LlDREB1G, a novel DREB subfamily gene from Lilium longiflorum, can enhance transgenic Arabidopsis tolerance to multiple abiotic stresses

In plants, most DREB1s/CBFs proteins with a single AP2/ERF domain participate in responses to abiotic stresses. Here, we cloned a DREB subfamily gene from Lilium longiflorum (designated as LlDREB1G). Sequence analyses revealed that it is composed of 219 amino acids, and contains an AP2/ERF domain, a putative nuclear localization signal (NLS), a DSAW/R and LWSY motif. LlDREB1G, which was localized to the nucleus, showed strongly induced expression under low temperature, and was also stimulated by mechanical agitation, heat shock, ABA and H2O2 stresses. Moreover, the LlDREB1G gene had an obvious circadian rhythm and organ specificity in expression. The LlDREB1G transcription factor was functional in the heterologous system (Arabidopsis). Transgenic Arabidopsis plants with higher transcription of LlDREB1G gene exhibited increased acquired thermotolerance and resistance to freezing and dehydration stresses. Besides, the transgenic seeds were insensitive to exogenous ABA treatment than those of the wild type (WT) in germination experiments. Compared with the WT seedlings, the seedlings of transgenic Arabidopsis overexpressing LlDREB1G showed strongly upregulated expression of stress-related genes after cold, drought or acclimation to heat shock treatments. Furthermore, overexpression of LlDREB1G increased the proline levels and survival rates, but decreased the electrolyte leakage and H2O2 accumulation in the transgenic plants after freezing, dehydration and high temperature treatments. These results imply that LlDREB1G gene may be involved in the responses to multiple abiotic stresses in an ABA-dependent and -independent manner.