Plants can enhance their defence against herbivorous insects by responding to insect egg depositions preceding larval feeding. The similarity of plant responses to insect eggs with those to phytopathogens gave rise to the hypothesis that egg‐associated microbes might act as elicitors. We tested this hypothesis by investigating first if elimination of microbes in the butterfly Pieris brassicae changes the responses of Brassica nigra and Arabidopsis thaliana to eggs and larvae of this insect species. An antibiotic treatment of butterflies mitigated the plant transcriptional response to the eggs and the egg‐mediated enhancement of the plant's defence against larvae. However, application of cultivated microbial isolates from the eggs onto Arabidopsis thaliana did not enhance the plant's anti‐herbivore defence. Instead, application of an egg‐associated glandular secretion, which is attaching the eggs to the leaves, elicited the enhancing effect on the plant's defence against larvae. However, this effect was only achieved when the secretion was applied in similar quantities as released by control butterflies, but not when applied in the reduced quantity as released by antibiotic‐treated butterflies. We conclude that glandular secretions rather than egg‐associated microbes act in a dose‐dependent manner as elicitor of the egg‐mediated enhancement of the plant's defence against insect larvae.

中文翻译：

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植物对昆虫卵的反应不是由卵相关微生物诱导的，而是由卵上附着的分泌物诱导的。

植物可以通过在喂食幼虫之前对卵的沉积作出反应，从而增强对草食性昆虫的防御能力。植物对昆虫卵的反应与对植物病原体的反应相似，因此提出了这样一个假说，即与卵有关的微生物可能是引发剂。我们首先研究了蝴蝶蝶粉中是否消除了微生物，从而改变了芸苔和拟南芥对这种虫卵和幼虫的反应，从而检验了这一假设。蝴蝶对蝴蝶的抗生素处理减轻了植物对卵的转录反应，并增强了卵介导的植物对幼虫的防御能力。然而，将培养的微生物分离物从卵上应用到拟南芥不能增强植物的抗草食动物防御能力。取而代之的是，将与卵相关的腺体分泌物附着在叶子上，从而增强了其对幼虫的防御能力。但是，只有当分泌物的添加量与对照蝴蝶释放的量相似时，才能达到这种效果，而当抗生素处理的蝴蝶释放的分泌物量减少时，则不能达到这种效果。我们得出的结论是，腺体分泌物而不是与卵相关的微生物以剂量依赖的方式引起卵对植物抵御昆虫幼虫的防御作用的增强。