Department of Environmental and Life Sciences, Toyohashi University of Technology, Toyohashi, Aichi, Japan.
Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of America.
PLoS One. 2019 May 2;14(5):e0216319. doi: 10.1371/journal.pone.0216319. eCollection 2019.
The Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Sternorrhyncha: Psylloidea: Liviidae) is an important pest of citrus species worldwide because it transmits Candidatus Liberibacter spp. (Alphaproteobacteria), the causative agents of an incurable citrus disease known as huanglongbing or greening disease. Diaphorina citri possesses a vertically-transmitted intracellular symbiont, Candidatus Profftella armatura (Betaproteobacteria), which produces diaphorin, a polyketide that is significantly toxic to mammalian cells. Diaphorin is an analog of pederin, a defensive polyketide in the body fluid of Paederus rove beetles (Coleoptera: Staphylinidae) that deters predators. In the present study, as a first step to assess the possibility that diaphorin is toxic to biological control agents, we assayed diaphorin activities against insects and fungi. The target cells and organisms were (a) the Sf9 cell line derived from the fall armyworm moth Spodoptera frugiperda (Lepidoptera: Noctuidae), (b) the pea aphid Acyrthosiphon pisum (Hemiptera: Sternorrhyncha: Aphidoidea: Aphididae), a phloem sap-sucking insect that is closely related to psyllids, (c) the Asian lady beetle Harmonia axyridis (Coleoptera: Coccinellidae), one of the major predators of D. citri, and (d) the budding yeast Saccharomyces cerevisiae (Ascomycota: Saccharomycetes) as a model of fungal pathogens. For a comparison, we also evaluated pederin activities. The results of our analyses revealed the following: (1) Diaphorin and pederin are significantly toxic to the tested insects and yeast; (2) Their toxicities vary widely among the target cells and organisms; (3) Diaphorin is generally less toxic than pederin; (4) The toxicities of diaphorin and pederin are considerably different in the Sf9 insect cell line and S. cerevisiae, but similar in A. pisum and H. axyridis; and (5) The amount of diaphorin contained in D. citri is toxic to all of the tested cells and organisms, suggesting that this polyketide is potentially harmful for biological control agents.
亚洲柑橘木虱 Diaphorina citri Kuwayama（半翅目：缨翅目：叶蝉科）是一种重要的柑橘属物种害虫，因为它传播候选利夫杆菌属（变形菌门：α 变形菌），这是一种无法治愈的柑橘疾病的病原体，被称为黄龙病或绿化病。亚洲柑橘木虱拥有一种垂直传播的细胞内共生体，候选普罗夫泰勒菌属（β 变形菌），它产生一种叫做二氢黄酮的聚酮化合物，对哺乳动物细胞有显著的毒性。二氢黄酮是一种与 pederin 相似的物质，pederin 是一种存在于拟步甲科（鞘翅目：隐翅虫科）步行虫体液中的防御性聚酮化合物，可以阻止捕食者。在本研究中，作为评估二氢黄酮对生物防治剂可能具有毒性的第一步，我们测定了二氢黄酮对昆虫和真菌的活性。靶细胞和生物包括：（a）来源于秋粘虫夜蛾 Spodoptera frugiperda（鳞翅目：夜蛾科）的 Sf9 细胞系，（b）豌豆蚜 Acyrthosiphon pisum（半翅目：缨翅目：蚜科），一种与木虱密切相关的吸食韧皮部汁液的昆虫，（c）亚洲瓢虫 Harmonia axyridis（鞘翅目：瓢虫科），一种柑橘木虱的主要捕食者，（d）作为真菌病原体模型的酿酒酵母 Saccharomyces cerevisiae（子囊菌门：酵母纲）。为了进行比较，我们还评估了 pederin 的活性。我们的分析结果表明：（1）二氢黄酮和 pederin 对测试的昆虫和酵母具有显著的毒性；（2）它们的毒性在靶细胞和生物之间差异很大；（3）二氢黄酮的毒性一般低于 pederin；（4）二氢黄酮和 pederin 在 Sf9 昆虫细胞系和 S. cerevisiae 中的毒性差异很大，但在 A. pisum 和 H. axyridis 中相似；（5）柑橘木虱中所含的二氢黄酮量对所有测试的细胞和生物均有毒性，表明这种聚酮化合物可能对生物防治剂有害。
