative.
In our laboratory, we have developed a new means to produce wheat-rice hybrids by fusing gametes (egg and sperm cells) isolated from wheat and rice flowers. We have experimented on various combinations to produce many versions of wheat/rice cross-fertilized eggs analyzed their developmental process. By doing this, we have succeeded in artificially producing wheat-rice heteroploid fertilized eggs that grow into wheat-rice hybrids. This finding moves us closer toward the mutual utilization of wheat and rice genetic resources has potential to fully develop into a new breeding technology. Additionally since this IVF method can be adapted to many plant species with gametes, the application is not limited to just wheat and rice. Rather, it opens the door to creating distantly-related hybrids between many useful plants, such as maize, barley, and sugarcane. Furthermore, our understanding of the developmental process in the wheat-rice hybrids will also provide us insight into the development of distantly-related hybrids.
(3) Cell fate-determining patterns influencing plant developmental plasticity
In multi-cellular organisms, cells with many different functions come together to form a single individual. But how are these individual cell fates decided?
In both plants and animals, a fertilized egg can differentiate into and cell type. This totipotency gradually disappears later in the development, and individual cells differentiate into cells with characteristic functions. Once embryogenesis finishes, differentiation also concludes, and cells must be artificially transfected with genes (e.g. in iPS cells) in order to regain pluripotency. In plants, however, some cells in the apical meristem remain pluripotent stem cells. These are the cells that continuously generate new organs such as leaves, stems, and flowers even after embryogenesis is completed. Some fully-differentiated somatic cells also possess the ability to regenerate individuals through isolation and culture, suggesting that differentiated plant cells may be able to acquire differentiated pluripotency relatively easily. To understand this characteristic plasticity, we are currently working with rice, a monocotyledonous plant, and Arabidopsis thaliana, a dicotyledonous plant as model systems.
(4) Genome editing using fertilized eggs
Since the 2013 announcement of CRISPR/Cas9 as a new genome editing tool, research on genome editing have been progressing dramatically in the fields of fundamental plant research and breeding. However, in order to achieve widespread practical use, two problems must be solved: (1) the establishment of efficient redifferentiation system using tissue culture, and (2) the avoidance of genetic modification. To this end, we established a system to produce plants with edited genomes using direct introduction of the Cas9 protein-gRNA RNPs into fertilized rice egg cells that develop into genome-edited plants that are not transgenic.
The resulting plants have edited genomes but are not equivalent to transgenic plants. In particular, fertilized eggs from rice, wheat, and maize can be prepared using both in vitro fertilization systems and isolation from pollinated ovaries. Genome editing with these fertilized eggs could potentially develop into a new molecular breeding technology.
Staff Highlight
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Dr. Takashi Okamoto (岡本 龍史) Professor | Dr. Toshiko Furukawa (古川 聡子) Assistant Professor | Dr. Atsuko Kinoshita (木下 温子) Assistant Professor |
Email: | ||
okamoto-takashi[at]tmu.ac.jp | furukawa-toshiko[at]tmu.ac.jp | akinoshita[at]tmu.ac.jp |
| Read more: | ||
Lab Information: | ||
Recent Publications
Tety Maryenti, Shizuka Koshimizu, Nonoka Onda, Takayoshi Ishii, Kentaro Yano, Takashi Okamoto. Plant and Cell Physiology,
Aug 2024
Hajime Yamada, Norio Kato, Masako Ichikawa, Keiko Mannen, Takatoshi Kiba, Yuriko Osakabe, Hitoshi Sakakibara,
Minami Matsui, Takashi Okamoto. Plant & Cell Physiology, 65(5) 729-736, May 2024
Yilin Zhang, Daisuke Maruyama, Erika Toda, Atsuko Kinoshita, Takashi Okamoto, Nobutaka Mitsuda, Hironori Takasaki,
Masaru Ohme Takagi. FEBS Letters, Jan 2023
4. Genome editing approaches using reproductive cells/tissues in flowering plants
Erika Toda, Norio Kato, Tetsuya Higashiyama, Takashi Okamoto. Frontiers in Genome Editing, 4, Jan 2023
5. Isolation of gametes and zygotes from Setaria viridis
Erika Toda, Takatoshi Kiba, Norio Kato, Takashi Okamoto. Journal of Plant Research, 135(4) 627-633, Jul 2022
See more: (ResearchMap) (Google Scholar)
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