Stress-inducible expression of GmDREB1 conferred salt tolerance in transgenic alfalfa

In attempt to improve salt tolerance of alfalfa (Medicago sativa L.) plants, a soybean DREB orthologue, GmDREB1, was introduced into alfalfa plants under the control of Arabidopsis Rd29A promoter. Its incorporation and expression in transgenic plants were confirmed by DNA and RNA gel-blot analyses. The level of salt tolerance of transgenic lines was significantly higher than that of wild-type control plants as measured by ion leakage, chlorophyll fluorescence value, contents of free proline and total soluble sugars. Moreover, northern blot analysis revealed that the transcript level of Delta 1-pyrroline-5-carboxylate synthase (P5CS) was up-regulated in the transgenic plants. These results suggested that the stress-inducible expression of GmDREB1 conferred salt tolerance in transgenic alfalfa plants. In addition, no visible phenotypic alternations were observed in the transgenic plants due to the use of stress-inducible Rd29A promoter. It was the first to describe transgenic expression of DREB genes in alfalfa and these transgenic lines with high salt-tolerance are of significance in the forage breeding.