Department of Entomology and Nematology, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel.
Department of Entomology and Nematology, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel.
J Invertebr Pathol. 2019 Jan;160:43-53. doi: 10.1016/j.jip.2018.12.003. Epub 2018 Dec 4.
Insects show adaptive plasticity by ingesting plant secondary compounds, such as phenolic compounds, that are noxious to parasites. This work examined whether exposure to phenolic compounds affects the development of insect parasitic nematodes. As a model system for parasitic life cycle, we used Heterorhabditis bacteriophora (Rhabditida; Heterorhabditiade) grown with Photorhabdita luminescens supplemented with different concentrations of plant phenolic extracts (0, 600, 1200, 2400 ppm): a crude ethanol extract of lentisk (Pistacia lentiscus) or lentisk extract fractionated along a scale of hydrophobicity with hexane, chloroform and ethyl acetate; and flavonoids (myricetin, catechin), flavanol-glycoside (rutin) or phenolic acids (chlorogenic and gallic acids). Resilience of the nematode to phenolic compounds was stage-dependent, with younger growth stages exhibiting less resilience than older growth stages (i.e., eggs < young juveniles < young hermaphrodites < infective juveniles < mature hermaphrodites). At high concentrations, all of the phenolic compounds studied were lethal to eggs and young juveniles. The nematodes were able to survive in the presence of medium and low concentrations of all studied compounds, but very few of those treatments allowed for reproduction beyond the infective juvenile stage and, at low concentrations, the crude 70% ethanol extract, chloroform and hexane extracts, and myricetin were associated with some impaired reproduction. The ethyl-acetate fraction and gallic acid were extremely lethal to the young stages and allowed almost no development beyond the infective juvenile stage. We conclude that exposure of infective juveniles to phenolics before they infect insects and post-infection exposure of other nematode developmental stages may affect the initiation of the infection, suggesting that the chemistry of dietary phenolics may limit H. bacteriophora's infection of insects.
昆虫通过摄入对寄生虫有害的植物次生化合物，如酚类化合物，表现出适应性可塑性。本研究旨在探讨暴露于酚类化合物是否会影响昆虫寄生线虫的发育。作为寄生生命周期的模型系统，我们使用 Heterorhabditis bacteriophora（Rhabditida；Heterorhabditidae），该菌在添加不同浓度植物酚提取物（0、600、1200、2400ppm）的 Photorhabdita luminescens 中生长：松脂（Pistacia lentiscus）的粗乙醇提取物或按疏水性分级的松脂提取物，用正己烷、氯仿和乙酸乙酯；以及类黄酮（杨梅素、儿茶素）、黄烷醇糖苷（芦丁）或酚酸（绿原酸和没食子酸）。线虫对酚类化合物的弹性具有阶段性，幼龄生长阶段的弹性低于老龄生长阶段（即卵<幼龄幼虫<幼龄雌雄同体<感染性幼虫<成熟雌雄同体）。在高浓度下，所有研究的酚类化合物对卵和幼龄幼虫都是致命的。线虫能够在存在中低浓度所有研究化合物的情况下存活，但很少有处理允许繁殖超出感染性幼虫阶段，并且在低浓度下，粗 70%乙醇提取物、氯仿和正己烷提取物以及杨梅素与一些繁殖受损有关。乙酸乙酯馏分和没食子酸对幼龄阶段极为致命，几乎不允许发育超出感染性幼虫阶段。我们得出的结论是，在感染昆虫之前，感染性幼虫暴露于酚类化合物，以及感染后其他线虫发育阶段暴露于酚类化合物，可能会影响感染的开始，这表明饮食中酚类化合物的化学性质可能会限制 H. bacteriophora 对昆虫的感染。
