Hou Wei-Guo, Lian Bin
Jiangsu Key laboratory for Biodiversity and Biotechnology, Nanjing, China.
Yi Chuan. 2007 Jan;29(1):118-26. doi: 10.1360/yc-007-0118.
Symbiotic nitrogen fixing bacteria-known as rhizobia-harbour a set of nodulation (nod) genes that control the synthesis of modified lipo-chitooligosaccharides, called Nod factors that are required for legume nodulation. The nodA gene, which is essential for symbiosis, is responsible for the attachment of the fatty acid group to the oligosaccharide backbone. The nodZ, nolL, and noeI genes are involved in specific modifications of Nod factors common to bradyrhizobia, i.e., the transfer of a fucosyl group on the Nod factor core, fucose acetylation and fucose methylation, respectively. The distribution of the nodZ, nolL, and noeI genes in the studied strains was found to correlate with the nodA tree topology. Moreover, the nodA, nodZ, and noeI phylogenies were largely congruent, but did not closely follow the taxonomy of the strains shown by the housekeeping 16S rRNA and dnaK genes. Additionally, the distribution of nodZ, noeI, and nolL genes suggested that their presence may be related to the requirements of their legume hosts. These data indicated that the spread and maintenance of nodulation genes within the Bradyrhizobium genus occurred through vertical transmission, although lateral gene transfer also played a significant role.
共生固氮细菌（称为根瘤菌）含有一组结瘤（nod）基因，这些基因控制修饰的脂壳寡糖的合成，这种脂壳寡糖被称为豆科植物结瘤所需的结瘤因子（Nod因子）。对共生至关重要的nodA基因负责将脂肪酸基团连接到寡糖主链上。nodZ、nolL和noeI基因分别参与慢生根瘤菌共有的Nod因子的特定修饰，即Nod因子核心上岩藻糖基的转移、岩藻糖乙酰化和岩藻糖甲基化。研究发现，nodZ、nolL和noeI基因在所研究菌株中的分布与nodA树形拓扑结构相关。此外，nodA、nodZ和noeI系统发育在很大程度上是一致的，但并不紧密遵循看家基因16S rRNA和dnaK基因所显示的菌株分类学。此外，nodZ、noeI和nolL基因的分布表明它们的存在可能与豆科植物宿主的需求有关。这些数据表明，慢生根瘤菌属内结瘤基因的传播和维持是通过垂直传递发生的，尽管横向基因转移也发挥了重要作用。
