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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612559
• 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.

共生是塑造我们星球生命的最重要力量之一。生物学最近的一个重大发展是认识到所有多细胞生物都具有共生微生物。这些长期以来很难研究。但是，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，我们才刚刚开始解散生活在人类肠道中的数万亿微生物的功能，及其在代谢，免疫学和发育中的重要作用。确实，有人认为，如果不包括其菌群，将生物体视为“全息素”（即宿主的核，有机和符号基因组），就不能考虑生物体的生态和进化。 我的研究旨在了解昆虫共生的生态和进化后果。几乎所有昆虫都被遗传的细菌符号感染，这些象征从母亲传播到其后代，通常在卵细胞质中，类似于线粒体（本身就是古代象征主义的后代）。在母体传播中，宿主和共生体健身紧密相连。实际上，许多昆虫继承的符号已经进化，以增加宿主的适应性，例如，捍卫它们免受天然敌人的侵害。但是，一些遗传的符号操纵宿主繁殖以增加女性的频率，例如，将男性宿主转化为可以传递更多符号的女性。这些符号称为“生殖寄生虫”，突出了符号与主机之间在传输上发生冲突的潜力。该建议的主要目的是检查这场冲突的后果，例如，询问继承的符号是否显示出男性宿主的功能降低（因为男性是进化的死胡同）。遗传符号和线粒体之间的联系仍然更加紧密，该提议的另一个主要目的是了解符号和线粒体如何相互作用和彼此影响，以及它们之间是否有共同适应。最后，我将研究性别比例对符号和线粒体的其他自私遗传元素的影响。 我建议研究两个绝缘模型系统。首先，肌肉喂养果蝇新疾病，藏有一种螺旋质细菌符号，可保护其免受毒力性寄生虫的侵害。由于这种强大的保护益处，螺旋藻正在跨美国迅速传播。第二个是书柜脂肪镜Boystrychophila（寄生虱子的亲戚），对于主要遗传性的性比例扭曲的非凡性，大多数女性仅产生女儿。同样，扭曲女性的线粒体基因组约为30％，具有与“正常”对应物的基因顺序和基因组结构完全不同。