The 10th Asian Crop Science Association Conference

講演情報

Oral sessions

Crop Genetics and Physiology » O41: Genetic Improvement of Crop Yield

[O41] Genetic Improvement of Crop Yield

2021年9月9日(木) 09:45 〜 11:45 Room 4 (Oral) (Crop Genetics and Physiology)

Chair: Taichiro Ookawa (Tokyo University of Agriculture and Technology, Japan )
Chair: Hiroshi Fukayama (Kobe University, Japan)
Chair: Masahiro Kishii (International Maize and Wheat Improvement Center, Mexico)
Chair: Shunsuke Adachi (Tokyo University of Agriculture and Technology, Japan )

10:05 〜 10:25

[O41-02] A Challenge for the Improvement of Photosynthetic Capacity by the Introduction of C4-Like Rubisco in Rice

Hiroshi Fukayama1, Keita Shiomi1, Yuri Taketani1, Hiroki Yoshikawa2, Daisuke Sasayama1, Tomoko Hatanaka1, Tetsushi Azuma1, Takuya Yoshizawa2, Shun-ichi Tanaka2, Hiroyoshi Matsumura2 (1.Graduate School of Agricultural Science, Kobe University, Japan, 2.Department of Biotechnology, Ritsumeikan University, Japan)

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the key enzyme of photosynthetic CO2 fixation. Rubisco in C4 plants generally shows higher catalytic rate (kcat) than that in C3 plants. In our previous study, the chimeric incorporation of sorghum Rubisco small subunit (RbcS) significantly increased the Rubisco kcat in rice. In this study, we knocked out rice RbcS multigene family by CRISPR/Cas9 and completely replaced the rice RbcS with sorghum RbcS in rice Rubisco. Obtained hybrid-Rubisco (CSS-Rubisco) showed almost C4-plant-like catalytic properties, i.e., higher kcat and Km for CO2. Transgenic lines expressing the hybrid-Rubisco accumulated moderately reduced levels of Rubisco and showed slight but significantly higher photosynthetic capacity at high CO2 condition than non-transgenic rice. Grown under ambient CO2 condition (40 Pa), the total dry weight in CSS lines was significantly lower than that in WT, whereas it was recovered to the level of WT under elevated CO2 condition (100 and 300 Pa). The crystal structure of CSS-Rubisco in the sulfate-bound forms revealed a substantial structural difference in the β-hairpin (βC-βD) of RbcS around Leu101 in sorghum RbcS, which is likely to impact the flexibility of the 60s loop of Rubisco catalytic site. These results suggest that Leu101 in sorghum RbcS can be an important determinant of the kinetic properties of Rubisco and a promising target of improving the photosynthetic capacity in C3 plants.