Transcription factor NnDREB1 from lotus improved drought tolerance in transgenic Arabidopsis thaliana

Dehydration responsive element binding factor (DREB) is believed to be a stress-tolerance enhancer in plants. In the present study, a cold-binding factor (CBF)/DREB homologous gene NnDREB1 (XP_010242642.1) was isolated from lotus roots using rapid amplification of cDNA ends (RACE) and reverse transcription (RT)-PCR methods. Analysis of the deduced amino acid sequence and phylogeny classified NnDREB1 into the A-1 group of the DREB1 subfamily. Expression profiling using a quantitative PCR method revealed that NnRDEB1 was significantly induced by NaCl, mannitol, and polyethylene glycol, but not by low temperature and abscisic acid. To evaluate function of NnRDEB1, Arabidopsis thaliana was transformed with the NnDREB1 gene in a binary vector construct. The transgenic plants exhibited higher resistance to drought compared with the wild-type plants in terms of survival rates, dry and fresh masses, and chlorophyll content. In addition, overexpression of NnDREB1 resulted in higher germination rates compared with the wild type plants on MS medium containing mannitol. The expressions of downstream target stressrelated genes, including cold-regulated15B (COR15B), rare cold inducible 2B (RCI2B) and repeat domain 26 (RD26), were activated in the transgenic plants. Taken together, the results suggest that NnDREB1 might be an important protein in lotus root drought tolerance.