Integrated Metabolomics and Transcriptomics Analyses Reveal Resistance to Salt Stress in Wild Soybean (Glycine soja) During the Post-Germination Growth Period

Due to increasingly serious soil salinisation, exploring high-quality closely related wild species is an effective means to solve food security problems. In this study, based on comprehensive metabolomics and transcriptomics analyses of the types, quantities, metabolic pathways and gene expression of small molecule metabolites in cotyledons and embryo axis/root, we report the strategies used by barren-tolerant wild soybean (GS2) to resist salt stress during the post-germination period. Our results showed that salt tolerance in GS2 cotyledons mainly involves the enhanced mobilisation of reserves, including lipid and sugar breakdown and utilisation, as well as protein breakdown and, in particular, the transport of amino acids to the embryo axis/root. Moreover, antioxidant capacity is enhanced through the promotion of ascorbic acid and naringin synthesis. We also found that under salt stress, the GS2 embryo axis/root accumulates proline by promoting the ornithine biosynthetic pathway, while stimulating glutathione metabolism to eliminate excess reactive oxygen species and restore oxidative balance. In addition, to establish and elongate the embryo axis/root, lignin synthesis is enhanced by the promotion of the shikimic acid pathway, which compensates for the decrease in cell wall support caused by salt stress. This study lays the foundation for developing and utilising high-quality wild plant resources.