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 TaABP 1 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.
CAO Xin-youCHEN MingXU Zhao-shiCHEN Yao-fengLI Lian-chengYU Yue-huaLIU Yang-naMAYou-zhi
以耐盐性较强的大豆(Glycine max L.)品种铁丰8号为试验材料,克隆到1个A亚族bZIP类转录因子基因,命名为GmAREB(Glycine max ABA responsive element binding protein)。该基因由1317个核苷酸组成,编码439个氨基酸残基,包括4个保守的磷酸化位点区域(C1、C2、C3和C4)、1个核定位信号区(KVVE)和1个bZIP转录因子保守域。聚类分析显示GmAREB蛋白与拟南芥ABF2、水稻OsTRAB1具有较高的同源性,并存在较近的亲缘关系。采用凝胶阻滞实验方法证明GmAREB蛋白与ABRE顺式元件具有体外结合特异性。功能分析结果表明,在干旱胁迫条件下,GmAREB转基因拟南芥的存活率(50%)显著高于野生型(5%);气孔统计分析显示转基因植株的气孔开度(0.8μm)明显比对照开度小(2.6μm)。氧化胁迫结果显示GmAREB转基因拟南芥在甲基紫精溶液中叶绿素含量比野生型高(7.3mg g-1 FW)。转基因拟南芥RT-PCR分析表明,GmAREB基因过表达能够增强下游胁迫相关基因ABI1、ABI2的表达,抑制气孔开闭相关基因KAT1、KAT2的表达。综上所述,GmAREB基因过表达有效调控了转基因拟南芥下游靶基因表达,加速了气孔关闭,减少了水分蒸发和叶绿素降解,从而提高了转基因拟南芥对干旱、氧化胁迫耐性。
