Novel inducible promoter DREB1G cloned from date palm exhibits high fold expression over AtRD29 to drought and salinity stress

Right and timely expression of the stress regulatory genes is required for plants to compete against abiotic stresses; it necessitates the isolation and characterization of stress-responsive promoters for improving crops' tolerance to abiotic stresses. Dehydration Responsive Element Binding (DREB) regulates the expression of numerous stress-responsive genes in plants and leads an inevitable role in the adaptation of plants to abiotic stresses. In this study, the promoter region of Phoenix dactylifera (Date palm, a major fruit crop of the arid region) PdDREB1G gene was isolated and characterized for the first time. A comparison of the activity of two promoter fragments, 880 bp (DS) and 1.6 kb (DF) of PdDREB1G to AtRD29A was performed. Histochemical assay displayed remarkable GUS staining and RT-qPCR analysis confirmed the induction of GUS expression in T₃ plants of transformed tobacco subjected to different abiotic stresses. Furthermore, compared with the widely used AtRD29A promoter, the relative expression of GUS in leaves by DS and DF was three and twofold higher under salt stress, respectively, while it was twofold in polyethylene glycol (PEG) and abscisic acid (ABA) for DS. Under SA stress, DF and DS displayed 1.5 and onefold expression in leaves, respectively. In the root, DS showed a fourfold increased expression in salt, threefold in PEG and ABA, and twofold in SA. Hence, the DS promoter characterized in the present study becomes a choice over RD29A for abiotic stress responses and is useful to develop stress-tolerant transgenic plants by inducing the expression of stress-inducible genes on stress.