Resilience in primary metabolism contributes to salt stress adaptation in Sesuvium portulacastrum (L.)

Sesuvium portulacastrum (L.) is a facultative halophyte that grows in subtropical coastal sides of the eastern and western regions of India. In the present study, the activation of antioxidant machinery was observed at 8 and 24 h after 250 mM NaCl stress treatment. Further, GC-MS/MS based metabolomics was performed, independently in root (NR8 and NR24) and shoot (NS8 and NS24). A total of 53 and 62 metabolites were detected in roots and shoots, respectively, that mainly included sugars, amino acids, organic acids and polyols. On the basis of statistical significance, sucrose and ethanolamine were identified as differentially altered metabolites (DAMs) shared under all the treatment conditions. Heat-map based clustering analysis substantiated the role of sugars and amino acids in NR8; while, sugars in NS8/NS24 treatments. For most of the DAMs, extent of change at NR24 was significantly dampened than NR8, which also coincided with reduced correlation strength between different metabolite groups, indicating partial metabolite restoration. The enrichment analysis identified sugars, amino acid and TCA cycle metabolism as major pathways altered under salt stress conditions. A total of 30 metabolomic datasets from 7 different halophytes, including the present study, were utilized to perform meta-analysis. On the basis of cumulative pathway score (CPS) of both root and shoot, aspartate-alanine-glutamate (290.62) was identified as the most significant pathway followed by arginine biosynthesis (0.62) and glyoxylate-dicarboxylate metabolism (0.46) that significantly contributed to salt-adaptation in halophytes. Thus, the holistic analysis of salt-responsive metabolites/pathways from halophytes will pave the way for enhancing salt-tolerance in crop plants.