Isolation and Charactarization of Rice Mutants Inserted Retrotransposon Tos17 Into Cytosolic Glutamine Synthetase Gene

Abstract

Cytosolic glutamine synthethase (GS1) in rice (Oryza sativa L.) is probably important in the export of glutamine from senescing leaves. To prove this function of GS1, mutants lacking GS1 expression have been screened and characterized.
GS1 mutants (osgs1) were isolated from the Tos17-insertion lines of rice (distributed from the Rice Genome Project by Hirochika and Miyao). It is confirmed that Tos17 was inserted into the exon 8 of GS1 gene. This mutant contained undetectable amount of GS1 protein and its activity. GS1 protein is accumulated in companion cells in wild-type rice, but not in the mutant. Mutants were flowering but the seeds obtained were mostly sterile. Other four GS1-knock out lines were independently isolated by a PCR screening. The lines inserted Tos17 into either the exon 8 or exon 10 showed the same phenotype, i.e. growth retardation, dwarf, sterile, etc., as osgs1 mutant.