Metabolic Profile of Transgenic Birch Plants with the Conifer Cytosolic Glutamine Synthetase Gene GS1

ve: Increasing tree productivity by genetic engineering methods is one of the main trends of forest biotechnology. A promising strategy for this is to improve the use efficiency of nitrogen, which is the main limiting factor of plant growth. For this purpose, the GS1 gene from Scots pine was transferred to downy birch (Betula pubescens) plants. This gene encodes the cytosolic form of glutamine synthetase, the main enzyme of nitrogen metabolism in plants. Methods: To assess the effects of insertion of this gene, the birch plant metabolome was analyzed using GC-MS and HPLC-MS. Results and Discussion: GC-MS analysis found 197 metabolites in birch extracts, but the metabolomes of two transgenic clones showed no statistically significant differences from the control. Using the S-plot based on the OPLS-DA model, 32 metabolite markers affecting the separation of control and transgenic birch plants were detected; 22 of them were identified. Three metabolites among them were nitrogen-containing, including γ-aminobutyric acid, the immediate precursor of which is glutamine. HPLC-MS analysis found 48 metabolites, but transgenic plants did not differ from the control. GC-MS, however, showed a decrease in the content of two phenolic compounds in transgenic plants, which is characteristic of improved nitrogen supply. Conclusions: The study shows that modification of nitrogen metabolism in birch plants does not significantly affect the biochemical composition of tree shoots.