Comparative analysis of metabolite changes in two contrasting rice genotypes in response to low-nitrogen stress

Identification of metabolites responsible for tolerance to low nitrogen availability (low-N) will aid in the genetic improvement of rice yield under nitrogen deficiency. In this study, a backcross introgression line (G9) and its recurrent parent Shuhui 527 (SH527), which show differential responses to low-N stress, were used to identify metabolites associated with low-N tolerance in rice. Differences in metabolite contents in the leaves of G9 and SH527 at three growth stages under low-N stress were assessed by gas chromatography-mass spectrometry. Many metabolites, including amino acids and derivatives, were highly enriched in G9 compared with SH527 under the control condition, suggesting that the two genotypes had basal metabolite differences. Low-N stress induced genotype-specific as well as growth stage-dependent metabolite changes. Metabolites induced specifically in G9 that were involved in glycolysis and tricarboxylic acid metabolism were enriched at the tillering and grain filling stages, and metabolites involved in nitrogen and proline metabolism were enriched at the booting stage. Enrichment of pyroglutamate, glutamate, 2-oxoglutarate, sorbose, glycerate-2-P, and phosphoenolpyruvic acid in G9 suggests that these metabolites could be involved in low-N stress tolerance. The results presented here provide valuable information for further elucidation of the molecular mechanisms of low-N tolerance in crops.