Aeschbacher R A, Schrott M, Potrykus I, Saul M W
Institute for Plant Sciences, Developmental Biology, Swiss Federal Institute of Technology, Zürich.
Plant J. 1991 Nov;1(3):303-16.
We have isolated a putative transcription factor gene, PosF21, from Arabidopsis thaliana using an indirect cross-hybridization approach. cDNA clones were isolated which encode single repeating amino acids. Such sequences may function as activation domains in transcription factors and may be indicative for such proteins. The clone PosF21 encodes a region very rich in glutamines. Besides this putative activation domain it encodes a protein sequence which shows all the characteristics of a basic-domain/leucine zipper type of DNA-binding domain. PosF21 is expressed constitutively at a low level in young seedlings and in roots, stems and leaves of mature Arabidopsis plants. A genomic clone of PosF21 was isolated and the gene structure was analyzed. Related sequences in Arabidopsis and a wide range of other plants were detected using the putative DNA-binding domain as a probe in cross-hybridization experiments. Transient transformations in tobacco protoplasts were performed using the beta-glucuronidase (GUS) gene as reporter gene. Approximately 400 bp of the 5' genomic region of PosF21 promote expression of the GUS gene in tobacco protoplasts. Evidence for a regulatory function of PosF21 was obtained since co-expression of the full PosF21 protein or its DNA-binding region alone specifically stimulated GUS gene expression directed from the PosF21 promoter by 6-8-fold.
我们利用间接交叉杂交方法从拟南芥中分离出一个假定的转录因子基因PosF21。分离出的cDNA克隆编码单一重复氨基酸。这样的序列可能在转录因子中起激活结构域的作用，并且可能是这类蛋白质的指示物。克隆PosF21编码一个富含谷氨酰胺的区域。除了这个假定的激活结构域，它还编码一个蛋白质序列，该序列显示出碱性结构域/亮氨酸拉链型DNA结合结构域的所有特征。PosF21在幼苗以及成熟拟南芥植株的根、茎和叶中以低水平组成型表达。分离出PosF21的基因组克隆并分析了基因结构。在交叉杂交实验中，使用假定的DNA结合结构域作为探针，检测了拟南芥和其他多种植物中的相关序列。以β-葡萄糖醛酸酶（GUS）基因作为报告基因，在烟草原生质体中进行了瞬时转化。PosF21 5'基因组区域约400 bp促进烟草原生质体中GUS基因的表达。由于单独共表达完整的PosF21蛋白或其DNA结合区域可特异性刺激由PosF21启动子指导的GUS基因表达6至8倍，因此获得了PosF21具有调控功能的证据。
