Key Laboratory of Resource Biology and Biotechnology in Western China, Taibai North Rd. 229, Xi'an City, Shaanxi Province, China; Department of Life Science, Northwest University, Taibai North Rd. 229, Xi'an City, Shaanxi Province, China.
Key Laboratory of Resource Biology and Biotechnology in Western China, Taibai North Rd. 229, Xi'an City, Shaanxi Province, China; Department of Life Science, Northwest University, Taibai North Rd. 229, Xi'an City, Shaanxi Province, China.
Syst Appl Microbiol. 2021 Jul;44(4):126224. doi: 10.1016/j.syapm.2021.126224. Epub 2021 Jun 10.
To investigate the diversity and distribution of rhizobia associated with Sophora davidii in habitats with different light and soil conditions at the Loess Plateau, we isolated rhizobia from root nodules of this plant grown at 14 sites at forest edge or understory in Shaanxi Province. Based on PCR-RFLP and phylogenies of 16S rRNA gene, housekeeping genes (atpD, dnaK, recA), and symbiosis genes (nodC and nifH), a total of 271 isolates were identified as 16 Mesorhizobium genospecies, belonging to four nodC lineages, and three nifH lineages. The dominance of M. waimense in the forest edge and of M. amorphae/Mesorhizobium sp. X in the understory habitat evidenced the illumination as a possible factor to affect the diversity and biogeographic patterns of rhizobia. However, the results of Canonical Correlation Analysis (CCA) among the environmental factors and distribution of rhizobial genospecies illustrated that soil pH and contents of total phosphorus, total potassium and total organic carbon were the main determinants for the community structure of S. davidii rhizobia, while the illumination conditions and available P presented similar and minor effects. In addition, high similarity of nodC and nifH genes between Mesorhizobium robiniae and some S. davidii rhizobia under the forest of Robinia pseudoacacia might be evidence for symbiotic gene lateral transfer. These findings firstly brought an insight into the diversity and distribution of rhizobia associated with S. davidii, and revealed illumination conditions a possible factor with impacts less than the soil traits to drive the symbiosis association between rhizobia and their host legumes.
为了调查在黄土高原不同光照和土壤条件下与苦参共生的根瘤菌的多样性和分布，我们从陕西省 14 个森林边缘或林下种植的苦参根瘤中分离出根瘤菌。基于 PCR-RFLP 和 16S rRNA 基因、看家基因（atpD、dnaK、recA）和共生基因（nodC 和 nifH）的系统发育分析，共鉴定出 271 株菌为 16 个中慢生根瘤菌属种，属于四个 nodC 谱系和三个 nifH 谱系。在森林边缘以 M. waimense 为主，在林下以 M. amorphae/Mesorhizobium sp. X 为主，这表明光照可能是影响根瘤菌多样性和生物地理分布模式的一个因素。然而，CCA 分析结果表明，环境因素与根瘤菌种群分布之间的关系表明，土壤 pH 值以及总磷、总钾和总有机碳的含量是决定苦参根瘤菌群落结构的主要决定因素，而光照条件和有效磷则具有相似但较小的影响。此外，在刺槐林中，中慢生根瘤菌属 Robinia pseudoacacia 和一些苦参根瘤菌的 nodC 和 nifH 基因高度相似，这可能是共生基因横向转移的证据。这些发现首次深入了解了与苦参共生的根瘤菌的多样性和分布，并揭示了光照条件可能是一个比土壤特性影响较小的因素，驱动根瘤菌与其宿主豆科植物之间的共生关系。
