Better M, Lewis B, Corbin D, Ditta G, Helinski D R
Cell. 1983 Dec;35(2 Pt 1):479-85. doi: 10.1016/0092-8674(83)90181-2.
Symbiotic nitrogen fixation by Rhizobium meliloti requires the developmentally specific expression of certain bacterial genes. One set of these genes encodes the subunits of nitrogenase, the enzyme responsible for the reduction of atmospheric dinitrogen to ammonia, and another set consists of closely linked genes also essential for nitrogen fixation. Examination of promoter and probable regulatory regions for these gene sets has revealed extensive DNA sequence conservation for more than 160 bp upstream of the respective transcription start points. Three such promoter regions have been identified in the nitrogen fixation (nif) gene cluster of R. meliloti strain 102F34. Using one of these promoter regions as a hybridization probe, three additional sequences were found in the genome of this strain. The DNA of other R. meliloti strains and Rhizobium species were also examined for homology to the symbiotically regulated promoters of R. meliloti 102F34. DNA sequences homologous to these R. meliloti promoters were found among diverse rhizobia, and in at least some cases were associated with nif genes.
苜蓿根瘤菌的共生固氮需要某些细菌基因的发育特异性表达。其中一组基因编码固氮酶的亚基，该酶负责将大气中的二氮还原为氨，另一组由紧密相连的基因组成，这些基因对固氮也至关重要。对这些基因集的启动子和可能的调控区域进行检查后发现，在各自转录起始点上游超过160 bp的区域存在广泛的DNA序列保守性。在苜蓿根瘤菌102F34菌株的固氮（nif）基因簇中已鉴定出三个这样的启动子区域。使用这些启动子区域之一作为杂交探针，在该菌株的基因组中发现了另外三个序列。还检查了其他苜蓿根瘤菌菌株和根瘤菌属物种的DNA与苜蓿根瘤菌102F34的共生调控启动子的同源性。在不同的根瘤菌中发现了与这些苜蓿根瘤菌启动子同源的DNA序列，并且在至少某些情况下与nif基因相关。
