2ND SYMBIOTIC MEGAPLASMID IN RHIZOBIUM-MELILOTI CARRYING EXOPOLYSACCHARIDE AND THIAMINE SYNTHESIS GENES
2ND SYMBIOTIC MEGAPLASMID IN RHIZOBIUM-MELILOTI CARRYING EXOPOLYSACCHARIDE AND THIAMINE SYNTHESIS GENES
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DOI：
10.1128/jb.167.1.66-72.1986
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发表时间：
1986-07-01
影响因子：
3.2
通讯作者：
SIGNER, ER
中科院分区：
文献类型：
--
作者：
FINAN, TM;KUNKEL, B;SIGNER, ER
利用物理和遗传数据，我们已经证明，苜蓿根瘤菌Su 47具有共生megaplasma，pRmeSU 47 b，除了先前描述的nif-megaplasma pRmeSU 47 a。该质粒包括参与胞外多糖（exo）合成的四个基因座以及参与硫胺素生物合成的两个基因座。以前已经证明，exo基因座处的突变会导致缺乏感染线（Inf-）和不能固氮（Fix-）的结节的形成。因此，这两种大质粒都含有参与固氮根瘤形成的基因。在其他两个外切位点的突变不位于任何巨质粒。为了移动大质粒，将质粒RK 2的oriT插入其中。在苜蓿上，含有pRmeSU 47 A的根癌土壤杆菌菌株诱导了明显的根毛卷曲，而没有感染线和固定结节，如其他人所报道的。没有观察到这种植物表型随A.同时含有pRmeSU 47 a和pRmeSU 47 b巨质粒的根瘤菌菌株和仅含有pRmeSU 47 b的菌株不能卷曲根毛或形成根瘤。
Using physical and genetic data, we have demonstrated that Rhizobium meliloti Su47 has a symbiotic megaplasmid, pRmeSU47b, in addition to the previously described nod-nif megaplasmid pRmeSU47a. This plasmid includes four loci involved in exopolysaccharide (exo) synthesis as well as two loci involved in thiamin biosynthesis. Mutations at the exo loci have previously been shown to result in the formation of nodules which lack infection threads (Inf-) and fail to fix nitrogen (Fix-). Thus, both megaplasmids contain genes involved in the formation of nitrogen-fixing root nodules. Mutations at two other exo loci were not located on either megaplasmid. To mobilize the megaplasmids, the oriT of plasmid RK2 was inserted into them. On alfalfa, Agrobacterium tumefaciens strains containing pRmeSU47A induced marked root hair curling with no infection threads and Fix- nodules, as reported by others. This plant phenotype was not observed to change with A. tumefaciens strains containing both pRmeSU47a and pRmeSU47b megaplasmids, and strains containing pRmeSU47b alone failed to curl root hairs or form nodules.