A New Perspective on the Role of Glutamine Synthetase in Nitrogen Remobilization in Wheat ( L.).

Glutamine synthetase (GS), a key enzyme in plant nitrogen metabolism, is closely related to nitrogen remobilization. However, how GS isoforms participate in nitrogen remobilization remains unclear. Here, the spatiotemporal expression of the gene family after anthesis was investigated, and the results showed that TaGS1;1 was mainly encoded by , while the other isozymes were mainly encoded by localized on the A and D subgenomes. had the highest expression level, especially in rachis and peduncle. Furthermore, immunofluorescence showed TaGS1;2 was located in the phloem of rachis and peduncle. GUS (β-glucuronidase) staining confirmed that activity was mainly present in the vascular system of leaves, roots, and petal of . Ureides, an important transport form of nitrogen, were mainly synthesized in flag leaves and transported to grains through the phloem of peduncle and rachis during grain filling. , which encodes the enzyme that degrades ureides to release NH, had a higher expression in rachis and peduncle and was synchronized with the increase in NH concentration in phloem, indicating that NH in phloem is from ureide degradation. Taking the above into account, TaGS1;2, which is highly expressed in the phloem of peduncle and rachis, may participate in N remobilization by assimilating NH released from ureide degradation.