Department of Bioengineering Sciences

Division of Molecular Cell Function


  FAX: +81-52-789-5228
Prof. KITAJIMA, Ken D. Sci. kitajima@
Assoc. Prof. SATO, Chihiro D. Sci. chi@

Glycan chains are covalently attached to proteins and lipids to form glycoproteins and glycolipids, i.e., “glycoconjugates”, and cover the entire surface of cells in any bioorganisms on our planet. They play important roles in a myriad of biological processes, such as cell adhesion, tissue and organ formation, and host recognition to pathogens or symbionts. In most cases, they play roles in various cell societies. However, there are still many glycan chains that remain to be elucidated for their biological functions. Thus, our research goal is to understand how glycan chains function on the cell surface as well as soluble glycoconjugates. Two projects are going on in our laboratory:
(1) Glyco-atmosphere, a field of glycans on the surface of cells and glycoconjugates: Demonstration of its existence and biological significance;
(2) Diversity and heterogeneity of sialic acids and polysialic acids: Their structure, biosynthesis, function, and applications.
Glycobiology, our research field, is relatively young and challenging, but has become more and more important as a leading area of biological sciences, especially in the current post-genomic era.
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  Fax: +81-52-789-5214
Prof. ASHIKARI, Motoyuki D. Agr. ashi@
Asst. Prof. NAGAI, Keisuke D. Agr. nagai.k@

Research theme

Habitat expansion is an important adaptational strategy of living organisms to survive unfavorable environments. However, overcoming adverse environmental conditions is not easy for plants due their sedentary nature. To overcome this constraint, plants evolve and gain new functions to fit in severely inhospitable environments and survive adverse conditions.

In understanding the different adaptational responses of plants to adverse environments, the production and analysis of loss-of-function mutants have been an essential tool. In the case of rice, for example, many mutants have been identified. However, insights into the possible multitude of traits present in many species of rice have been limited instead to the study of characters that are present in rice cultivars. In 10,000 years of crop domestication, cultivars have evolved through human selection of crops for important agronomic characters including non-shattering (i.e. of grains), high production and non-dormancy. Due to such focus of selection, many important characters including stress tolerance and disease resistance that are present in wild species have been lost. Particularly in rice, many wild species have important and unique characters that cultivars do not have. It is on this fact that I founded my belief that rice cultivars are mutants and the wild rice species are wild types.

The genus Oryza has 24 species (22 wild rice species + 2 cultivated species) distributed all over Asia, North Africa, South Africa and Australia. Each of the 22 wild rice species has its own adaptation to its native environment. Comparison of wild rice species and cultivars can provide us with insights into the unique characters present in wild rice but not in the cultivars. To date, several important characters that confer fitness to adverse conditions in wild rice have been identified. Some of these characters use plant hormone signaling for adaptation. Our laboratory aims at elucidating the mechanistic role of plant hormones in the environmental adaptation and survival of plants.

Representative papers

Ashikari, M., Sakakibara, H., Lin, S., Yamamoto, T., Takashi, T., Nishimura, A., Angeles, E. R., Qian, Q., Kitano, H. and Matsuoka, M. (2005) Cytokinin oxidase regulates rice grain production. Science 309, (5735) 741-745.

Ueguchi-Tanaka*, M., Ashikari*, M., Nakajima, M*., Itoh, H., Katoh, E., Kobayashi, M., Chow, T.-Y., Hsing, Y. C., Kitano, H., Yamaguchi, I. and Matsuoka, M. (2005) GIBBERELLIN INSENSITIVE DWARF1 encodes a soluble receptor for gibberellin. Nature 437, (7059) 693-698. *:Equal contribution

Sasaki, A., Itoh, H., Gomi, K., Ueguchi-Tanaka, M., Ishiyama, K., Kobayashi, M., Jeong, D.H., An, G., Kitano, H., Ashikari, M. and Matsuoka, M. (2003) Accumulation of phosphorylated repressor for gibberellin signaling in an F-box mutant. Science 299, (5614) 1896-1898.

Sasaki, A., Ashikari, M., Ueguchi-Tanaka, M., Itoh, H., Nishimura, A., Swapan, D., Ishiyama, K., Saito, T., Kobayashi, M., Khush, G. S., Kitano, H. and Matsuoka, M. (2002) A mutant gibberellin-synthesis gene in rice. Nature 416, (6882) 701-702.

Lab. Members
Professor: Motoyuki Ashikari
Postdoc: Kotaro Miura
Postdoc: Yoko Hattori
Postdoc: Xianjun Song
Ph.D student (D3): Kenji Asano
Ph.D student (D2): Eiji Yamamoto
Ph.D student (D1): Rosalyn Shim
MS student (M2): Keisuke Nagai
MS student (M1): Chihiro Sato
Undergraduate student: Shizuka Furukawa
Undergraduate student: Atsushi Matsubara
Technical staff: Midori Ito
Technical staff: Kiyomi Sakata


Fax: +81-52-789-5214
Prof. HATTORI, Tsukaho D. Agr. hattori@
Assoc. Prof. UEGUCHI, Chiharu D. Sci. cueguchi@
Assoc. Prof. TAKEDA, Shin D. Agr takeda@