【摘要】 紫云英根瘤菌SR72和76531两菌株都有相同的两个质粒,其分子量分别为200 Md和80Md。它们各自的HC Nod^-变株都消失了其中的200 Md质粒,但尚一致地保留着80Md的质粒,紫云英根瘤菌的结瘤功能显然与该200 Md质粒有极为密切的关系。Inc P1组的质粒能以10^-4/每个受体细胞的频率转入紫云英根瘤菌,而在紫云英根瘤菌之间的转移频率为10^-4—10^-5。紫云英根瘤菌的结瘤功能,可以通过P1组的质粒诱动,从野生型Nod⁺菌株转移到HC Nod^-受体菌株中,甚至转移到消除了Ti质粒的土壤农杆菌中,能使紫云英结瘤。这些有结瘤能力的Nod⁺接合子,其抗药性标记完全与Nod^-受体菌一样,但其质粒电泳图谱,既不同于供体,也不同于受体,缺供体中对应的200 Md大质粒带,比受体的却又多了一40 Md的质粒带。更多还原

【Abstract】 Zhizobium astragalii strain SR72 and strain 76531 both carry similar two plasmids with the molecular weight 200 Md and 80 Md detected by agarose gel electrophoresis. In all non-nodulating (HC Nod") mutants from these strains, the 200Md plasmid was missing but the 80 Md plasmid was maintained uniformly. This 200 Md plasmid is suggested to be the Sym plasmid carrying the genes for nodulating plants of A. sinicus. cus.The IncP1 group plasmid can be transferred into R. astragalii from E.coli or Pseudomonas aeruginosa donors at the frequencies of 10-4/per recipient cell and transferred between R. astragali strains at the frequencies of 10-4-10-5.The determinants for nodulating A. sinicus can be mobilized by the IncP1 group plasmids, from the Nod+ strains to the HC Nod- recipients and to a Ti plasmid cured strain of Agrdbacterium tumefaciens Atl36. The Rhizobium transconjugants regain the nodulation function and induced normal nodules on the roots of A. sinicus. The transconjugants of Atl36 incited small Fix- pseudonodules on the roots of A. sinicus.更多还原