INTRODUCTION The oxylipin methyl jasmonate (MeJA) is a plant hormone active in response signalling and defence against herbivores. Although MeJA is applied experimentally to mimic herbivory and induce plant defences, its downstream effects on the plant metabolome are largely uncharacterized, especially in the context of primary growth and tissue-specificity of the response. OBJECTIVES We investigated the effects of MeJA-simulated and real caterpillar herbivory on the foliar metabolome of the wild plant Brassica nigra and monitored the herbivore-induced responses in relation to leaf ontogeny. METHODS As single or multiple herbivory treatments, MeJA- and mock-sprayed plants were consecutively exposed to caterpillars or left untreated. Gas chromatography (GC) and liquid chromatography (LC) time-of-flight mass-spectrometry (TOF-MS) were combined to analyse foliar compounds, including central primary and specialized defensive plant metabolites. RESULTS Plant responses were stronger in young leaves, which simultaneously induced higher chlorophyll levels. Both MeJA and caterpillar herbivory induced similar, but not identical, accumulation of tricarboxylic acids (TCAs), glucosinolates (GSLs) and phenylpropanoids (PPs), but only caterpillar feeding led to depletion of amino acids. MeJA followed by caterpillars caused higher induction of defence compounds, including a three-fold increase in the major defence compound allyl-GSL (sinigrin). When feeding on MeJA-treated plants, caterpillars gained less weight indicative of the reduced host-plant quality and enhanced resistance. CONCLUSIONS The metabolomics approach showed that plant responses induced by herbivory extend beyond the regulation of defence metabolism and are tightly modulated throughout leaf development. This leads to a new understanding of the plant metabolic potential that can be exploited for future plant protection strategies.

中文翻译：

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黑芥菜（Brassica nigra）中的真实和模拟食草诱导的叶片代谢特征。

简介茉莉酮酸甲酯（MeJA）是一种植物激素，在应答信号和防御食草动物中具有活性。尽管MeJA已通过实验方法应用于模仿食草动物并诱导植物防御，但其对植物代谢组的下游影响在很大程度上尚未被表征，特别是在主要生长和响应的组织特异性的情况下。目的我们研究了MeJA模拟的和真实的毛虫食草对野生植物芸苔的叶片代谢组的影响，并监测了食草动物诱导的与叶片个体发育相关的反应。方法作为一次或多次食草处理，将MeJA和模拟喷洒的植物连续暴露于毛毛虫或未经处理。气相色谱（GC）和液相色谱（LC）飞行时间质谱（TOF-MS）结合起来分析了叶状化合物，包括主要的初级防御植物代谢产物和专门的防御性植物代谢产物。结果植物嫩叶中的反应较强，同时诱导较高的叶绿素水平。MeJA和毛毛虫草食动物均诱导相似但不完全的三羧酸（TCA），芥子油苷（GSLs）和苯丙烷类（PPs）积累，但是只有毛毛虫饲喂会导致氨基酸消耗。MeJA和随后的毛毛虫引起较高的防御化合物诱导作用，包括主要防御化合物烯丙基-GSL（sinigrin）增加了三倍。以MeJA处理的植物为食时，毛毛虫的体重减轻，表明寄主植物的品质下降和抗性增强。结论代谢组学方法表明，由草食动物引起的植物反应超出了防御代谢的调控范围，并在整个叶片发育过程中受到严格调控。这使人们对植物的新陈代谢潜力有了新的认识，可以将其用于未来的植物保护策略。