Fischer Hanna M, Wheat Christopher W, Heckel David G, Vogel Heiko
Department of Entomology, Max-Planck-Institute for Chemical Ecology, Beutenberg Campus, Jena, Germany.
Mol Biol Evol. 2008 May;25(5):809-20. doi: 10.1093/molbev/msn014. Epub 2008 Feb 23.
Chemical interactions between plants and their insect herbivores provide an excellent opportunity to study the evolution of species interactions on a molecular level. Here, we investigate the molecular evolutionary events that gave rise to a novel detoxifying enzyme (nitrile-specifier protein [NSP]) in the butterfly family Pieridae, previously identified as a coevolutionary key innovation. By generating and sequencing expressed sequence tags, genomic libraries, and screening databases we found NSP to be a member of an insect-specific gene family, which we characterized and named the NSP-like gene family. Members consist of variable tandem repeats, are gut expressed, and are found across Insecta evolving in a dynamic, ongoing birth-death process. In the Lepidoptera, multiple copies of single-domain major allergen genes are present and originate via tandem duplications. Multiple domain genes are found solely within the brassicaceous-feeding Pieridae butterflies, one of them being NSP and another called major allergen (MA). Analyses suggest that NSP and its paralog MA have a unique single-domain evolutionary origin, being formed by intragenic domain duplication followed by tandem whole-gene duplication. Duplicates subsequently experienced a period of relaxed constraint followed by an increase in constraint, perhaps after neofunctionalization. NSP and its ortholog MA are still experiencing high rates of change, reflecting a dynamic evolution consistent with the known role of NSP in plant-insect interactions. Our results provide direct evidence to the hypothesis that gene duplication is one of the driving forces for speciation and adaptation, showing that both within- and whole-gene tandem duplications are a powerful force underlying evolutionary adaptation.
植物与其植食性昆虫之间的化学相互作用为在分子水平上研究物种相互作用的进化提供了绝佳机会。在此，我们研究了导致粉蝶科出现一种新型解毒酶（腈特异性蛋白 [NSP]）的分子进化事件，该酶先前被确定为一种协同进化的关键创新因素。通过生成和测序表达序列标签、基因组文库以及筛选数据库，我们发现 NSP 是昆虫特异性基因家族的一员，我们对该家族进行了表征并命名为 NSP 样基因家族。其成员由可变串联重复序列组成，在肠道中表达，并且在昆虫纲中广泛存在，以动态的、持续的生灭过程进化。在鳞翅目中，存在单结构域主要变应原基因的多个拷贝，它们通过串联重复产生。多结构域基因仅在以十字花科植物为食的粉蝶科蝴蝶中发现，其中之一是 NSP，另一个称为主要变应原（MA）。分析表明，NSP 及其旁系同源物 MA 具有独特的单结构域进化起源，由基因内结构域重复后再进行串联全基因重复形成。重复基因随后经历了一段松弛的约束期，之后约束增加，可能是在新功能化之后。NSP 及其直系同源物 MA 仍在经历高变化率，这反映了与 NSP 在植物 - 昆虫相互作用中已知作用一致的动态进化。我们的结果为基因重复是物种形成和适应的驱动力之一这一假说提供了直接证据，表明基因内和全基因串联重复都是进化适应的强大力量。
