紫云英根瘤菌共同结瘤基因nodA和nodBC的核苷酸序列

以~(32)p标记的苜蓿根瘤菌(Rhizobium meliloti)2.3kb nod DNA作探针,从紫云英根瘤菌(Rhizobium huakuii即R. astragali)159基因文库中分离到一株能与探针DNA呈阳性反应的克隆pRaN109。同源DNA-DNA杂交及DNA序列分析表明:pRaN109DNA的9kb EcoRI片段上携带了nodD_1BC基因,pRaN109 NDA的18kb EcoRI片段上携带了nodD_2A基因。共同结瘤基因nodA与nodBC两者相距6.7kb。在nodA基因和nodBC基因的上游都存在有结瘤盒(nod box)。与来自不同种属的菌株所报告的结果相比较,紫云英根瘤菌159中的共同结瘤基因有着明显不同的组合。

NUCLEOTIDE SEQUENCE OF THE RHIZOBIUM HUAKUII COMMON NODUTION GENES nodA AND nodBC

An another clone pRaN109 which contains nod genes was isolated and identified from the clone bank of R huakuii 159 DNA using the 32P-labeled 2.3kb R meliloti nod DNA fragment as a hybridization probe. Analysis of homologous DNA-DNA hybridization and nucleotide sequence indicated that the 9kb EcoRI fragment of pRaN109 DNA carried the nodD1BC genes and the 18kb EcoRI fragment of pRaN109 DNA contained nodD2A genes. The common nodA gene was separated by 6.7kb from the nodBC genes. Both the nodA and bodB-nodC cistrons showed nod box upstream of these genes. Nucleotide sequence analysis of the genes describes a obviously different organization of common nod genes in R. huakuii 159 compared with that reported for most of the strains from different genera described up to now.