印度的一种入侵性含羞草不采用其本地亲缘植物的共生体。
An invasive Mimosa in India does not adopt the symbionts of its native relatives.
机构信息
BNF and Stress Biology Lab., Department of Botany, J.N. Vyas University, Jodhpur-342001, India.
出版信息
Ann Bot. 2013 Jul;112(1):179-96. doi: 10.1093/aob/mct112. Epub 2013 May 26.
BACKGROUND AND AIMS
The large monophyletic genus Mimosa comprises approx. 500 species, most of which are native to the New World, with Central Brazil being the main centre of radiation. All Brazilian Mimosa spp. so far examined are nodulated by rhizobia in the betaproteobacterial genus Burkholderia. Approximately 10 Mya, transoceanic dispersal resulted in the Indian subcontinent hosting up to six endemic Mimosa spp. The nodulation ability and rhizobial symbionts of two of these, M. hamata and M. himalayana, both from north-west India, are here examined, and compared with those of M. pudica, an invasive species.
METHODS
Nodules were collected from several locations, and examined by light and electron microscopy. Rhizobia isolated from them were characterized in terms of their abilities to nodulate the three Mimosa hosts. The molecular phylogenetic relationships of the rhizobia were determined by analysis of 16S rRNA, nifH and nodA gene sequences.
KEY RESULTS
Both native Indian Mimosa spp. nodulated effectively in their respective rhizosphere soils. Based on 16S rRNA, nifH and nodA sequences, their symbionts were identified as belonging to the alphaproteobacterial genus Ensifer, and were closest to the 'Old World' Ensifer saheli, E. kostiensis and E. arboris. In contrast, the invasive M. pudica was predominantly nodulated by Betaproteobacteria in the genera Cupriavidus and Burkholderia. All rhizobial strains tested effectively nodulated their original hosts, but the symbionts of the native species could not nodulate M. pudica.
CONCLUSIONS
The native Mimosa spp. in India are not nodulated by the Burkholderia symbionts of their South American relatives, but by a unique group of alpha-rhizobial microsymbionts that are closely related to the 'local' Old World Ensifer symbionts of other mimosoid legumes in north-west India. They appear not to share symbionts with the invasive M. pudica, symbionts of which are mostly beta-rhizobial.
背景与目的
含羞草属是一个大型的单系属，包含约 500 种植物，其中大多数原产于新大陆，巴西中部是辐射的主要中心。迄今为止，所有在巴西检查的含羞草属植物都被β变形菌属的根瘤菌结瘤。大约在 1000 万年前，跨洋传播导致印度次大陆拥有多达六种特有含羞草属植物。本文研究了来自印度西北部的两种特有含羞草，即含羞草（Mimosa hamata）和喜马拉雅含羞草（M. himalayana）的结瘤能力及其根瘤菌共生体，并与入侵种含羞草（M. pudica）进行了比较。
方法
从多个地点收集根瘤，并用光学显微镜和电子显微镜检查。从它们中分离出的根瘤菌，根据它们对三种含羞草宿主的结瘤能力进行了特征描述。通过分析 16S rRNA、nifH 和 nodA 基因序列，确定了根瘤菌的分子系统发育关系。
主要结果
两种本土印度含羞草属植物在其各自的根际土壤中有效结瘤。根据 16S rRNA、nifH 和 nodA 序列，它们的共生体被鉴定为属于α变形菌属的根瘤菌，与“旧世界”的根瘤菌 Ensifer saheli、E. kostiensis 和 E. arboris 最为接近。相比之下，入侵种含羞草主要由β变形菌属的 Cupriavidus 和 Burkholderia 属的根瘤菌结瘤。所有测试的根瘤菌菌株都有效地结瘤了它们的原始宿主，但这些本土物种的共生体不能结瘤含羞草。
结论
印度本土的含羞草属植物不是由其南美的亲缘关系的 Burkholderia 共生体结瘤，而是由一组与印度西北部其他豆科含羞草属植物的“本地”旧世界 Ensifer 共生体密切相关的独特的α根瘤菌共生体结瘤。它们似乎与入侵种含羞草不共享共生体，而含羞草的共生体主要是β根瘤菌。
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