Differential metabolites and key pathways in quinoa rhizosphere responding to salt stress: implications for salt...

As an important salt-alkali-tolerant crop, quinoa can respond to salt stress through various pathways. However, the response mechanisms of the rhizosphere microenvironment to salt stress require further exploration. This study aimed to investigate the effects of salt stress on the metabolic profile of quinoa rhizosphere soil and to explore its salt tolerance mechanisms at the metabolic level.

Using Ultra-high performance liquid chromatography coupled with quadrupole-Orbitrap mass spectrometry (UHPLC-Q-Orbitrap-MS)based untargeted metabolomics, combined with multivariate statistical analysis and KEGG pathway enrichment analysis, this study systematically compared the metabolic differences in rhizosphere soil between the salt-stressed group and the control group. The results showed that a total of 856 metabolites were identified, with 439 significantly differential metabolites screened out, including 344 up-regulated and 95 down-regulated metabolites. The differential metabolites primarily included lipids and lipid-like molecules, organic acids and their derivatives, organooxygen compounds, organic nitrogen compounds, and heterocyclic compounds. The accumulation of key differential metabolites indicated that quinoa responds to salt stress through multiple synergistic strategies, such as osmotic regulation, antioxidant defense, membrane lipid remodeling, as well as hormone signaling and acetic acid metabolism. KEGG enrichment analysis further revealed that pathways including phenylalanine metabolism, amino acid biosynthesis, and ATP-Binding Cassette transporters (ABC transporters) were significantly enriched, forming a systemic adaptation network encompassing defense substance synthesis, osmotic protection deployment, and substance transport regulation.

In conclusion, composite saline-alkali stress induces extensive reprogramming of metabolite composition in quinoa rhizosphere soil. The observed shifts in rhizosphere metabolites are closely linked to the salt tolerance adaptation of quinoa. This study offers a theoretical foundation for understanding rhizosphere metabolic responses and may inform strategies for improving crop performance in saline-alkali lands.