Nodulation of Sesbania species by Rhizobium (Agrobacterium) strain IRBG74 and other rhizobia
Nodulation of Sesbania species by Rhizobium (Agrobacterium) strain IRBG74 and other rhizobia
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DOI：
10.1111/j.1462-2920.2009.01975.x
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发表时间：
2009-10-01
影响因子：
5.1
通讯作者：
James, Euan K.
中科院分区：
文献类型：
--
作者：
Cummings, Stephen P.;Gyaneshwar, Prasad;James, Euan K.
通过16S rRNA、rpoB和fusA基因的序列分析，鉴定了从水生豆科植物大麻田菁根瘤中分离到的一株细菌（IRBG74）为植物病原菌放射根瘤菌（Rhizobium radiobacter）的近亲。然而，DNA：与R. radiobacter、R. rubi、R. vitis和R. huautlense的DNA杂交相似性分别为44%、5%、8%和8%，表明IRBG74可能是一个新种。此外，它不含vir基因，缺乏肿瘤形成能力，但含有与其他Sesbania共生体相似的nifH和nodA基因的同质粒。事实上，IRBG74有效地结瘤了S. cannabina和其他7种与具有相似nodA基因的Ensifer (Sinorhizobium)/Rhizobium菌株结瘤的Sesbania spp.，但对与Azorhizobium或Mesorhizobium结瘤的物种无效。光镜和电镜观察结果显示，水淹条件下，IRBG74通过侧根连接侵染田葵，而非水淹条件下，IRBG74通过根毛侵染田葵。因此，IRBG74是第一个从根瘤菌（农杆菌）分支中确认的豆科结瘤共生体。与各种田菁共生菌的交叉接种研究表明，大麻大麻可与根瘤菌属和Ensifer属菌株形成完全有效的共生关系，与偶氮根瘤菌属菌株只能形成无效的共生关系，与中根根瘤菌（Mesorhizobium huakii）或无效的共生关系（Mesorhizobium plurifarium）。这些资料在田菁及其共生体的分子系统发育方面进行了讨论。
P>Concatenated sequence analysis with 16S rRNA, rpoB and fusA genes identified a bacterial strain (IRBG74) isolated from root nodules of the aquatic legume Sesbania cannabina as a close relative of the plant pathogen Rhizobium radiobacter (syn. Agrobacterium tumefaciens). However, DNA:DNA hybridization with R. radiobacter, R. rubi, R. vitis and R. huautlense gave only 44%, 5%, 8% and 8% similarity respectively, suggesting that IRBG74 is potentially a new species. Additionally, it contained no vir genes and lacked tumour-forming ability, but harboured a sym-plasmid containing nifH and nodA genes similar to those in other Sesbania symbionts. Indeed, IRBG74 effectively nodulated S. cannabina and seven other Sesbania spp. that nodulate with Ensifer (Sinorhizobium)/Rhizobium strains with similar nodA genes to IRBG74, but not species that nodulate with Azorhizobium or Mesorhizobium. Light and electron microscopy revealed that IRBG74 infected Sesbania spp. via lateral root junctions under flooded conditions, but via root hairs under non-flooded conditions. Thus, IRBG74 is the first confirmed legume-nodulating symbiont from the Rhizobium (Agrobacterium) clade. Cross-inoculation studies with various Sesbania symbionts showed that S. cannabina could form fully effective symbioses with strains in the genera Rhizobium and Ensifer, only ineffective ones with Azorhizobium strains, and either partially effective (Mesorhizobium huakii) or ineffective (Mesorhizobium plurifarium) symbioses with Mesorhizobium. These data are discussed in terms of the molecular phylogeny of Sesbania and its symbionts.