Combining multi−omics analysis of gibberellin promoting nitrogen uptake and PbNRT2.1 research provides new insights into sustainable Pyrus betulaefolia rootstock production

‘Duli’ ( Pyrus betulaefolia ) is widely used as a rootstock in commercial pear orchards. Nitrogen (N) is vital elements in the modulating the growth and development of ‘Duli’. But the molecular mechanism by which GA regulates the N pathway is largely unknown. In this study, physiology, metabolomics, and transcriptomics were utilized to investigate the potential effects of GA 3 on ‘Duli’ seedlings growth and metabolism under low and normal nitrate (NO 3 − ) concentrations. Results showed that, under both treatments, exogenous GA 3 improved the growth, photosynthetic characteristics ( Pn , Gs , Tr , and qP ), GA 3 content, N content, and N − pathway enzyme activity of ‘Duli’. Furthermore, RNA−Seq revealed that GA synthesis, N uptake, and metabolism pathways were enriched by the application of GA 3 . Metabolome analysis uncovered differential metabolites mainly concentrated in secondary metabolite and flavonoid synthesis pathways. Moreover, according to the combined transcriptomics and metabolomics analysis, the biosynthesis of both flavonoids and zeatin riboside is enriched. The related gene of PbNRT2.1 expression level is induced by exogenous GA₃, and PbNRT2.1 located to the cell membrane. In addition, the growth and N content of ‘Duli’ callus and tobacco plants significantly improved under PbNRT2.1 −OE lines. This study provides a reference for reducing the pear N fertilizer application and achieving pear sustainable development. • Exogenous GA 3 augments N uptake and growth of ‘Duli’ seedlings under normal or low NO 3 − stress. • Transcriptomics analysis shows that applying GA 3 enriches GA synthesis, N uptake, and metabolism pathways. • Integrated metabolomics and transcriptomics analyses reveal enriched flavonoid and zeatin riboside synthesis. • PbNRT2.1 localizes at the cell membrane, where overexpression promotes N uptake that responds to GA 3 .