Overexpression of the GmDREB2 gene increases proline accumulation and tolerance to drought stress in soybean plants

The dehydration responsive element binding (DREB) is a plant protein subfamily expressed when soybean plants face abiotic stresses. These DREB proteins are also considered to activate the transcription of drought-resistant genes. In this study, we present the determined results of relationships between overexpression of Glycine max DREB2 (GmDREB2) with the transcription level of Glycine max pyrroline-5-carboxylate synthetase (GmP5CS) gene, proline accumulation and drought tolerant ability transgenic soybean plants as the basis for selection of transgenic lines with high drought tolerance. GmDREB2 was inserted into a plant transgenic vector and the 35S-GmDREB2-cmyc construct was transferred into the soybean plants by Agrobacterium-mediated transformation. Recombinant GmDREB2 protein with a molecular weight of approximately 20 kDa was expressed in four transgenic soybean lines in the T1 generation. The GmP5CS gene was shown to have significantly (P<0.05) increased expression in the T2 transgenic soybean lines and higher than compared to non-transgenic plants with considering both in well watered condition and stressed conditions were from 1.06 to 1.31-fold and 1.37 to 1.95-fold, respectively. The proline content of four transgenic soybean lines increased 155.81% to 187.42 % after five days in drought-stress conditions and increased from 180.52 % to 233.74 % after nine days under drought-stress conditions (P<0.05). Therefore, the overexpression of GmDREB2 resulted in increasing transcription level of P5CS gene, proline accumulation and drought-stress tolerance of the transgenic soybean plants. The GmDREB2 transformation into soybean plants was confirmed by the results of genetically modified lines in the T2 generation (T2-1, T2-6, T2-7, and T2-8) with higher drought tolerant ability than those of non-transgenic plants.