Integrative physiological and metabolomics study reveals adaptive strategies of wheat seedlings to salt and heat stress combination

Acclimation of wheat (Triticum aestivum L.) genotypes to arid and semi-arid cultivation areas is important for its domestication as food crops in those regions. In this study, physiological and metabolic responses of the seedlings of two distinct wheat genotypes to salt and heat stress combination is investigated to unravel their possible adaptive strategies. The seedlings were divided into control and combination of salt (150 mM NaCl) and heat stress (42 °C for 4 h) treatment groups. The seedlings were then characterized at 5 days post stress exposure. The growth characterization revealed predominant stress effects on the shoot development. Fahng 60, a warm-adapted cultivar, showed better growth compared to Samerng 2 under stress condition. Interestingly, decreased relative water content and chlorophyll a content was observed in Fahng 60 under the combined stress, suggesting detrimental effects on water status and photosynthetic capacity. Oxidative stress responses were evidenced with malondialdehyde accumulation in both cultivars; however, only Fahng 60 accumulated proline in its response. Leaf primary metabolite profiles revealed amino acids, sugars, and sugar derivatives as the major discriminant metabolites under the stress. In both genotypes, the ABC transporters, glucosinolate metabolism, aminoacyl-tRNA biosynthesis, cyanoamino acid metabolism, and galactose metabolism were the key overrepresented pathways under the stress combination. This study demonstrates that despite differences in physiological alterations between the two wheat cultivars, metabolically they may utilize similar biochemical processes to confer adaptive strategies under the combined salt and heat stress.