A research team from University of Tsukuba, Tohoku University, RIKEN Center for Environmental Science and Resources, Gifu University, Chiba University and the Japan International Research Center for Agricultural Sciences (JIRCAS) revealed that OsGS1;1, an isozyme of cytosolic glutamine synthase (OsGS1) essential for nitrogen assimilation in rice, is significantly involved in chloroplast formation in the non-photosynthetic roots. Nitrogen is one of the three essential nutrients of fertilizers and is a component of chlorophyll and amino acids which are essential for plant survival. Nitrogen taken into plants is converted to ammonium, and assimilated by glutamine synthase (GS) into the amino acid glutamine. Plants have multiple genes encoding cytosolic GS1, but it is unclear why plants have multiple forms of GS1 and the functions of these isozymes.

This study focused on OsGS1;1 and OsGS1;2 isozymes which are expressed in the early growth stage of rice. Analysis of mutant rice in which each gene was disrupted revealed that the roots of Osgs1;1 mutants lost the balance for accumulation of sugars and amino acids whereas Osgs1;2 mutants showed only a decrease in the amount of amino acids. In addition, the Osgs1;1 mutant forms chloroplasts in the non-photosynthetic roots. OsGS1;1 is involved in a wide range of phenomena such as maintaining metabolic homeostasis and chloroplast formation in rice roots, whereas Osgs1;2 is particularly involved in the regulation of amino acid biosynthesis during metabolism.

The results of this research were published online in the journal Plant Physiology on February 6, 2020.

Authors

Miyako Kusano, Atsushi Fukushima, Mayumi Tabuchi-Kobayashi, Kazuhiro Funayama, Soichi Kojima, Kyonoshin Maruyama, Yoshiharu Y Yamamoto, Tomoko Nishizawa, Makoto Kobayashi, Mayumi Wakazaki, Mayuko Sato, Kiminori Toyooka, Kumiko Osanai-Kondo, Yoshinori Utsumi, Motoaki Seki, Chihaya Fukai, Kazuki Saito, and Tomoyuki Yamaya

Title

Cytosolic GLUTAMINE SYNTHETASE 1;1 modulates metabolism and chloroplast development in roots

Journal

Plant Physiology DOI: https://doi.org/10.1104/pp.19.01118

Dr. KUSANO Miyako

Graduate School of Life and Environmental Sciences
University of Tsukuba
Tsukuba 305-8507, Japan
E-mail: kusano.miyako.fp@u.tsukuba.ac.jp