Analysis of the expression of nine salt response genes in Medicago sativa

Alfalfa is the most-cultivated and most widely used forage legume in the world. Its moderate salt tolerance limits its cultivation and production in Northern China because of the soil salinization in this area. Therefore, improving alfalfa salt tolerance is important for both scientific research and commercial production. In this study, we used Medicago sativa ‘Longmu 801’ as a model to analyze the expression patterns of 9 salt response genes selected for salt stress proteomics using quantitative real-time PCR under various NaCl concentrations. The results showed that time and NaCl concentration had significant effects on the relative expression of all 9 genes, indicating that these 9 genes play roles in alfalfa’s salt stress response. The relative expression levels of G6PI, ABP19a, Trx-h1, PR bet 1, FBPA, 6PGDH, and ALDH genes were all significantly up-regulated in alfalfa treated with the tested NaCl stress concentrations for 1 h. RRM and GDPD were obviously up-regulated after 2 h of NaCl treatment. Except G6PI, the relative expression of the remaining 8 genes under 0.4% NaCl stress was much higher than that under 0.2% and 0.8% NaCl stress. These genes are mostly involved in carbohydrate metabolism, signal transduction, and stress response. This result demonstrated that alfalfa’s salt tolerance is complicated and is a result of multi-gene expression and the interactions of many metabolic pathways. This result is useful for further research on alfalfa salt response genes and selective breeding of alfalfa using molecular markers.