Stepkowski Tomasz, Hughes Colin E, Law Ian J, Markiewicz Łukasz, Gurda Dorota, Chlebicka Agnieszka, Moulin Lionel
Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12/14, 61 704 Poznań, Poland.
Appl Environ Microbiol. 2007 May;73(10):3254-64. doi: 10.1128/AEM.02125-06. Epub 2007 Mar 30.
Bradyrhizobium strains isolated in Europe from Genisteae and serradella legumes form a distinct lineage, designated clade II, on nodulation gene trees. Clade II bradyrhizobia appear to prevail also in the soils of Western Australia and South Africa following probably accidental introduction with seeds of their lupine and serradella hosts. Given this potential for dispersal, we investigated Bradyrhizobium isolates originating from a range of native New World lupines, based on phylogenetic analyses of nodulation (nodA, nodZ, noeI) and housekeeping (atpD, dnaK, glnII, recA) genes. The housekeeping gene trees revealed considerable diversity among lupine bradyrhizobia, with most isolates placed in the Bradyrhizobium japonicum lineage, while some European strains were closely related to Bradyrhizobium canariense. The nodA gene tree resolved seven strongly supported groups (clades I to VII) that correlated with strain geographical origins and to some extent with major Lupinus clades. All European strains were placed in clade II, whereas only a minority of New World strains was placed in this clade. This work, as well as our previous studies, suggests that clade II diversified predominately in the Old World, possibly in the Mediterranean. Most New World isolates formed subclade III.2, nested in a large "pantropical" clade III, which appears to be New World in origin, although it also includes strains originating from nonlupine legumes. Trees generated using nodZ and noeI gene sequences accorded well with the nodA tree, but evidence is presented that the noeI gene may not be required for nodulation of lupine and that loss of this gene is occurring.
在欧洲从染料木属和草木犀属豆科植物中分离出的慢生根瘤菌菌株，在结瘤基因树上形成了一个独特的谱系，称为分支II。分支II慢生根瘤菌似乎也在西澳大利亚和南非的土壤中占主导地位，这可能是随着其羽扇豆和草木犀宿主的种子意外引入的。鉴于这种传播潜力，我们基于对结瘤基因（nodA、nodZ、noeI）和管家基因（atpD、dnaK、glnII、recA）的系统发育分析，研究了源自新大陆一系列本地羽扇豆的慢生根瘤菌分离株。管家基因树揭示了羽扇豆慢生根瘤菌之间存在相当大的多样性，大多数分离株属于日本慢生根瘤菌谱系，而一些欧洲菌株与加那利慢生根瘤菌密切相关。nodA基因树解析出七个得到有力支持的组（分支I至VII），这些组与菌株的地理起源相关，并在一定程度上与主要的羽扇豆分支相关。所有欧洲菌株都属于分支II，而只有少数新大陆菌株属于该分支。这项工作以及我们之前的研究表明，分支II主要在旧世界多样化，可能在地中海地区。大多数新大陆分离株形成了亚分支III.2，嵌套在一个大型的“泛热带”分支III中，该分支似乎起源于新大陆，尽管它也包括源自非羽扇豆豆科植物的菌株。使用nodZ和noeI基因序列生成的树与nodA树吻合良好，但有证据表明，noeI基因可能不是羽扇豆结瘤所必需的，并且该基因正在发生丢失。
