Laboratory of Microbiology, Department of Biochemistry and Microbiology, Ghent University, Ghent, Belgium.
LIPME, Université de Toulouse, INRAE, CNRS, Castanet-Tolosan, France.
Environ Microbiol. 2023 Feb;25(2):454-472. doi: 10.1111/1462-2920.16292. Epub 2022 Dec 9.
The symbioses between plants of the Rubiaceae and Primulaceae families with Burkholderia bacteria represent unique and intimate plant-bacterial relationships. Many of these interactions have been identified through PCR-dependent typing methods, but there is little information available about their functional and ecological roles. We assembled 17 new endophyte genomes representing endophytes from 13 plant species, including those of two previously unknown associations. Genomes of leaf endophytes belonging to Burkholderia s.l. show extensive signs of genome reduction, albeit to varying degrees. Except for one endophyte, none of the bacterial symbionts could be isolated on standard microbiological media. Despite their taxonomic diversity, all endophyte genomes contained gene clusters linked to the production of specialized metabolites, including genes linked to cyclitol sugar analog metabolism and in one instance non-ribosomal peptide synthesis. These genes and gene clusters are unique within Burkholderia s.l. and are likely horizontally acquired. We propose that the acquisition of secondary metabolite gene clusters through horizontal gene transfer is a prerequisite for the evolution of a stable association between these endophytes and their hosts.
豆科和报春花科植物与伯克霍尔德氏菌之间的共生关系代表了独特而密切的植物-细菌关系。许多这些相互作用已经通过依赖 PCR 的分型方法来识别，但关于它们的功能和生态作用的信息却很少。我们组装了 17 个新的内生菌基因组，代表了来自 13 种植物的内生菌，其中包括两种以前未知的共生关系。属于伯克霍尔德氏菌的叶片内生菌的基因组显示出广泛的基因组缩小迹象，尽管程度不同。除了一个内生菌之外，没有一种细菌共生体可以在标准微生物培养基上分离出来。尽管它们具有丰富的分类多样性，但所有内生菌基因组都包含与特殊代谢产物产生相关的基因簇，包括与环醇糖类似物代谢相关的基因，以及在一个实例中非核糖体肽合成相关的基因。这些基因和基因簇在伯克霍尔德氏菌中是独特的，并且可能是水平获得的。我们提出，通过水平基因转移获得次生代谢物基因簇是这些内生菌与其宿主之间稳定共生关系进化的前提。
