Wong C H, Pankhurst C E, Kondorosi A, Broughton W J
J Cell Biol. 1983 Sep;97(3):787-94. doi: 10.1083/jcb.97.3.787.
We examined expression of the megaplasmid pRme41b of Rhizobium meliloti in two different Rhizobium sp. Strains and in Agrobacterium tumefaciens. Transfer of pRme41b into these bacteria was facilitated by insertion of a recombinant plasmid coding for mobilization functions of RP4 into the nif region (Kondorosi, A., E. Kondorosi, C.E. Pankhurst, W. J. Broughton, and Z. Banfalvi, 1982, Mol. Gen. Genet., 188:433-439). In all cases, transconjugants formed nodule-like structures on the roots of Medicago sativa. These structures were largely composed of meristematic cells but they were not invaded by bacteria. Bacteria were found only within infection threads in root hairs, and within intercellular spaces of the outermost cells of the structures. The donor strain of R. meliloti containing pAK11 or pAK12 in pRme41b initially produced nodules on M. sativa that did not fix nitrogen (Fix-). In these nodules, bacteria were released from infection threads into the host cells but they did not multiply appreciably. Any bacteroids formed degenerated prematurely. In some cases, however, reversion to a Fix+ phenotype occurred after 4 to 6 wk. Bacteria released into newly infected cells in these nodules showed normal development into bacteriods.
我们检测了苜蓿根瘤菌的大质粒pRme41b在两种不同的根瘤菌菌株以及根癌农杆菌中的表达情况。通过将编码RP4迁移功能的重组质粒插入固氮基因区域，促进了pRme41b向这些细菌的转移（孔多罗西，A.，E. 孔多罗西，C.E. 潘克赫斯特，W.J. 布劳顿，以及Z. 班法尔维，1982年，《分子遗传学与普通遗传学》，188:433 - 439）。在所有情况下，接合子在紫花苜蓿的根上形成了类似根瘤的结构。这些结构主要由分生细胞组成，但未被细菌侵染。细菌仅存在于根毛中的侵染丝内，以及这些结构最外层细胞的细胞间隙中。在pRme41b中含有pAK11或pAK12的苜蓿根瘤菌供体菌株最初在紫花苜蓿上产生不固氮的根瘤（Fix-）。在这些根瘤中，细菌从侵染丝释放到宿主细胞中，但它们并未显著增殖。形成的任何类菌体都过早退化。然而，在某些情况下，4至6周后会恢复为固氮阳性（Fix+）表型。在这些根瘤中释放到新感染细胞中的细菌表现出正常发育为类菌体的过程。
