Genome-wide identification of the trehalose-6-phosphate synthase gene family in alfalfa (Medicago sativa L.) reveals involvement of MsTPS16 in tolerance to saline-alkali stress

Trehalose-6-phosphate synthase (TPS) is an indispensable enzyme in the trehalose synthesis pathway, which plays an active role in plant responses to abiotic stress. However, the identification of the TPS gene family in alfalfa and its effects under saline-alkali stress remain unclear. This study identified 38 MsTPS genes that could be categorized into two classes. Class I genes had more introns than did Class II genes. Class II genes possessed the full motif, whereas Class I genes lacked motif 8. The evolutionary pattern of MsTPS genes primarily manifested as fragment duplication events. The promoter regions of the MsTPS genes were enriched with multiple hormone-and stress-response cis-acting regulatory elements. Transcriptome analyses revealed that nine MsTPS genes were upregulated under saline-alkali stress. A qRT-PCR analysis revealed that MsTPS16 exhibited the most significant upregulated expression. Subcellular localization analyses revealed that the MsTPS16 protein was mainly localized in the cytoplasm, vacuolar membrane, and cell membrane. The heterologous expression of MsTPS16 promoted yeast growth under saline-alkali stress, and its overexpression in alfalfa hairy roots reduced the reactive oxygen species content and enhanced the expression of genes encoding the key enzymes of the antioxidant pathway under saline-alkali stress. This study provides comprehensive insights into the functional characterization of the MsTPS gene family and highlights a potentially influential gene involved in tolerance to saline--alkali stress in alfalfa.