Flooded soybean metabolomic analysis reveals important primary and secondary metabolites involved in the hypoxia stress response and tolerance

Flooded soils have reduced oxygen available for efficient ATP production through oxidative phosphorylation in plants. The effect of flooding stress on most commercial food crops, including soybeans, has not been widely studied. Here, metabolic identification was performed using 1H NMR spectroscopy aiming at determining the differences between two soybean cultivars (namely, BR4 and Embrapa 45, which are sensitive and moderately tolerant, respectively, to flooding stress) by comparing the responses to flooding stress in roots and leaves. Soybean plants were cultivated in a growth chamber under ideal conditions until the V3 stage, when flooding stress was induced for 2, 7, and 12 days. Physiological parameters and the plant biomass accumulation were determined, and root and leaf samples were collected for metabolomic assays using 1H NMR spectroscopy. The metabolomic data were supported by a gene expression analysis. Our results indicate that flooding stress strongly affects both the primary and secondary metabolism in soybean plants. Most of the altered compounds are involved in carbon and nitrogen metabolism as well as the phenylpropanoid pathway. Different responses were observed between the roots and leaves, as well as between flood-tolerant and flood-sensitive cultivars.