Evolution and ecology of parasitism and symbiosis in insects

昆虫寄生与共生的进化与生态学

• 批准号: RGPIN-2015-03768
• 负责人: Perlman, Steven
• 金额: $ 2.91万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=661963
• 关键词: Evolution; ecology; parasitism; symbiosis; insects

Symbiosis is one of the most important forces shaping life on our planet. A major recent development in biology is the realization that all multicellular organisms harbour symbiotic microbes. These have long been incredibly difficult to study; however, advances in molecular and computational biology have revolutionized our understanding of microbial symbiosis. For example, we are just beginning to disentangle the function of the trillions of microbes that live in the human gut, and their important roles in metabolism, immunity, and development. Indeed, it has been argued that one cannot consider the ecology and evolution of an organism without including its microbiota, viewing the organism as a `hologenome' (i.e. the host's nuclear, organellar, and symbiont genomes combined).***My research aims to understand the ecological and evolutionary consequences of symbiosis in insects. Virtually all insects are infected with inherited bacterial symbionts that are transmitted from mothers to their offspring, often in the egg cytoplasm, similar to mitochondria (themselves the descendants of an ancient symbiosis). In maternal transmission, host and symbiont fitness are tightly linked. Indeed, many insect inherited symbionts have evolved to increase the fitness of their hosts, for example by defending them against natural enemies. However, some inherited symbionts manipulate host reproduction to increase the frequency of females, for example by transforming male hosts into females that can then transmit more symbionts. These symbionts, termed `reproductive parasites', highlight the potential for conflicts between symbionts and hosts over transmission. A major aim of this proposal is to examine the consequences of this conflict, for example by asking whether inherited symbionts show reduced function in male hosts (since males are an evolutionary dead end). Tighter still is the link between inherited symbionts and mitochondria, and another major aim of this proposal is to understand how symbionts and mitochondria interact and affect one another, and whether there is co-adaptation between them. Finally, I will examine the effect that other selfish genetic elements that distort sex ratios have on symbionts and mitochondria.***I propose to study two insect model systems. The first, the mushroom-feeding fly Drosophila neotestacea, harbours a Spiroplasma bacterial symbiont that protects it against a virulent parasitic nematode. Due to this strong protective benefit, Spiroplasma is spreading rapidly across N. America. The second, the booklouse Liposcelis bostrychophila (a relative of parasitic lice), is polymorphic for an extraordinary maternally inherited sex-ratio distortion, with most females producing only daughters. Also, the mitochondrial genomes of distorting females are ~30% divergent and have a completely different gene order and genome structure than their `normal' counterparts.********

共生是塑造地球生命的最重要力量之一。最近生物学的一个主要发展是认识到所有多细胞生物都含有共生微生物。长期以来，这些都是非常难以研究的;然而，分子和计算生物学的进步已经彻底改变了我们对微生物共生的理解。例如，我们刚刚开始解开生活在人类肠道中的数万亿微生物的功能，以及它们在新陈代谢，免疫和发育中的重要作用。事实上，有人认为，如果不包括微生物，就不能考虑生物体的生态和进化，将生物体视为“全基因组”（即宿主的核、细胞器和共生体基因组的组合）。我的研究旨在了解昆虫共生的生态和进化后果。几乎所有的昆虫都感染了遗传的细菌共生体，这些共生体从母亲传给后代，通常在卵细胞质中，类似于线粒体（它们本身是古老共生体的后代）。在母体传播中，宿主和共生体的适应性是紧密相连的。事实上，许多昆虫遗传的共生体已经进化成增加宿主的适应性，例如通过保护它们免受天敌的侵害。然而，一些遗传的共生体操纵宿主繁殖以增加雌性的频率，例如通过将雄性宿主转化为雌性，然后可以传递更多的共生体。这些共生体被称为“生殖寄生物”，突出了共生体和宿主之间在传播方面发生冲突的可能性。这项提议的一个主要目的是研究这种冲突的后果，例如，通过询问遗传共生体是否在男性宿主中表现出功能降低（因为男性是进化的死胡同）。更紧密的是遗传共生体和线粒体之间的联系，该提案的另一个主要目的是了解共生体和线粒体如何相互作用和相互影响，以及它们之间是否存在共同适应。最后，我将研究其他扭曲性别比例的自私遗传因素对共生体和线粒体的影响。我打算研究两个昆虫模型系统。第一种是以蘑菇为食的果蝇（Drosophila neotestacea），它体内有一种螺原体细菌共生体，可以保护它免受有毒寄生线虫的侵害。由于这种强大的保护作用，螺原体在N.美国参考第二种是嗜卷书虱（Liposcelis bostrychophila，寄生虱的一种亲戚），它具有一种异常的母系遗传性性别比例畸变的多态性，大多数雌性只生女儿。此外，扭曲女性的线粒体基因组有约30%的差异，并且与“正常”对应物相比具有完全不同的基因顺序和基因组结构。