EF 03: Origin and Evolution of the Bracovirus-Braconid Wasp Symbiosis

蚕科中的许多寄生蜂在毛虫体内产卵，毛虫作为发育中的黄蜂后代的食物和家园后最终死亡。黄蜂与毛虫寄主之间的生理和内分泌相互作用具有很大的复杂性。在这方面，没有什么比黄蜂将病毒进化到它们的宿主操纵工具箱中更引人注目的了。这些病毒已完全整合到黄蜂的染色体DNA中，但功能基因仍被包装成“前病毒”，并与黄蜂的卵一起“输出”到毛虫体内。这些基因参与影响毛虫的免疫和内分泌系统，从而提高里面黄蜂幼虫的存活率。这个项目探索了黄蜂和病毒之间这种相互作用的令人难以置信的进化。这是已知的少数几个病毒和真核生物之间互利关系的案例之一，此外，值得注意的是，黄蜂的基因组如此相互交织，以至于病毒不再是一个独立的实体，而是作为一个内共生体，或多或少像线粒体和叶绿体一样。这个项目的设计包括比较黄蜂和病毒的系统发育(“进化树”)，从DNA序列的比较中推断出来，以探索黄蜂和病毒共同进化的时间。到目前为止，PI已经证明了在黄蜂的一个大属中，黄蜂和病毒的系统发育基本上是相同的，并且还表明携带病毒的黄蜂形成了单一的进化谱系。有待确定的是，在携带病毒的整个黄蜂群中，黄蜂和病毒的系统发育是否相同，以及这些病毒可能来自哪里(即，哪些其他病毒组可能是相关的)。随着最后两个问题的解决，关于这种非凡的联系是如何发展的更完整的图景将被揭示。这些结果不仅会引起进化生物学家的兴趣，而且很可能在设计复杂的控制毛虫害虫的策略方面具有实际意义。

Many parasitoid wasps in the family Braconidae lay their eggs inside the bodies of caterpillars, which ultimately die after serving as food and home for the developing wasp offspring. There is great complexity to the physiological and endocrine interactions between the wasp and its caterpillar host. No aspect of this is more remarkable than the evolutionary incorporation of viruses by the wasps into their toolkits of host manipulation. The bracoviruses are fully integrated into the wasp chromosomal DNA, yet functional genes are still packaged as "proviruses" and "exported" into the caterpillars along with the wasp eggs. These genes are involved in influencing the caterpillars' immune and endocrine systems in ways that enhance survival of the wasp larvae inside. This project explores the incredible evolution of this interaction between wasps and viruses. It is one of the few cases known of a mutually beneficial relationship between a virus and a eukaryotic organism, and in addition is remarkable in that the genomes of wasp are so intertwined that the viruses are no longer an independent entity, but instead act as an endosymbiont, more or less like mitochondria and chloroplasts. The design of this project involves comparing phylogenies ("evolutionary trees") of both wasps and viruses, inferred from comparisons of DNA sequences, to explore how long the wasps and viruses have been coevolving. So far the PI has demonstrated that the wasp and virus phylogenies are essentially identical within a large genus of the wasps, and have also shown that the wasps that carry the viruses form a single evolutionary lineage. Remaining to be determined is whether the wasp and virus phylogenies are identical through the whole wasp group that carries the viruses, and where these viruses may have come from (i. e., which other groups of viruses may be related). With the solution to these last two questions, a more complete picture of how this remarkable association developed will be revealed. The results will be of interest not only to evolutionary biologists, but may well have practical implications in terms of designing sophisticated control strategies against caterpillar pests.