The impact of GmTSA and GmALS on soybean salt tolerance: uncovering the molecular landscape of amino acid and secondary metabolism pathways.

GmTSA and GmALS were screened out for salt stress in soybean and explore the poteintial amino acid secondary metabolism pathways. Soybean (Glycine max L.) is an oil and protein crop of global importance, and salinity has significant effects on soybean growth. Here, a population of soybean chromosome segment substitution lines was screened to identify highly salt-tolerant lines. In total, 24 quantitative trait loci (QTLs) on seven chromosomes were associated with salt tolerance, and CSSL_R71 was selected for further analysis. Although numerous genes were differentially expressed in CSSL_R71 in response to salt statically no differently, transcript levels of classical salt-response genes, including those of the salt overly sensitive pathway. Rather, salt tolerance in CSSL_R71 was associated with changes in amino acid and lipid metabolism. In particular, changes in p-coumaric acid, shikimic acid, and pyrrole-2-carboxylic acid levels accompanied salt tolerance in CSSL_R71. Eleven differentially expressed genes (DEGs) related to amino acid and secondary metabolism were identified as candidate genes on the substituted chromosome fragment. Six of these showed differences in coding sequence between the parental genotypes. Crucially, overexpression of GmTSA (Glyma.03G158400, tryptophan synthase) significantly enhanced salt tolerance in soybean hairy roots, whereas overexpression of GmALS (Glyma.13G241000, acetolactate synthase) decreased salt tolerance. Two KASP markers were developed for GmALS and used to genotype salt-tolerant and salt-sensitive lines in the CSSL population. Non-synonymous mutations were directly associated with salt tolerance. Taken together, these data provide evidence that changes in amino acid and secondary metabolism have the potential to confer salt tolerance in soybean.