Department of Biological Sciences, Stanford University, 94305, Stanford, CA, USA.
Planta. 1987 Jul;171(3):289-301. doi: 10.1007/BF00398674.
We have used spot-inoculation and new cytological procedures to observe the earliest events stimulated in alfalfa (Medicago sativa L.) roots by Rhizobium meliloti. Roots were inoculated with 1-10 nl of concentrated bacteria, fixed in paraformaldehyde, and after embedding and sectioning stained with a combination of acridine orange and DAPI (4'-6-diamidino-2-phenylindole hydrochloride). Normal R. meliloti provoke cell dedifferentiation and mitosis in the inner cortex of the root within 21-24 h after inoculation. This activation of root cells spreads progressively, leading to nodule formation. In contrast, the R. meliloti nodA and nodC mutants do not stimulate any activation or mitosis. Thus the primary and earliest effect of Rhizobium nod gene action is plant cellular activation. A rapid, whole-mount visualization by lactic acid shows that the pattern of nodule form varies widely. Some R. meliloti strains were found to be capable of stimulating on alfalfa roots both normal nodules and a "hybrid" structure intermediate between a nodule and a lateral root.
我们使用点接种和新的细胞学程序来观察苜蓿（Medicago sativa L.）根中根瘤菌（Rhizobium meliloti）刺激的最早事件。将浓缩细菌接种到 1-10 nl 根中，用多聚甲醛固定，然后包埋和切片，并用吖啶橙和 DAPI（4'-6-二脒基-2-苯基吲哚盐酸盐）组合染色。正常的 R. meliloti 在接种后 21-24 小时内引发内皮层细胞的去分化和有丝分裂。这种根细胞的激活逐渐扩散，导致形成根瘤。相比之下，R. meliloti nodA 和 nodC 突变体不会刺激任何激活或有丝分裂。因此，根瘤菌 nod 基因作用的最初和最早效应是植物细胞的激活。乳酸的快速全株可视化显示，根瘤形成的模式差异很大。发现一些 R. meliloti 菌株能够在苜蓿根上刺激正常根瘤和介于根瘤和侧根之间的“杂交”结构。
