Plant phenolics are generally thought to play significant roles in plant defense against herbivores and pathogens. Many plant taxa, including Solanaceae, are rich in phenolic compounds and some insect herbivores have been shown to acquire phenolics from their hosts to use them as protection against their natural enemies. Here, we demonstrate that larvae of an insect specialist on Solanaceae, the tobacco hornworm, Manduca sexta L. (Lepidoptera: Sphingidae), acquire the plant phenolic chlorogenic acid (CA), and other caffeic acid derivatives as they feed on one of their hosts, Nicotiana attenuata L. (Solanaceae), and on artificial diet supplemented with CA. We test the hypothesis that larvae fed on CA‐supplemented diet would have better resistance against bacterial infection than larvae fed on a standard CA‐free diet by injecting bacteria into the hemocoel of fourth instars. Larvae fed CA‐supplemented diet show significantly higher survival of infection with Enterococcus faecalis (Andrewes & Horder) Schleifer & Kilpper‐Bälz, but not of infection with the more virulent Pseudomonas aeruginosa (Schroeter) Migula. Larvae fed on CA‐supplemented diet possess a constitutively higher number of circulating hemocytes than larvae fed on the standard diet, but we found no other evidence of increased immune system activity, nor were larvae fed on CA‐supplemented diet better able to suppress bacterial proliferation early in the infection. Thus, our data suggest an additional defensive function of CA to the direct toxic inhibition of pathogen proliferation in the gut.

中文翻译：

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膳食植物酚可提高六毛虫中细菌感染的存活率

植物酚类物质通常被认为在植物防御食草动物和病原体方面发挥重要作用。许多植物类群，包括茄科，富含酚类化合物，一些昆虫食草动物已被证明从宿主那里获取酚类物质，以利用它们来抵御天敌。在这里，我们证明了茄科昆虫专家的幼虫，烟草角虫 Manduca sexta L.（鳞翅目：鞘翅目），当它们以宿主之一为食时，会获得植物酚绿原酸 (CA) 和其他咖啡酸衍生物, Nicotiana attenuata L. (茄科), 并在人工饮食中添加 CA。我们通过将细菌注射到四龄的血腔中来检验以下假设，即以 CA 补充饮食喂养的幼虫比以标准无 CA 饮食喂养的幼虫对细菌感染具有更好的抵抗力。用 CA 补充饮食喂养的幼虫对粪肠球菌 (Andrewes & Horder) Schleifer & Kilpper-Bälz 的感染存活率显着提高，但对毒性更强的铜绿假单胞菌 (Schroeter) Migula 感染的存活率则不然。以 CA 补充饮食喂养的幼虫比标准饮食喂养的幼虫具有更多数量的循环血细胞，但我们没有发现免疫系统活性增加的其他证据，也没有发现 CA 补充饮食喂养的幼虫能够更好地抑制细菌增殖感染初期。因此，