Overexpression of NnDREB2, isolated from lotus improves salt tolerance in transgenic Arabidopsis thaliana

DREBs are believed to participate in plant responses to adverse environmental factors by activating down-stream stress-inducible genes. In this study, we isolated an NnDREB2 from a salt-resistant lotus species using RT-PCR and RACE methods. Expression profiling by real-time PCR technique revealed that NnDREB2 enhanced transcriptional level when treated with NaCl and exogenous ABA, and while its expression was not significantly changed with mannitol or 4 degrees C treatments. NnDREB2 was transformed into Arabidopsis with a binary vector (SN1301) construct to identify its function. After selection of 'positive' transgenic plants, transgenic and non-transgenic plants (wild type plants) were treated with 250 mM NaCl. We found that the plants overexpressing NnDREB2 led to higher salt resistance than that of the wild type plants according to their survival rates. In addition, NnDREB2 expression exhibited higher germination rates and better root growth than in control plants on MS medium containing various concentration of NaCl. Down-stream target stress-related genes were also analyzed, and we observed that NnDREB2 overexpression activated stress-responsive genes such as PIP1-2, PIP2-5 and PIP2-7 in transgenic Arabidopsis plants. Totally, our findings suggested that the NnDREB2 participated in an ABA-dependent pathway, and might play an important role in plant for salt stress adaptation by directly binding with the DRE element tnemeto regulate down-stream gene expression in salt-resistant lotus.