Lightfoot D A, Baron A J, Cock J M, Wootton J C
Department of Plant and Soil Science, University of Southern Illinois, Carbondale 62901.
Genetica. 1992;85(2):107-17. doi: 10.1007/BF00120317.
DNA probes from the narG gene of Escherichia coli, which encodes the large polypeptide of respiratory nitrate reductase, show cross-hybridization at low stringency to a single region of the genome of the cyanobacterium Synechococcus PCC6301. This segment of cyanobacterial DNA was cloned as the insert of plasmid pDN1 and characterized. RNA complementary to pDN1 was shown to be substantially more abundant in nitrate grown cells of Synechococcus PCC6301 than in ammonium grown cells, thus parallelling the nitrate induction and ammonium repression of nitrate reductase activity in cultures of this cyanobacterium. A mutant of Synechococcus PCC6301 deficient in nitrate reductase activity was obtained after a potentially mutagenic transformation treatment using pDN1 as a donor. This mutant was restored to the wild type phenotype following stable integrative transformation with pDN1 DNA. Taken together these data suggest that pDN1 might encode a polypeptide of nitrate reductase. pDN1 is distinct from three clones of genes involved in nitrate assimilation that were isolated previously from the related cyanobacterium Synechococcus PCC7942 (Kuhlemeier et al., 1984a, J. Bact. 159, 36-41, and 1984b, Gene 31, 109-116).
来自大肠杆菌narG基因的DNA探针，该基因编码呼吸硝酸盐还原酶的大多肽，在低严谨度下与蓝细菌聚球藻PCC6301基因组的单个区域显示交叉杂交。这段蓝细菌DNA片段被克隆为质粒pDN1的插入片段并进行了表征。与pDN1互补的RNA在聚球藻PCC6301的硝酸盐生长细胞中比在铵生长细胞中明显更丰富，因此与该蓝细菌培养物中硝酸盐还原酶活性的硝酸盐诱导和铵抑制情况相似。在使用pDN1作为供体进行潜在诱变转化处理后，获得了聚球藻PCC6301的硝酸盐还原酶活性缺陷型突变体。用pDN1 DNA进行稳定整合转化后，该突变体恢复为野生型表型。综合这些数据表明，pDN1可能编码硝酸盐还原酶的一种多肽。pDN1与先前从相关蓝细菌聚球藻PCC7942中分离出的三个参与硝酸盐同化的基因克隆不同（库勒迈尔等人，1984年a，《细菌学杂志》159卷，36 - 41页，以及1984年b，《基因》31卷，109 - 116页）。
