Insect Symbiosis Research Group, Max Planck Institute for Chemical Ecology, Hans-Knöll-Straβe 8, 07745 Jena, Germany.
Department for Evolutionary Ecology, Institute of Organismic and Molecular Evolution, Johannes Gutenberg University, Johann-Joachim-Becher-Weg 13, 55128 Mainz, Germany.
Nat Commun. 2017 Apr 28;8:15172. doi: 10.1038/ncomms15172.
Pathogenic and mutualistic bacteria associated with eukaryotic hosts often lack distinctive genomic features, suggesting regular transitions between these lifestyles. Here we present evidence supporting a dynamic transition from plant pathogenicity to insect-defensive mutualism in symbiotic Burkholderia gladioli bacteria. In a group of herbivorous beetles, these symbionts protect the vulnerable egg stage against detrimental microbes. The production of a blend of antibiotics by B. gladioli, including toxoflavin, caryoynencin and two new antimicrobial compounds, the macrolide lagriene and the isothiocyanate sinapigladioside, likely mediate this defensive role. In addition to vertical transmission, these insect symbionts can be exchanged via the host plant and retain the ability to initiate systemic plant infection at the expense of the plant's fitness. Our findings provide a paradigm for the transition between pathogenic and mutualistic lifestyles and shed light on the evolution and chemical ecology of this defensive mutualism.
与真核宿主相关的病原和共生细菌通常缺乏独特的基因组特征，这表明它们在这些生活方式之间经常发生转变。在这里，我们提供了支持共生伯克霍尔德氏菌从植物致病性到昆虫防御性共生关系动态转变的证据。在一群草食性甲虫中，这些共生菌保护脆弱的卵期免受有害微生物的侵害。B. gladioli 产生的抗生素混合物，包括毒黄素、 Caryoynencin 和两种新的抗菌化合物，大环内酯 lagriene 和异硫氰酸酯 sinapigladioside，可能介导了这种防御作用。除了垂直传播，这些昆虫共生菌可以通过宿主植物进行交换，并保留在牺牲植物适应性的情况下引发系统性植物感染的能力。我们的发现为病原和共生生活方式之间的转变提供了范例，并揭示了这种防御共生关系的进化和化学生态学。
