The overexpression of the algal glutamine synthetase (GS) gene DvGS1 in
Arabidopsis thaliana resulted in higher plant biomass and better growth
phenotype. The purpose of this study was to recognize the biological
mechanism for the growth improvement of DvGS1-transgenic Arabidopsis. A
series of molecular and biochemical investigations related to nitrogen and
carbon metabolism in the DvGS1-transgenic line was conducted. Analysis of
nitrogen use efficiency (NUE)-related gene transcription and enzymatic
activity revealed that the transcriptional level and enzymatic activity of
the genes encoding GS, glutamate synthase, glutamate dehydrogenase, alanine
aminotransferase and aspartate aminotransferase, were significantly
upregulated, especially from leaf tissues of the DvGS1-transgenic line under
two nitrate conditions. The DvGS1-transgenic line showed increased total
nitrogen content and decreased carbon: nitrogen ratio compared to wild-type
plants. Significant reduced concentrations of free nitrate, ammonium,
sucrose, glucose and starch, together with higher concentrations of total
amino acids, individual amino acids (glutamate, aspartate, asparagine,
methionine), soluble proteins and fructose in leaf tissues confirmed that the
DvGS1-transgenic line demonstrated a higher efficiency of nitrogen
assimilation, which subsequently affected carbon metabolism. These improved
metabolisms of nitrogen and carbon conferred the DvGS1-transgenic Arabidopsis
higher NUE, more biomass and better growth phenotype compared with the
wild-type plants.
The better growth phenotype of DvGS1-transgenic arabidopsis thaliana is attributed to the improved efficiency of nitrogen assimilation
