Salt stress tolerance analysis of rgMT gene transformed Medicago sativa

In this study, a metallothionein gene (rgMT) cloned from rice was transformed into Medicago sativa cv. “Nongjing No. 1” using the Agrobacterium-mediated method. Resistant seedlings were tested by PCR and northern blotting, and the results showed that rgMT gene was transformed into M. sativa genome, and was normally expressed in transgenic plants. We compared the phenotypic traits and physiological characteristics of the non-transgenic line (wild-type, WT) and transgenic lines under different concentrations of NaCl and NaHCO3. The growth of the WT was inhibited severely, and even death was observed, but the transgenic lines were just slightly inhibited. The proline and superoxide dismutase (SOD) contents of the transgenic lines were significantly higher than those of the WT (P<0.05), and the relative membrane permeability of the transgenic lines were significantly lower than those of the WT under salt stress. More H2O2 accumulated in the leaves of the WT compared to in those of transgenic lines. This result showed that rgMT was expressed in M. sativa, and the transgenic lines had a greater salinity tolerance than the WT.