Integration of Physiological and Transcriptomic Approaches in Investigating Salt-Alkali Stress Resilience in Soybean

Salt-alkali stress is a key factor affecting plant development and production, altering essential physiological and metabolic processes within plants. Particularly, soybean (Glycine max) exhibits a wide range of saline-alkali tolerance in soybean germplasms. Hence, the objective of this research was to pinpoint potential genes that react to saline-alkali stress through a comparative transcriptome analysis of two distinct soybean varieties exposed to such stress conditions. The two soybean varieties, including salt-tolerant Heinong531 and salt-sensitive 20_1846, were used for RNA-seq analysis. Nine physiological parameters including malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH), peroxidase (POD), proline, catalase (CAT), soluble protein, scavenging rate of hydroxyl radical, and soluble sugar activity were measured under the saline-alkaline treatment series of 0,1,2,3,4 days. The results showed that the levels of MDA, proline, and catalase contents decreased significantly, while levels of GSH and POD contents significantly increased. A total of 200 saline-alkali tolerance responsive differentially expressed genes (DEGs) were identified, comprising 93 up-regulated genes and 107 down-regulated. The functional gene ontology analysis for these 200 DEGs, where 29 key DEGs were found to be involved in the regulation of 14 GO pathways responding to salt-alkaline stress which have been previously considered as vital for salt resistance mechanisms in soybean. Remarkably, the association analysis between physiological parameters and Differentially Expressed Genes (DEGs) under salt-alkali stress conditions demonstrated that distinct soybean cultivars exhibited unique patterns of gene expression, ultimately resulting in alterations in physiological indices as a response to salt stress. This study offers a compilation of potential genes worthy of additional exploration concerning their role in enhancing soybean's resistance to salt-alkali stress.