Genome characteristics of facultatively symbiotic Frankia sp strains reflect host range and host plant biogeography
Genome characteristics of facultatively symbiotic Frankia sp strains reflect host range and host plant biogeography
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DOI：
10.1101/gr.5798407
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发表时间：
2007-01-01
期刊：
影响因子：
7
通讯作者：
Benson, David R.
中科院分区：
文献类型：
--
作者：
Normand, Philippe;Lapierre, Pascal;Benson, David R.
在植物中也形成互惠共生的土壤细菌遇到两个主要层次的选择。一个发生在适应和生存在土壤中，另一个发生在音乐会与宿主植物的物种形成和适应。Frankia属的放线菌是兼性共生体，它们在“辐射根”共生体中的多种全球分布的被子植物上形成固定N-2的根瘤。Frankia sp.菌株的三个密切相关的分支被确认;每个分支的成员感染来自八个被子植物科的植物子集。我们对来自三个菌株的基因组进行了测序;它们的大小从窄宿主范围菌株（Frankia sp.菌株HFPCcl 3）的5.43 Mbp到中等宿主范围菌株（Frankia alni菌株ACN 14 a）的7.50 Mbp到宽宿主范围菌株（Frankia sp.菌株EANlpec）的9.04 Mbp变化。这种大小差异是迄今为止报道的这种密切相关的土壤细菌的最大差异（16 S rRNA基因的97.8% - 98.9%同一性）。基因缺失、复制和获得的程度与共生体和宿主植物物种形成的地理历史相一致。寄主植物隔离有利于基因组收缩，而寄主植物多样化有利于基因组扩增。结果支持这样的想法，即主要基因组扩增以及减少可以发生在兼性共生土壤细菌，因为它们响应新的环境中的共生环境。
Soil bacteria that also form mutualistic symbioses in plants encounter two major levels of selection. One occurs during adaptation to and survival in soil, and the other occurs in concert with host plant speciation and adaptation. Actinobacteria from the genus Frankia are facultative symbionts that form N-2-fixing root nodules on diverse and globally distributed angiosperms in the "actinorhizal" symbioses. Three closely related clades of Frankia sp. strains are recognized; members of each clade infect a subset of plants from among eight angiosperm families. We sequenced the genomes from three strains; their sizes varied from 5.43 Mbp for a narrow host range strain (Frankia sp. strain HFPCcl3) to 7.50 Mbp for a medium host range strain (Frankia alni strain ACNl4a) to 9.04 Mbp for a broad host range strain (Frankia sp. strain EANlpec.) This size divergence is the largest yet reported for such closely related soil bacteria (97.8% - 98.9% identity of 16S rRNA genes). The extent of gene deletion, duplication, and acquisition is in concert with the biogeographic history of the symbioses and host plant speciation. Host plant isolation favored genome contraction, whereas host plant diversification favored genome expansion. The results support the idea that major genome expansions as well as reductions can occur in facultative symbiotic soil bacteria as they respond to new environments in the context of their symbioses.