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生物3型葡萄根癌农杆菌MI3—2有很窄的宿主范围,除了葡萄外,只对少数植物能致瘤。我们先前的研究曾观察到,MI3—2菌株的DNA与广宿主根癌农杆菌A348的PTiA6质粒毒力区virA基因座和T—DNA的tms基因不同源。本实验把含有PTiA6质粒T_L—DNA片段及毒力区各基因座(virA,B,G,c,D和E)片段的粘粒(cosmid),通过三菌接合引入MI3—2菌株,组成局部二倍体,使之与MI3—2Ti质粒中相对应的基因互补。用这种转移接合子感染植物表明,引入有T_L—DNA片段或virA基因座的MI3—2,均能使宿主范围有所扩大,并能在落地生根致瘤。本文提出了广宿主virA基因对根癌农杆菌宿主范围的作用。
Biological type 3 Agrobacterium tumefaciens MI3-2 has a very narrow host range, with the exception of grapes, which can produce tumors only for a few plants. Our previous study has observed that the DNA of the MI3-2 strain is not homologous to the tms gene of the viru locus and T-DNA of the PTiA6 plasmid virulence region of Agrobacterium tumefaciens A348. In this experiment, the cosmid containing the fragment of T_L-DNA of PTiA6 and the virulence region (virA, B, G, c, D and E) fragments was introduced into MI3-2 strain Diploid, making it complementary to the corresponding gene in the MI3-2Ti plasmid. Infection of plants with this transfer adapter showed that introduction of MI3-2 with either the T_L-DNA fragment or the virA locus enabled the host range to expand and lead to rooting tumors on the ground. This paper presents the effect of host virA gene on Agrobacterium tumefaciens host range.