Ecology, evolution, and genetics of parasitism and symbiosis in insects

昆虫寄生与共生的生态学、进化和遗传学

• 批准号: RGPIN-2020-06996
• 负责人: Perlman, Steven
• 金额: $ 4.74万
• 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: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=745849
• 关键词: Ecology; evolution; genetics; parasitism; symbiosis; Ecology; evolution; genetics; parasitism; symbiosis

Infection by pathogens and parasites is one of the most powerful threats that all organisms face, and is a major driver of innovation and rapid evolution. Indeed, organisms have evolved diverse defenses to deal with infection, including sophisticated immune systems and pathogen avoidance behaviours. My lab studies the evolution and ecology of host-parasite interactions, using insects as model hosts, and in this proposal, I will study the role of two pervasive but cryptic players - defensive symbionts and selfish genetic elements. Recently, we have come to appreciate that many organisms harbour beneficial microbes that protect them against harmful infections. Yet we do not have a good understanding of how important symbiont-mediated protection is in the wild, or how it interacts with other modes of defense, such as the immune system. Nor do we have a good understanding of how natural enemies counter-resist symbionts. We recently found that the common woodland fly, Drosophila neotestacea, harbours a strain of the bacterial symbiont Spiroplasma, that protects it against a virulent parasitic nematode. The benefit conferred by the symbiont is so great that symbiont-infected flies are rapidly spreading across N. America, and we will determine how this has affected the parasite and the various fly species it infects. Have nematodes evolved resistance to symbionts? Spiroplasma also protects hosts against parasitic wasps, and in parallel, we will determine whether this occurs and is important in the field. We have also discovered that the parasitic nematode itself harbours an obligate bacterial endosymbiont and we will determine its role in the fly-nematode interaction. Organisms also commonly harbour genomic parasites - also known as selfish genetic elements. These break the basic rules of Mendelian inheritance in order to gain a transmission advantage, often with negative fitness consequences. Selfish genetic elements are pervasive burdens on host genomes but they are much less studied because they are cryptic and often suppressed by the rest of the genome. One of the most striking types of selfish genetic elements are selfish X chromosomes, whereby males that carry a selfish X chromosome produce a gene product that destroys Y-bearing sperm, siring almost exclusively daughters. This sex ratio distortion can have drastic population consequences. How do selfish X chromosomes persist over evolutionary time? Do they have other fitness consequences? How does the rest of the genome suppress them? What is the mode of action of selfishness and resistance to it? We recently discovered a selfish X chromosome, as well as an autosomal gene that suppresses it, in D. testacea (the sister species of D. neotestacea) and we will answer these questions, using both ecological and genomic approaches.

病原体和寄生虫感染是所有生物所面临的最强大威胁之一，并且是创新和快速发展的主要驱动力。实际上，生物体已经发展出多种防御能力来应对感染，包括复杂的免疫系统和病原体避免行为。我的实验室研究了使用昆虫作为模型宿主的宿主 - 寄生虫相互作用的进化和生态，在此提案中，我将研究两个普遍但隐秘的玩家的作用 - 防御性共生体和自私的遗传元素。最近，我们已经意识到，许多生物具有保护它们免受有害感染的有益微生物。然而，我们对共生体介导的保护在野外的重要性或与其他防御模式（例如免疫系统）的相互作用方式没有很好的了解。我们也没有很好地了解自然敌人如何对抗抗拒的共生体。我们最近发现，普通的林地蝇果蝇Neotestacea含有细菌共生螺旋体的菌株，可保护其免受强大的寄生虫线虫的侵害。共生体赋予的益处是如此之大，以至于共生菌感染的果蝇迅速传播在美国，我们将确定这如何影响寄生虫及其感染的各种蝇物种。线虫是否进化出对共生体的抗性？螺旋体还可以保护宿主免受寄生黄蜂的影响，同时，我们将确定这是否发生并且在田间很重要。我们还发现，寄生线虫本身具有强大的细菌内共生菌，我们将确定其在蝇螺旋相互作用中的作用。生物体通常也藏有基因组寄生虫 - 也称为自私遗传元素。这些打破了孟德尔继承的基本规则，以获得传输优势，通常会带来负面影响。自私的遗传元素对宿主基因组普遍存在，但研究得多，因为它们是神秘的，并且经常被其余基因组所抑制。自私的遗传元素最引人注目的类型之一是自私的X染色体，其中携带自私的X染色体的雄性会产生一种破坏Y含Y的精子的基因产物，几乎只有女儿。这种性别比扭曲可能会带来巨大的人口后果。自私的X染色体如何在进化时代持续存在？他们还有其他健身后果吗？其余的基因组如何抑制它们？自私和抵抗的行动方式是什么？我们最近在D. testacea（Neotestacea的姊妹种类）中发现了一种自私的X染色体以及一种抑制它的常染色体基因，我们将使用生态和基因组方法来回答这些问题。