The study challenges the general belief that plants are highly sensitive to oral cues of herbivores and reveals the role of the damage level on the magnitude of defense induction. Many leaf-feeding caterpillars share similar feeding behaviors involving repeated removal of previously wounded leaf tissue (semicircle feeding pattern). We hypothesized that this behavior is a strategy to attenuate plant-induced defenses by removing both the oral cues and tissues that detect it. Using tobacco (Nicotiana tabacum) and the tobacco hornworm (Manduca sexta), we found that tobacco increased defensive responses during herbivory compared to mechanical wounding at moderate damage levels (30%). However, tobacco did not differentiate between mechanical wounding and herbivory when the level of leaf tissue loss was either small (4%) or severe (100%, whole leaf removal). Higher amounts of oral cues did not induce higher defenses when damage was small. Severe damage led to the highest level of systemic defense proteins compared to other levels of leaf tissue loss with or without oral cues. In conclusion, we did not find clear evidence that semicircle feeding behavior compromises plant defense induction. In addition, the level of leaf tissue loss and oral cues interact to determine the level of induced defensive responses in tobacco. Although oral cues play an important role in inducing defensive proteins, the level of induction depends more on the level of leaf tissue loss in tobacco.

中文翻译：

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口头提示是不够的：毛虫喂养后烟草中防御性蛋白的诱导

该研究挑战了植物对食草动物的口腔信号高度敏感的普遍看法，并揭示了损伤水平对防御诱导程度的作用。许多以叶片为食的毛毛虫具有相似的进食行为，包括反复去除先前受伤的叶片组织（半圆形进食模式）。我们假设这种行为是一种通过去除检测到它的口腔线索和组织来减弱植物诱导的防御的策略。使用烟草 (Nicotiana tabacum) 和烟草天蛾 (Manduca sexta)，我们发现与中等损伤水平 (30%) 的机械伤害相比，烟草在食草期间增加了防御反应。然而，当叶片组织损失程度很小（4%）或严重（100%，全叶去除）。当伤害较小时，较高数量的口头暗示不会引起较高的防御。与其他水平的叶片组织损失相比，无论是否有口腔提示，严重损伤导致系统防御蛋白水平最高。总之，我们没有找到明确的证据表明半圆形摄食行为会损害植物防御诱导。此外，叶片组织损失的水平和口腔信号相互作用决定了烟草中诱导防御反应的水平。尽管口腔信号在诱导防御性蛋白方面发挥重要作用，但诱导水平更多地取决于烟草中叶片组织损失的水平。与其他水平的叶片组织损失相比，无论是否有口腔提示，严重损伤导致系统防御蛋白水平最高。总之，我们没有找到明确的证据表明半圆形摄食行为会损害植物防御诱导。此外，叶片组织损失的水平和口腔信号相互作用决定了烟草中诱导防御反应的水平。尽管口腔信号在诱导防御性蛋白方面发挥重要作用，但诱导水平更多地取决于烟草中叶片组织损失的水平。与其他水平的叶片组织损失相比，无论是否有口腔提示，严重损伤导致系统防御蛋白水平最高。总之，我们没有找到明确的证据表明半圆形摄食行为会损害植物防御诱导。此外，叶片组织损失的水平和口腔信号相互作用决定了烟草中诱导防御反应的水平。尽管口腔信号在诱导防御性蛋白方面发挥重要作用，但诱导水平更多地取决于烟草中叶片组织损失的水平。