Roudel Mathieu, Aufauvre Julie, Corbara Bruno, Delbac Frederic, Blot Nicolas
Clermont Université, Université Blaise Pascal, Laboratoire Microorganismes: Génome et Environnement, BP 10448, 63000 Clermont-Ferrand, France.
Parasitology. 2013 Sep;140(11):1346-56. doi: 10.1017/S0031182013001133. Epub 2013 Jul 23.
The microsporidian parasite Nosema ceranae is a common pathogen of the Western honeybee (Apis mellifera) whose variable virulence could be related to its genetic polymorphism and/or its polyphenism responding to environmental cues. Since the genotyping of N. ceranae based on unique marker sequences had been unsuccessful, we tested whether a multilocus approach, assessing the diversity of ten genetic markers – encoding nine proteins and the small ribosomal RNA subunit – allowed the discrimination between N. ceranae variants isolated from single A. mellifera individuals in four distant locations. High nucleotide diversity and allele content were observed for all genes. Most importantly, the diversity was mainly present within parasite populations isolated from single honeybee individuals. In contrast the absence of isolate differentiation precluded any taxa discrimination, even through a multilocus approach, but suggested that similar populations of parasites seem to infect honeybees in distant locations. As statistical evolutionary analyses showed that the allele frequency is under selective pressure, we discuss the origin and consequences of N. ceranae heterozygosity in a single host and lack of population divergence in the context of the parasite natural and evolutionary history.
微孢子虫寄生虫蜜蜂微孢子虫是西方蜜蜂（意大利蜜蜂）的常见病原体，其毒力的变化可能与其遗传多态性和/或对环境线索作出反应的多型现象有关。由于基于独特标记序列对蜜蜂微孢子虫进行基因分型未获成功，我们测试了一种多位点方法，评估十个遗传标记（编码九种蛋白质和小核糖体RNA亚基）的多样性，是否能够区分从四个不同地点的单个意大利蜜蜂个体分离出的蜜蜂微孢子虫变体。所有基因均观察到高核苷酸多样性和等位基因含量。最重要的是，这种多样性主要存在于从单个蜜蜂个体分离出的寄生虫种群中。相比之下，即使通过多位点方法也无法进行分离株鉴别，这表明在不同地点似乎有相似的寄生虫种群感染蜜蜂。由于统计进化分析表明等位基因频率处于选择压力之下，我们在寄生虫自然和进化史的背景下，讨论了单个宿主中蜜蜂微孢子虫杂合性的起源和后果以及缺乏种群分化的情况。
