Baumann K, De Paolis A, Costantino P, Gualberti G
Istituto Pasteur Fondazione Cenci Bolognetti, Dipartimento di Genetica e Biologia Molecolare, Università La Sapienza, Piazzale Aldo Moro 5, 00185 Rome, Italy.
Plant Cell. 1999 Mar;11(3):323-34. doi: 10.1105/tpc.11.3.323.
The Dof proteins are a large family of plant transcription factors that share a single highly conserved zinc finger. The tobacco Dof protein NtBBF1 was identified by its ability to bind to regulatory domain B in the promoter of the rolB oncogene. In this study, we show that the ACT T TA target sequence of NtBBF1 in domain B is necessary for tissue-specific expression of rolB. beta-Glucuronidase (GUS) activity of tobacco plants containing a rolB promoter-GUS fusion with a mutated NtBBF1 target sequence within domain B is almost completely suppressed in apical meristems and is severely abated in the vascular system. The ACT T TA motif is shown here also to be one of the cis-regulatory elements involved in auxin induction of rolB. The pattern of NtBBF1 expression in plants is remarkably similar to that of rolB, except in mesophyll cells of mature leaves, in which only NtBBF1 expression could be detected. Ectopic expression of rolB in mesophyll cells was achieved by particle gun delivery if the NtBBF1 binding sequence was intact. These data provide evidence that in the plant, a Dof protein DNA binding sequence acts as a transcriptional regulatory motif, and they point to NtBBF1 as the protein involved in mediating tissue-specific and auxin-inducible expression of rolB.
Dof蛋白是植物转录因子中的一个大家族，它们共享一个高度保守的锌指结构。烟草Dof蛋白NtBBF1是通过其与rolB癌基因启动子中调控域B的结合能力而被鉴定出来的。在本研究中，我们表明，NtBBF1在域B中的ACT T TA靶序列对于rolB的组织特异性表达是必需的。在域B内具有突变的NtBBF1靶序列的含有rolB启动子 - GUS融合体的烟草植株的β - 葡萄糖醛酸酶（GUS）活性在顶端分生组织中几乎完全被抑制，并且在维管系统中严重减弱。在此还表明，ACT T TA基序也是参与生长素诱导rolB的顺式调控元件之一。除了在成熟叶片的叶肉细胞中只能检测到NtBBF1的表达外，NtBBF1在植物中的表达模式与rolB的表达模式非常相似。如果NtBBF1结合序列完整，通过粒子枪轰击可在叶肉细胞中实现rolB的异位表达。这些数据提供了证据，证明在植物中，一个Dof蛋白DNA结合序列作为转录调控基序，并且它们指出NtBBF1是参与介导rolB的组织特异性和生长素诱导表达的蛋白质。
