华癸中生根瘤菌HN3015非共生质粒pMhHN3015a的不相容性行为

摘要

The Tn5-mob-sacB-labeled non-symbiotic pMhHN3015a of Mesorhizobium huakuii HN3015 was respectively transferred into M. huakuii HN308SR and 7653R-1SR by tri-parent mating. Two transconju-gants, HN308SRN29 and 7653R-1SRN29 were obtained. The plasmid profiles of HN308SRN29 showed that pMhHN308b of HN308SR were cured. The results implied that pMhHN3015a and pMhHN308b were incompatible. However, the results from plasmid curing tests of HN308SRN29 showed that labeled plasmid cured derivative of HN308SRN29 could not be obtained. Since the sizes of pMhHN3015a and pMhHN308a were almost the same and their positions in agarose gels were difficult to distinguished, so that two plasmids might have been recombined and transposon Tn5 transferred into the chromosome. The plasmid profiles of transconjugant 7653R-1SRN29 showed that pMhHN3015a could coexist with pMh7653Ra. Furthermore, the results from plasmid curing tests of 7653R-1SRN29 showed that two mutants, 7653R-1SRN29D-A and 7653R-1SRN29D-B were obtained. The plasmid profiles showed that 7653R-1SRN29D-A and 7653R-1SRN29D-B lost pMhHN3015a, and that 7653R-1SRN29D-B showed an additional plasmid that was named p76H4. Results from plant nodulation tests showed that HN308SRN29 lost nodulation ability. But nodulation of 7653R-1SRN29 was enhanced. 7653R-1SRN29D-A could only form null nodules. However, 7653R-1SRN29D-B lost its nodulation ability.%采用三亲本杂交将Tn5-mob-sacB标记华癸中生根瘤菌(Mesorhizobium huakuii)HN3015的非共生质粒pMhHN3015a分别导入HN308SR和7653R-1SR,获得2个转移接合子HN308SRN29和7653R-1SRN29.HN308SRN29的质粒图谱显示HN308SR的pMhHN308b被消除,该结果暗示pMhHN3015a和pMhHN308b不相容.然而,HN308SRN29的质粒消除实验未获得标记质粒消除突变株.pMhHN3015a和pMhHN308a的大小相近,仅凭凝胶电泳位置难于区分.pMhHN308a可能因与pMhHN3015a发生了重组,其Tn5亦可能因转座至染色体而不能获得标记质粒消除突变株.7653R-1SRN29的质粒图谱显示pMhHN3015a可与pMh7653Ra共存.但7653R-1SRN29的质粒消除实验获得的2个质粒消除突变株7653R-1SRN29D-A和7653R-1SRN29D-B均消除了pMhHN3015a,而7653R-1SRN29D-B产生了一个新质粒p76H4.植物盆栽结瘤试验结果表明:HN308SRN29失去了结瘤能力,7653R-1SRN29的结瘤能力提高.7653R-1SRN29D-A只能形成少量无效根瘤,7653R-1SRN29D-B却完全丧失了结瘤能力.