Molecular cloning and stress-dependent regulation of a glutamine synthetase gene in Chinese cabbage

A new glutamine synthetase (GS, EC 6.3.1.2) gene C-GS1 (GenBank accession no.AY773089) was isolated from Chinese cabbage (Brassica rapa ssp. pekinensis). Sequence and structural analysis showed that C-GS1 protein contained structural domains conserved within plant GS1s. The amino acid sequence of C-GS1 had extensive homology with those of GS1s from other higher plants. The phylogenetic tree displayed that the C-GS1 was the closest to GS1 from Brassica napus. C-GS1 was preferentially expressed in roots and stems rather than in leaves. Cold treatment (4°C) and water logging stress enhanced and abscisic acid, H2O2, and salicylic acid repressed the levels of C-GS1 transcripts. This study indicates that stress factors regulate the C-GS1 expression at the transcriptional level.