CLUSTERING OF NITROGEN-FIXATION (NIF) GENES IN RHIZOBIUM-MELILOTI
CLUSTERING OF NITROGEN-FIXATION (NIF) GENES IN RHIZOBIUM-MELILOTI
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DOI：
10.1128/jb.149.1.221-228.1982
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发表时间：
1982-01-01
影响因子：
3.2
通讯作者：
HELINSKI, DR
中科院分区：
文献类型：
--
作者：
CORBIN, D;DITTA, G;HELINSKI, DR
克隆了一个与肺炎克雷伯菌氮酶结构基因同源的17.3千碱基区域。确定了同源程度的极限。该区域的转座子突变证实其含有功能性nif基因。一些转座子插入导致共生表型缺陷，而其他转座子插入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3种不同的基因表达单位。将苜蓿根瘤和无性生长根瘤菌的RNA与克隆的DNA进行杂交，发现该区域至少有11.1千碱基的转录活跃，并且转录是共生状态下特异性的。
A cloned 17.3-kilobase region of the R. 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 positions of insertions yielding these 2 phenotypic classes suggested that at least 3 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 were transcribed actively and that transcription was specific for the symbiotic state.