美国加州大学伯克利分校Noah K. Whiteman小组的一项最新研究，利用基因组编辑技术追溯了帝王蝶的毒素抗性进化过程。相关论文2019年10月2日在线发表于国际学术期刊《自然》。

研究人员表示，确定适应性的遗传机制需要阐明DNA序列、表型和适应性之间的联系。趋同进化可以作为指导，以识别适应性状的候选突变，而新的基因组编辑技术正在促进整个生物中这些突变的功能验证。

研究人员结合了这些方法，研究了六个进化次序趋同进化的经典案例，其中包括帝王蝶（Danaus plexippus），它们已经独立进化成能够定殖产生强心苷毒素的植物。这些昆虫中的许多昆虫在心脏强心苷的生理学靶点钠泵（Na⁺/K⁺-ATPase）的α亚基（ATPα）中进化出平行的氨基酸替代残基。

研究人员描述了突变路径，其涉及与心脏糖苷特化有关的三个重复变化的ATPα氨基酸位点（第111、119和122位）。然后，研究人员对果蝇的天然Atpα基因进行了CRISPR–Cas9碱基编辑，并追溯了不同帝王蝶类型的突变路径。研究人员在体内、体外和计算机模拟中均证实了该途径赋予了对强心苷的抗药性和靶位不敏感，最终导致了三重突变体“帝王蝇”，它们对强心苷的敏感性不亚于帝王蝶。“帝王蝇”通过变态作用保留了少量的强心苷，这一特征已在帝王蝶中得到优化，来阻止天敌。通过上位性实现的拮抗多效性改善可以解释突变发生的顺序。

这项研究阐明了帝王蝶如何进化出对一类植物毒素的抵抗力，最终使自身变得难吃，并改变了生态群落内部物种相互作用的本质。

附：英文原文

Title: Genome editing retraces the evolution of toxin resistance in the monarch butterfly

Author: Marianthi Karageorgi, Simon C. Groen, Fidan Sumbul, Julianne N. Pelaez, Kirsten I. Verster, Jessica M. Aguilar, Amy P. Hastings, Susan L. Bernstein, Teruyuki Matsunaga, Michael Astourian, Geno Guerra, Felix Rico, Susanne Dobler, Anurag A. Agrawal, Noah K. Whiteman

Issue&Volume: 2019-10-02

Abstract: 

Identifying the genetic mechanisms of adaptation requires the elucidation of links between the evolution of DNA sequence, phenotype, and fitness1. Convergent evolution can be used as a guide to identify candidate mutations that underlie adaptive traits2,3,4, and new genome editing technology is facilitating functional validation of these mutations in whole organisms1,5. We combined these approaches to study a classic case of convergence in insects from six orders, including the monarch butterfly (Danaus plexippus), that have independently evolved to colonize plants that produce cardiac glycoside toxins6,7,8,9,10,11. Many of these insects evolved parallel amino acid substitutions in the α-subunit (ATPα) of the sodium pump (Na+/K+-ATPase)7,8,9,10,11, the physiological target of cardiac glycosides12. Here we describe mutational paths involving three repeatedly changing amino acid sites (111, 119 and 122) in ATPα that are associated with cardiac glycoside specialization13,14. We then performed CRISPR–Cas9 base editing on the native Atpα gene in Drosophila melanogaster flies and retraced the mutational path taken across the monarch lineage11,15. We show in vivo, in vitro and in silico that the path conferred resistance and target-site insensitivity to cardiac glycosides16, culminating in triple mutant ‘monarch flies’ that were as insensitive to cardiac glycosides as monarch butterflies. ‘Monarch flies’ retained small amounts of cardiac glycosides through metamorphosis, a trait that has been optimized in monarch butterflies to deter predators17,18,19. The order in which the substitutions evolved was explained by amelioration of antagonistic pleiotropy through epistasis13,14,20,21,22. Our study illuminates how the monarch butterfly evolved resistance to a class of plant toxins, eventually becoming unpalatable, and changing the nature of species interactions within ecological communities2,6,7,8,9,10,11,15,17,18,19.

DOI: 10.1038/s41586-019-1610-8

Source:https://www.nature.com/articles/s41586-019-1610-8