Abstract
Rice (Oryza sativa L.) plants possess three homologous but distinct genes for cytosolic glutamine synthetase (GS1): there are OsGS1;1, OsGS1;2 and OsGS1;3. We characterized knockout mutants caused by insertion of endogenous retrotransposon Tos17 into OsGS1;1. Homozygously inserted mutants showed severe retadation in growth rate and grain filling.
The mutants expressed no OsGS1;1 mRNA in the roots, leaf blade, and leaf sheath, but expressed OsGS1;2 mRNA at the normal level as in the wild-type, when real time RT-PCR was carried out. The glutamine pool in the leaf blades of the mutants was approximately 60% 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. The results indicate that GS1;1 is important for normal growth in rice and other two GS1s as well as GS2 were not able to compensate for GS1;1 function.
