ETH Zurich, Institute of Integrative Biology (IBZ), ETH-Zentrum CHN, Universitätsstrasse 16, CH-8092 Zurich, Switzerland.
ETH Zurich, Institute of Integrative Biology (IBZ), ETH-Zentrum CHN, Universitätsstrasse 16, CH-8092 Zurich, Switzerland.
Infect Genet Evol. 2017 Dec;56:125-132. doi: 10.1016/j.meegid.2017.11.019. Epub 2017 Nov 16.
The antagonistic relationship between parasites and their hosts is strongly influenced by genotype-by-genotype interactions. Defense against parasitism is commonly studied in the context of immune system-based mechanisms and, thus, the focus in the search for candidate genes in host-parasite interactions is often on immune genes. In this study, we investigated the association between prevalence of parasite infection and host mitochondrial DNA (mtDNA) haplotypes in two natural populations of bumblebees (Bombus terrestris). The two most common haplotypes of the host populations, termed A and B, differ by a single nonsynonymous nucleotide substitution within the coding region of cytochrome oxidase I, an important player in metabolic pathways. We screened infection by Nosema bombi, a common endoparasite of bumblebees, and the corresponding host mtDNA-haplotype frequencies in over 1400 bumblebees between 2000 and 2010. The island population of Gotland showed lower mtDNA diversity compared to the mainland population in Switzerland. Over time, we observed large fluctuations in infection prevalence, as well as variation in host haplotype frequencies in both populations. Our long-term observation revealed that N. bombi infection of specific host genotypes is transient: We found that with increasing infection prevalence, proportionally more individuals with haplotype B, but fewer individuals with haplotype A were infected. This suggests that the presence of N. bombi in specific host genotypes relates to infection prevalence. This may be a result of parasite competition, or differential resilience of host types to ward off infections. The findings highlight the important role of host mtDNA haplotypes in the interaction with parasites.
寄生虫与其宿主之间的拮抗关系强烈受到基因型-基因型相互作用的影响。防御寄生虫通常是在免疫系统为基础的机制的背景下进行研究，因此，在宿主-寄生虫相互作用中寻找候选基因的重点通常是在免疫基因上。在这项研究中，我们调查了两个野生蜜蜂（Bombus terrestris）种群中寄生虫感染的流行率与宿主线粒体 DNA（mtDNA）单倍型之间的关联。宿主种群的两个最常见的单倍型，称为 A 和 B，在细胞色素氧化酶 I 的编码区域内有一个单一的非同义核苷酸取代，这是代谢途径中的一个重要参与者。我们筛选了蜜蜂常见的内寄生虫 Nosema bombi 的感染情况，以及在 2000 年至 2010 年间，超过 1400 只蜜蜂的相应宿主 mtDNA-单倍型频率。与瑞士的大陆种群相比，哥特兰岛种群的 mtDNA 多样性较低。随着时间的推移，我们观察到感染流行率的大幅波动，以及两个种群中宿主单倍型频率的变化。我们的长期观察表明，特定宿主基因型的 N. bombi 感染是短暂的：我们发现，随着感染流行率的增加，具有单倍型 B 的个体比例增加，但具有单倍型 A 的个体比例减少。这表明，特定宿主基因型中 N. bombi 的存在与感染流行率有关。这可能是寄生虫竞争的结果，或者是宿主类型对抵御感染的不同抵抗力的结果。这些发现强调了宿主 mtDNA 单倍型在与寄生虫相互作用中的重要作用。
