Abstract
High soil salinity is one of the most damaging abiotic stresses affecting crop productivity by generating osmotic stress and ion toxicity. In this study, we investigated the metabolic responses of two transgenic rice (Agb0103) lines overexpressing CaMsrB2, L-8 (single-copy insertion) and L-23 (double-copy insertion) in comparison with the non-transgenic parental Ilmi cultivar under conditions involving salt-mediated stress (0, 75, 150, and 225 mM NaCl). Metabolite profiling was conducted using gas chromatography - time-of-flight mass spectrometry, targeting 63 hydrophilic and lipophilic compounds. Comparative analysis after treatment with 0 and 225 mM NaCl for 7 days revealed that the metabolites that showed significant differences included sugars, 10 amino acids, and 6 organic acids. The transgenic lines exhibited fewer changes in proline and γ-aminobutyric acid levels, which are known indicators of salt-induced leaf damage. Additionally, methionine content, which is likely influenced by CaMsrB2 expression, was altered under salt stress. Transgenic lines also accumulated higher levels of sugars, which contribute to reactive oxygen species scavenging, than Ilmi. Conversely, amino acids, such as asparagine, aspartic acid, glutamine, and glutamic acid, showed contrasting trends in the transgenic lines and Ilmi. These differences may be attributed to the roles of glutamic acid and glutamine in nitrogen metabolism and the involvement of glutamine synthetase in osmotic stress tolerance. Overall, this study provides foundational data for understanding the metabolic mechanisms underlying abiotic stress resistance in CaMsrB2-expressing rice and highlights the potential role of this gene in enhancing salt stress tolerance through metabolic regulation.