Isolation and Functional Analysis of the bZIP Transcription Factor Gene TaABP1 from a Chinese Wheat Landrace

In plants, basic leucine zipper (bZIP) transcription factors play important roles in regulatory processes, including stress response, pathogenic defense and light response as well as organ and tissue differentiation. Chinese wheat landrace Pingyaoxiaobaimai (PYXBM), an original parent of drought tolerant wheat varieties grown in northern China, is significantly tolerant to abiotic stresses such as drought, cold and nutrient deficiencies. In order to isolate key stress-responsive genes and then improve stress tolerances of conventional varieties, a bZIP transcription factor gene was isolated from a cDNA library of drought-treated PYXBM using the in situ plaque hybridization method, and was designated as Triticum aestivum L. abscisic acid (ABA)-responsive element binding protein 1 (TaABP1). It encodes 372 amino acids, and contains three conserved domains (C1-C3) in the N terminal and a bZIP domain in the C terminal which is a typical protein structure for the group member of bZIP family. Transcriptional activation analysis showed that TaABP1 activated the expression of downstream reporter genes in yeast without ABA application. TaABP1 protein fused with green fluorescent protein (GFP) demonstrated that the localization of TaABP1 protein is in the nucleus. Expression pattern assays indicated that TaABP1 was strongly induced by ABA, high salt, low temperature and drought, and its expression was stronger in stems and leaves than in the roots of wheat. Furthermore, overexpression of TaABP1 in tobacco showed significant improvement of drought tolerance. Data suggested that TaABP1 may be a good candidate gene for improving stress tolerance of wheat by genetic transformation and elucidation of the role of this gene will be useful for understanding the mechanism underlying drought tolerance of Chinese wheat landrace PYXBM.