Severe reduction in growth rate and grain filling of rice mutants lacking OsGS1;1, a cytosolic glutamine synthetase1;1

Authors

  • Mayumi Tabuchi,

    1. Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai 981-8555, Japan,
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  • Kenjiro Sugiyama,

    1. Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai 981-8555, Japan,
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  • Keiki Ishiyama,

    1. Metabolic Function Research Group, Plant Science Center, RIKEN, 1-7-22 Suehiro, Tsurumi-ku, Yokohama 230-0045, Japan, and
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  • Eri Inoue,

    1. Metabolic Function Research Group, Plant Science Center, RIKEN, 1-7-22 Suehiro, Tsurumi-ku, Yokohama 230-0045, Japan, and
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  • Tadashi Sato,

    1. Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan
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  • Hideki Takahashi,

    1. Metabolic Function Research Group, Plant Science Center, RIKEN, 1-7-22 Suehiro, Tsurumi-ku, Yokohama 230-0045, Japan, and
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  • Tomoyuki Yamaya

    Corresponding author
    1. Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai 981-8555, Japan,
    2. Metabolic Function Research Group, Plant Science Center, RIKEN, 1-7-22 Suehiro, Tsurumi-ku, Yokohama 230-0045, Japan, and
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(fax +81 22 717 8787; e-mail tyamaya@biochem.tohoku.ac.jp).

Summary

Rice (Oryza sativa L.) plants possess three homologous but distinct genes for cytosolic glutamine synthetase (GS1): these are OsGS1;1, OsGS1;2, and OsGS1;3. OsGS1;1 was expressed in all organs tested with higher expression in leaf blades, while OsGS1;2, and OsGS1;3 were expressed mainly in roots and spikelets, respectively. We characterized knockout mutants caused by insertion of endogenous retrotransposon Tos17 into the exon-8 (lines ND8037 and ND9801) or the exon-10 (line NC2327) of OsGS1;1. Mendelian segregation occurred in each progeny. Homozygously inserted mutants showed severe retardation in growth rate and grain filling when grown at normal nitrogen concentrations. Abnormal mRNA for GS1;1 was transcribed, and the GS1 protein and its activity in the leaf blades were barely detectable in these mutants. The glutamine pool in the roots and leaf blades of the mutants was lower than that of the wild type. Re-introduction of OsGS1;1 cDNA under the control of its own promoter into the mutants successfully complemented these phenotypes. Progeny where Tos17 was heterozygously inserted or deleted during segregation showed normal phenotypes. The results indicate that GS1;1 is important for normal growth and grain filling in rice; GS1;2 and GS1;3 were not able to compensate for GS1;1 function.

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