Ultrasensitive detection by maxillary palp neurons allows non-host recognition without consumption of harmful allelochemicals
Ultrasensitive detection by maxillary palp neurons allows non-host recognition without consumption of harmful allelochemicals
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DOI：
10.1016/j.jinsphys.2021.104263
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发表时间：
2021-06-03
影响因子：
2.2
通讯作者：
Sato，Ryoichi
中科院分区：
文献类型：
--
作者：
Shii，Fumika;Mang，Dingze;Sato，Ryoichi
大多数鳞翅目昆虫幼虫表现出逐步取食行为，例如使用上颌须触诊（MP），然后进行测试咬和持续咬。然而，触诊的目的尚不清楚。特别是，人们对 MP 中的神经元及其识别不需要的植物的模式一无所知，尽管此类神经元已被认为存在。在这项研究中，我们使用窄食性昆虫家蚕的幼虫来比较触诊和测试咬合在选择摄食行为中的作用。当幼虫给予非寄主植物叶子时，它们没有发起测试咬，这表明非寄主植物叶子是通过触诊而不是咬来识别的，并且这种行为导致缺乏持续的咬，因为叶子被判断为不适合食用。不可食用叶子的表面提取物显着抑制了桑叶（B. 的寄主植物）的咬食试验。 mori，表明不可食用叶子的叶表面上的次生代谢物起到测试咬合抑制剂的作用，即使当其他条件适合测试咬合时也是如此。在樱桃（Cerasus spiosa）不可食用的叶子中发现的化感化学香豆素，显着抑制了对桑叶的咬测试，这表明香豆素可能是对樱桃叶食用的一种威慑。使用尖端记录的电生理学方法和叶表面提取物作为测试材料，在MP中鉴定了叶表面化合物反应神经元。此外，还鉴定出了几个对阿摩尔范围内的香豆素有反应的神经元，这表明幼虫利用 MP 中的超敏感神经元来识别不可食用的叶子。在HEK293T细胞异源表达系统中，B．先前发现在 MP 中表达并在阿托摩尔范围内对香豆素有反应的兴奋受体 BmGr53 和 BmGr19 对 C 的叶表面提取物有反应。 spiosa，表明这些受体可能存在于 MP 的非食用叶子识别神经元上。这些发现表明，MP 中超敏感的植物次生代谢物识别神经元允许通过触诊识别非宿主植物，而不会冒因摄入有害化感物质而造成损害的风险。
Most lepidopteran insect larvae exhibit stepwise feeding behaviors, such as palpation using the maxillary palps (MPs) followed by test biting and persistent biting. However, the purpose of palpation has been unclear. In particular, nothing is known about the neurons in the MP and their mode of recognition of undesired plants, although such neurons have been suggested to exist. In this study, we used larvae of the stenophagous insectBombyx moriand compared the roles of palpation and test biting in the selection of feeding behavior. When the larvae were given non-host plant leaves, they did not initiate test biting, indicating that non-host plant leaves were recognized via palpation without biting, and that this behavior resulted in a lack of persistent biting, as the leaves were judged non-suitable for consumption. Surface extracts of inedible leaves significantly suppressed test biting of mulberry leaves, a host plant ofB. mori, suggesting that secondary metabolites on the leaf surface of inedible leaves function as test biting suppressors, even when another conditions are suitable for test biting. The allelochemical coumarin, which is found in the inedible leaves of cherry,Cerasus speciosa, significantly suppressed test biting of mulberry leaves, suggesting that coumarin is a possible deterrent to the eating of cherry leaves. Using the electrophysiological method of tip recording and a leaf-surface extract as the test material, leaf-surface compound-responsive neurons were identified in the MP. In addition, several neurons that respond to coumarin in the attomolar range were identified, suggesting that the larvae use ultrasensitive neurons in the MP to recognize inedible leaves. In the HEK293T cell heterologous expression system, theB. morigustatory receptors BmGr53 and BmGr19, which were previously found to be expressed in the MP and to respond to coumarin in the attomolar range, responded to a leaf-surface extract ofC. speciosa, suggesting that these receptors may be present on the inedible-leaf-recognizing neurons of the MP. These findings suggest that ultrasensitive plant secondary metabolite-recognizing neurons in the MP allow for the recognition of non-host plants via palpation without risking damage caused by ingesting harmful allelochemicals.