George M L, Young J P, Borthakur D
Biotechnology Program, University of Hawaii, Honolulu 96822.
Can J Microbiol. 1994 Mar;40(3):208-15. doi: 10.1139/m94-034.
Rhizobium sp. strain TAL1145 nodulates Leucaena leucocephala and Phaseolus vulgaris, in addition to a wide range of tropical tree legumes. Six overlapping clones that complemented nodulation defects in leucaena and bean rhizobia were isolated and a 40-kb map of the symbiosis region was constructed. The common nod and nifA genes were situated approximately 17 kb apart, with the nodIJ genes in between. These clones enabled a derivative of TAL1145 carrying a partially deleted pSym to form ineffective nodules on both leucaena and bean, and a similar derivative of Rhizobium etli TAL182 to form ineffective nodules on bean. When two representative clones, pUHR9 and pUHR114, were each transferred to wild-type rhizobial strains, they allowed ineffective nodulation by Rhizobium meliloti on both leucaena and bean and by Rhizobium leguminosarum bv. vicia on bean. Transconjugants of R. leguminosarum bv. trifolii formed effective nodules on leucaena and ineffective nodules on bean. Tn5 mutagenesis of the symbiosis region resulted in a variety of nodulation and fixation phenotypes on leucaena and bean. On the basis of 16S rRNA sequences, TAL1145 was found to be distinct from both R. tropici and NGR234, the two groups of leucaena symbionts that were previously described.
根瘤菌属菌株TAL1145除了能与多种热带豆科树木形成根瘤外，还能与银合欢和菜豆形成根瘤。分离出了六个互补银合欢和菜豆根瘤菌结瘤缺陷的重叠克隆，并构建了共生区域的40 kb图谱。常见的结瘤基因和nifA基因相距约17 kb，中间是nodIJ基因。这些克隆使携带部分缺失的共生质粒的TAL1145衍生物在银合欢和菜豆上都能形成无效根瘤，使埃氏根瘤菌TAL182的类似衍生物在菜豆上形成无效根瘤。当两个代表性克隆pUHR9和pUHR114分别转移到野生型根瘤菌菌株时，它们使苜蓿根瘤菌在银合欢和菜豆上以及豌豆根瘤菌蚕豆生物型在菜豆上形成无效根瘤。三叶草根瘤菌的接合子在银合欢上形成有效根瘤，在菜豆上形成无效根瘤。共生区域的Tn5诱变导致在银合欢和菜豆上出现多种结瘤和固氮表型。基于16S rRNA序列，发现TAL1145与先前描述的两组银合欢共生菌热带根瘤菌和NGR234都不同。
