Selvaraj G, Iyer V N
J Bacteriol. 1984 May;158(2):580-9. doi: 10.1128/jb.158.2.580-589.1984.
Transposon Tn5 conferred streptomycin resistance on different strains of Rhizobium meliloti, Rhizobium leguminosarum, and Rhizobium trifolii but not on Escherichia coli. A gene (str) specifying this phenotype has been identified and localized on the physical and genetic map of Tn5. It is transcribed from the promoter of neo, the gene that encodes neomycin phosphotransferase. The str gene is downstream from neo in a single transcriptional unit, as revealed by molecular cloning of different segments of Tn5 and by cloning of the neo-str region of Tn5 downstream from a lac promoter. Fusion of the SalI-generated rightward segment of Tn5 (devoid of neo) to a part of a tetracycline resistance gene, tet, in a plasmid or downstream from a lac promoter in a plasmid resulted in significant levels of streptomycin resistance in an R. meliloti host, suggesting that the str gene product can function independent of neomycin phosphotransferase. A natural isolate of R. meliloti that does not express Tn5-associated streptomycin resistance has been identified. We have used the str of Tn5 as a genetic marker in Rhizobium spp.
转座子Tn5赋予了苜蓿根瘤菌、豌豆根瘤菌和三叶草根瘤菌的不同菌株链霉素抗性，但没有赋予大肠杆菌链霉素抗性。一个指定这种表型的基因（str）已被鉴定并定位在Tn5的物理图谱和遗传图谱上。它是从编码新霉素磷酸转移酶的基因neo的启动子转录而来的。如通过Tn5不同片段的分子克隆以及通过将Tn5的neo-str区域克隆到lac启动子下游所揭示的，str基因在一个单一转录单元中位于neo的下游。在质粒中，将由SalI产生的Tn5的向右片段（不含neo）与四环素抗性基因tet的一部分融合，或者在质粒中与lac启动子下游的tet融合，在苜蓿根瘤菌宿主中产生了显著水平的链霉素抗性，这表明str基因产物可以独立于新霉素磷酸转移酶发挥作用。已鉴定出一种不表达与Tn5相关的链霉素抗性的苜蓿根瘤菌自然分离株。我们已将Tn5的str用作根瘤菌属中的遗传标记。
