Walden R, Hayashi H, Lubenow H, Czaja I, Schell J
Max Planck Institut für Züchtungsforschung, Köln, Germany.
EMBO J. 1994 Oct 17;13(20):4729-36. doi: 10.1002/j.1460-2075.1994.tb06798.x.
We describe the characterization of axi 1, a tobacco gene isolated by activation T-DNA tagging which apparently plays a role in auxin action. Upon deregulated expression, axi 1 confers on protoplasts the ability to grow in culture not only in the absence of auxin but also in high auxin concentrations where maximal frequencies of cell division are not observed in wild-type protoplasts. In wild-type plants axi 1 is transcribed principally in root tissue. In the tagged plant line, axi 159, axi 1 RNA can be detected in all tissues tested. Freshly isolated wild-type protoplasts require auxin for the accumulation of detectable levels of axi 1 transcript and this precedes maximal levels of cell division. In contrast, axi 1 RNA appears in protoplasts isolated from axi 159 plants in the absence of auxin. axi 1 was localized to 6.2 kb of plant genomic DNA flanking the right T-DNA border sequence. axi 1 is interrupted by nine introns and in tobacco it is a member of a small gene family. Database searching reveals no similarity within the coding region with other genes. Sequences within the fourth intron are similar to those located in the non-coding regions of other plant genes, some of which are known to be auxin inducible. A DNA fragment containing the conserved sequence acts as an auxin responsive element in transient expression assays in wild-type protoplasts and this response is higher in axi 159 protoplasts. This suggests that auxin induced axi 1 expression may be mediated by a region contained within an intron sequence and that the axi 1 product might play a role in this induction.
我们描述了axi 1的特性，axi 1是通过激活T-DNA标签分离得到的一个烟草基因，它显然在生长素作用中发挥作用。在表达失调时，axi 1赋予原生质体在培养中生长的能力，不仅在没有生长素的情况下，而且在高生长素浓度下也能生长，而在野生型原生质体中未观察到细胞分裂的最大频率。在野生型植物中，axi 1主要在根组织中转录。在标记的植株系axi 159中，axi 1 RNA可在所有测试组织中检测到。新鲜分离的野生型原生质体需要生长素才能积累可检测水平的axi 1转录本，且这发生在细胞分裂的最大水平之前。相比之下，在没有生长素的情况下，axi 1 RNA出现在从axi 159植株分离的原生质体中。axi 1定位于右T-DNA边界序列侧翼的6.2 kb植物基因组DNA中。axi 1被9个内含子打断，在烟草中它是一个小基因家族的成员。数据库搜索显示，其编码区域与其他基因没有相似性。第四个内含子中的序列与其他植物基因非编码区域中的序列相似，其中一些已知是生长素诱导型的。在野生型原生质体的瞬时表达试验中，包含保守序列的DNA片段可作为生长素反应元件，并且在axi 159原生质体中的这种反应更高。这表明生长素诱导的axi 1表达可能由内含子序列中的一个区域介导，并且axi 1产物可能在这种诱导中发挥作用。
