Molecular adaptation of Chrysochus leaf beetles to toxic compounds in their food plants
Molecular adaptation of Chrysochus leaf beetles to toxic compounds in their food plants
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DOI：
10.1093/molbev/msg240
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发表时间：
2004-02-01
影响因子：
10.7
通讯作者：
Dobler, S
中科院分区：
文献类型：
--
作者：
Labeyrie, E;Dobler, S
以有毒植物为食的食草动物必须克服植物的防御，有时甚至可以从中受益。当前的挑战是了解食草动物如何进化必要的生理适应以及涉及哪些分子水平的变化。在此背景下，我们研究了叶甲属Chrysochus（鞘翅目，姬小蜂科）。该属的2个种，分别为C. auratus和C.食含有有毒强心内酯的植物。这些甲虫不仅可以避免毒素中毒，还可以利用毒素来防御捕食者。所有其他的Chrysochus物种都以缺乏Cardenolides的植物为食。Cardenolides最重要的活性成分是它们能够结合并由此阻断负责维持细胞电位的普遍存在的Na+/K+-ATP酶。通过分析的DNA序列的推定哇巴因结合位点的α-亚基的Na+/K+-ATP酶基因的Chrysochus和它的近亲喂养的植物有或没有cardenolides，我们在这里跟踪cardenolides不敏感性在这组甲虫的进化。序列之间最有趣的差异涉及第122位的氨基酸。然而，所有没有遇到Cardenolides的物种在这个位置都有天冬酰胺，而以Cardenolides植物为食的Chrysochus物种都有组氨酸。这种单一的氨基酸取代已经被证明会使帝王蝶对Cardenoprotein不敏感。基于线粒体DNA的同源性证实了这样的假设，即在果蝇和其他昆虫中观察到的Na+/K+-ATP酶基因α-亚基122位的天冬酰胺是这组叶甲中的近晶条件。在C. auratus和C. cobaltinus与哇巴因结合位点中天冬酰胺与组氨酸的交换相一致。
Herbivores that feed on toxic plants must overcome plant defenses and occasionally may even benefit from them. The current challenge is to understand how herbivores evolve the necessary physiological adaptations and which changes at the molecular level are involved. In this context we studied the leaf beetles genus Chrysochus (Coleoptera, Chrysomelidae). Two species of this genus, C. auratus and C. cobaltinus, feed on plants that contain toxic cardenolides. These beetles not only avoid poisoning by the toxin but also use it for their own defense against predators. All other Chrysochus species feed on plants that are devoid of cardenolides. The most important active principle of cardenolides is their capacity to bind to and thereby block the ubiquitous Na+/K+-ATPase responsible for maintaining cellular potentials. By analyzing the DNA sequence of the putative ouabain-binding site of the alpha-subunit of the Na+/K+-ATPase gene of Chrysochus and its close relatives feeding on plants with or without cardenolides, we here trace the evolution of cardenolide insensitivity in this group of beetles. The most interesting difference among the sequences involves the amino acid at position 122. Whereas all species that do not encounter cardenolides have an asparagine in this position, both Chrysochus species that feed on cardenolide plants have a histidine instead. This single amino acid substitution has already been shown to confer cardenolide insensitivity in the monarch butterfly. A mtDNA-based phylogeny corroborates the hypothesis that the asparagine at position 122 of the alpha-subunit of the Na+/K+-ATPase gene as observed in Drosophila and other insects is the plesiomorphic condition in this group of leaf beetles. The later host-plant switch to cardenolide-containing plants in the common ancestor of C. auratus and C. cobaltinus coincides with the exchange of the asparagine for a histidine in the ouabain binding site.