R－prime质粒pMN53在不同根瘤菌中的稳定性

ｐＭＮ５３是以ｐＭＮ２为载体克隆有菜豆根瘤菌（Ｒｈｉｚｏｂｉｕｍｌｅｇｕｍｉｌｏｓａｒｕｍｂｖ．ｐｈａｓｅｏｌｉ）共生基因的Ｒ－ｐｒｉｍｅ质粒，将ｐＭＮ５３接合转移到快生型大豆根瘤菌（Ｒｈｉｚｏｂｉｕｍｆｒｅｄｉｉ）Ｂ５２，慢生型大豆根瘤菌（Ｂｒａｄｙｒｈｉｚｏｂｉｕｍｊａｐｏｎｉｃｕｍ）２２１０以及紫云英根瘤菌（Ｒｈｉｚｏｂｉｕｍｈｕａｋｕｉｉ）７６５３Ｒ后，分别考察了ｐＭＮ５３在３种转移接合子中的稳定性。结果表明由ｐＭＮ５３携带的卡那霉素抗性（Ｋｍｒ）在３种供试菌株中都能稳定传代，但电泳分析都只能检测到载体质粒ｐＭＮ２，载体上所携带的外源基因脱落。用Ｔｎ５为探针进行的斑点杂交，结果证明转移接合子２２１０Ｐ仍带有转座子Ｔｎ５。

STABILITY OF R-PRIME PLASMID pMN53 IN DIFFERENT RHIZOBIUM STRAINS

R-prime plasmid pMN53 consists of the symbiotic genes of Rhizobium leguminosarum bv. phaseoli RCR 3 622 and the vector pMN2. It was transfered into three different rhizobium strains(Rhizobium fredii B52, Bradyrhizobium japonicum 2210 and Rhizobium huakuii 7653R), and the stability of pMN53 was tested. The Kmr marker carried by Tn5 in the inserted DNA fragment of pMN53 was very stable, but only the vector pMN2 could be detected by electrophoresis in the three kinds of transconjugants. It was proved by dot hybridization that Tn5 still existed in transconjugant 2210P.