Corbin D, Ditta G, Helinski D R
J Bacteriol. 1982 Jan;149(1):221-8. doi: 10.1128/jb.149.1.221-228.1982.
A cloned 17.3-kilobase region of the Rhizobium meliloti genome with homology to the Klebsiella pneumoniae nitrogenase structural genes was studied. Limits on the extent of homology were determined. Transposon mutagenesis of this region of the genome verified that it contained functional nif genes, Some transposon insertions resulted in a defective symbiotic phenotype, whereas others had no noticeable effect on symbiotic competence. The relative position of insertions yielding these two phenotypic classes suggested that at least three distinct units of gene expression are present in this region. Hybridization of RNA from alfalfa root nodules and from vegetatively grown Rhizobium to this cloned DNA showed that at least 11.1 kilobases of the region was transcribed actively and that transcription was specific for the symbiotic state.
对根瘤菌基因组中一个与肺炎克雷伯菌固氮酶结构基因具有同源性的17.3千碱基克隆区域进行了研究。确定了同源性的范围界限。对该基因组区域进行转座子诱变证实它含有功能性的固氮基因。一些转座子插入导致共生表型缺陷，而另一些对共生能力没有明显影响。产生这两种表型类别的插入的相对位置表明该区域至少存在三个不同的基因表达单元。来自苜蓿根瘤和营养生长的根瘤菌的RNA与该克隆DNA的杂交表明该区域至少11.1千碱基被活跃转录，并且转录对共生状态具有特异性。
