Identification of the Galactinol Synthase (GolS) Family in Medicago truncatula and Expression Analysis Under Abiotic Stress and Phytohormone Treatment

Galactinol synthase (GolS) serves as a pivotal enzyme in the biosynthesis of raffinose family oligosaccharides (RFOs) and assumes a crucial role in mediating plant responses to environmental stresses. However, a comprehensive exploration of the GolS gene family in the M. truncatula remains lacking. In this study, we identified five GolS genes (MtGolS) from the M. truncatula genome, and an analysis of evolution, domain, tissue expression, as well as their responses to various abiotic stresses and plant hormones was performed on these five genes. Comparative analysis revealed that the gene structure and domains of MtGolSs corresponded with those observed in GolS proteins in rice and Arabidopsis. Notably, the theoretical isoelectric point (pI) of MtGolS3 (8.31) was significantly surpassed that of its counterparts. And a segmental duplication event was found between MtGolS1 and MtGolS5. Furthermore, the expression patterns exhibited distinctive patterns for MtGolS3, characterized by predominant expression in flowers and shoot apical meristems, whereas MtGolS1, 2, 4, and 5 displayed heightened expression levels in seeds. Examination of promoters and expression profiles disclosed the responsiveness of the MtGolS genes to diverse abiotic stresses and phytohormone treatments. Specifically, MtGolS1, 2, 4, and 5 were significantly induced under drought, cold, and salt stress conditions. Additionally, MtGolS1, 3, 4, and 5 were upregulated by auxin (IAA) and gibberellin (GA), but inhibited by abscisic acid (ABA). Additionally, miRNA prediction analysis identified a total of 23 miRNA target sites within the five MtGolS genes, targeted by 17 distinct miRNAs. These findings furnish fundamental insights for further delving into the functional mechanisms of GolS genes in M. truncatula.