Laplaze L, Duhoux E, Franche C, Frutz T, Svistoonoff S, Bisseling T, Bogusz D, Pawlowski K
Physiologie Cellulaire et Moléculaire des Arbres, Laboratoire GeneTrop, IRD, Montpellier, France.
Mol Plant Microbe Interact. 2000 Jan;13(1):107-12. doi: 10.1094/MPMI.2000.13.1.107.
Recent phylogenetic studies have implied that all plants able to enter root nodule symbioses with nitrogen-fixing bacteria go back to a common ancestor (D.E. Soltis, P.S. Soltis, D.R. Morgan, S.M. Swensen, B.C. Mullin, J.M. Dowd, and P.G. Martin, Proc. Natl. Acad. Sci. USA, 92:2647-2651, 1995). However, nodules formed by plants from different groups are distinct in nodule organogenesis and structure. In most groups, nodule organogenesis involves the induction of cortical cell divisions. In legumes these divisions lead to the formation of a nodule primordium, while in non-legumes they lead to the formation of a so-called prenodule consisting of infected and uninfected cells. Nodule primordium formation does not involve prenodule cells, and the function of prenodules is not known. Here, we examine the differentiation of actinorhizal prenodule cells in comparison to nodule cells with regard to both symbionts. Our findings indicate that prenodules represent primitive symbiotic organs whose cell types display the same characteristics as their nodule counterparts. The results are discussed in the context of the evolution of root nodule symbioses.
近期的系统发育研究表明，所有能够与固氮细菌形成根瘤共生关系的植物都可追溯到一个共同祖先（D.E. 索尔蒂斯、P.S. 索尔蒂斯、D.R. 摩根、S.M. 斯文森、B.C. 穆林、J.M. 多德和P.G. 马丁，《美国国家科学院院刊》，92:2647 - 2651，1995年）。然而，不同植物类群形成的根瘤在根瘤器官发生和结构上存在差异。在大多数植物类群中，根瘤器官发生涉及皮层细胞分裂的诱导。在豆科植物中，这些分裂导致根瘤原基的形成，而在非豆科植物中，它们导致形成由受感染和未受感染细胞组成的所谓前根瘤。根瘤原基的形成不涉及前根瘤细胞，且前根瘤的功能尚不清楚。在此，我们比较了放线菌根瘤前根瘤细胞与根瘤细胞在两种共生体方面的分化情况。我们的研究结果表明，前根瘤代表原始的共生器官，其细胞类型与根瘤对应细胞具有相同的特征。我们将在根瘤共生进化的背景下讨论这些结果。
