Abstract

Melilotus albusis a high-quality forage, due to its high protein content, and aboveground biomass and salt tolerance. Rab (Ras-related protein in the brain) proteins are the largest GTPase family which play a key role in intracellular membrane transport, and manyRabgenes have been identified in eukaryotes. The growth and distribution ofM. albusare severely hampered by soil salinization. However, little is known about candidate genes for salt tolerance inM. albus. In this study, 27Rabfamily genes were identified for the first time fromM. albus, and divided into eight groups (Groups A-H). The number of introns inMaRabsranged from one to seven, with most genes containing one intron. In addition, most MaRab proteins showed similarities in motif composition. Phylogenetic analysis and structural-domain comparison indicated thatRabfamily genes were highly conserved inM. albus. Members of the MaRab gene family were distributed across all eight chromosomes, with the largest distribution on chromosome 1. Prediction of the protein interaction network showed that 24 Rab proteins exhibited protein–protein interactions. Analysis of the promotercis-acting elements showed thatMaRab-gene family members are extensively involved in abiotic stress responses. RNA-seq data analysis of theMaRab-gene-expression patterns suggested that theRabgene family possesses differentially expressed members in five organs and under salt stress, drought stress, and ABA (Abscisic Acid) treatment. Differentially expressed genes under drought stress, salt stress and ABA stress were validated by quantitative real-time PCR. Furthermore, heterologous expression in yeast was used to characterize the functions ofMaRab1andMaRab17, which were upregulated in reaction to salt stress. In summary, this study provided valuable information for further research into the molecular mechanism of the response ofM. albusto saline stress, as well as the possibility of developing cultivars with high salt-resistance characteri