Antimicrobial and Insecticidal: Cyclic Lipopeptides and Hydrogen Cyanide Produced by Plant-Beneficial Pseudomonas Strains CHA0, CMR12a, and PCL1391 Contribute to Insect Killing.
Antimicrobial and Insecticidal: Cyclic Lipopeptides and Hydrogen Cyanide Produced by Plant-Beneficial Pseudomonas Strains CHA0, CMR12a, and PCL1391 Contribute to Insect Killing.
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DOI：
10.3389/fmicb.2017.00100
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发表时间：
2017
影响因子：
5.2
通讯作者：
Maurhofer M
中科院分区：
文献类型：
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作者：
Flury P;Vesga P;Péchy-Tarr M;Aellen N;Dennert F;Hofer N;Kupferschmied KP;Kupferschmied P;Metla Z;Ma Z;Siegfried S;de Weert S;Bloemberg G;Höfte M;Keel CJ;Maurhofer M
特定的植物有益荧光假单胞菌群不仅是提供植物疾病抑制的根定殖菌，而且能够感染和杀死昆虫幼虫。细菌如何设法感染这个替代宿主，克服其免疫系统，并最终杀死昆虫的机制在很大程度上仍然未知。然而，对迄今为止发现的少数毒力因子的调查表明，杀虫活性具有高度多因素的性质。由荧光假单胞菌产生的抗菌化合物是对抗多种生物如真菌、卵菌、线虫和原生动物的有效武器。在这里，我们研究了这些化合物是否也有助于杀虫活性。我们测试了高杀虫性菌株假单胞菌protegens CHA0、绿单胞菌PCL1391和假单胞菌sp. CMR12a的突变体对鳞翅目昆虫幼虫的注射和口服活性，这些突变体对单个或多种抗菌化合物都有缺陷。此外，我们还首次研究了这些抗菌化合物的生物合成基因在昆虫中的表达。我们的调查发现，氰化氢和不同类型的环脂肽对杀虫活性有贡献。氰化氢是直接注射到血淋巴的CHA0和PCL1391完全毒力所必需的。由CHA0和CMR12a产生的环脂肽orfamide在口腔感染中起主要作用。在注射和饲养实验中，CMR12a和PCL1391突变体分别破坏了环脂肽sessilin和clp1391的产生，显示出毒性降低。虽然缺乏一种或几种其他抗菌化合物的突变体，即2,4-二乙酰间苯三酚、吩嗪、吡咯硝丁或pyoluteorin的毒力没有降低，但这些代谢物可能仍然在昆虫背景中发挥作用，因为所研究的菌株CHA0抗菌化合物的所有生物合成基因都在昆虫感染期间的某个时刻表达。总之，本研究发现了影响杀虫活性的新因素，并将荧光假单胞菌产生的抗菌化合物的多种功能从植物环境扩展到昆虫宿主。
Particular groups of plant-beneficial fluorescent pseudomonads are not only root colonizers that provide plant disease suppression, but in addition are able to infect and kill insect larvae. The mechanisms by which the bacteria manage to infest this alternative host, to overcome its immune system, and to ultimately kill the insect are still largely unknown. However, the investigation of the few virulence factors discovered so far, points to a highly multifactorial nature of insecticidal activity. Antimicrobial compounds produced by fluorescent pseudomonads are effective weapons against a vast diversity of organisms such as fungi, oomycetes, nematodes, and protozoa. Here, we investigated whether these compounds also contribute to insecticidal activity. We tested mutants of the highly insecticidal strains Pseudomonas protegens CHA0, Pseudomonas chlororaphis PCL1391, and Pseudomonas sp. CMR12a, defective for individual or multiple antimicrobial compounds, for injectable and oral activity against lepidopteran insect larvae. Moreover, we studied expression of biosynthesis genes for these antimicrobial compounds for the first time in insects. Our survey revealed that hydrogen cyanide and different types of cyclic lipopeptides contribute to insecticidal activity. Hydrogen cyanide was essential to full virulence of CHA0 and PCL1391 directly injected into the hemolymph. The cyclic lipopeptide orfamide produced by CHA0 and CMR12a was mainly important in oral infections. Mutants of CMR12a and PCL1391 impaired in the production of the cyclic lipopeptides sessilin and clp1391, respectively, showed reduced virulence in injection and feeding experiments. Although virulence of mutants lacking one or several of the other antimicrobial compounds, i.e., 2,4-diacetylphloroglucinol, phenazines, pyrrolnitrin, or pyoluteorin, was not reduced, these metabolites might still play a role in an insect background since all investigated biosynthetic genes for antimicrobial compounds of strain CHA0 were expressed at some point during insect infection. In summary, our study identified new factors contributing to insecticidal activity and extends the diverse functions of antimicrobial compounds produced by fluorescent pseudomonads from the plant environment to the insect host.