A population study of killer viruses reveals different evolutionary histories of two closely related Saccharomyces sensu stricto yeasts

Microbes have evolved ways of interference competition to gain advantage over their ecological competitors. The use of secreted killer toxins by yeast cells through acquiring double-stranded RNA viruses is one such prominent example. Although the killer behaviour has been well studied in laboratory yeast strains, our knowledge regarding how killer viruses are spread and maintained in nature and how yeast cells co-evolve with viruses remains limited. We investigated these issues using a panel of 81 yeast populations belonging to three Saccharomyces sensu stricto species isolated from diverse ecological niches and geographic locations. We found that killer strains are rare among all three species. In contrast, killer toxin resistance is widespread in Saccharomyces paradoxus populations, but not in Saccharomyces cerevisiae or Saccharomyces eubayanus populations. Genetic analyses revealed that toxin resistance in S. paradoxus is often caused by dominant alleles that have independently evolv...微生物已演化出干扰竞争（interference competition）策略，以在与生态竞争者的角逐中获取优势。酵母菌细胞通过获取双链RNA病毒（double-stranded RNA virus）并分泌杀伤毒素（killer toxin），便是这类策略的典型例证之一。尽管学界已对实验室酵母菌株中的杀伤表型开展了充分研究，但我们对于杀伤病毒在自然环境中的传播与维持机制，以及酵母菌与病毒的协同演化过程，仍知之甚少。本研究以从多样生态位与地理区域中分离得到的、隶属于3个狭义酿酒酵母类群（Saccharomyces sensu stricto）物种的81个酵母菌种群为研究材料，针对上述问题展开探究。研究发现，在这3个物种中，杀伤型酵母菌均较为罕见。与之形成鲜明对比的是，杀伤毒素抗性在帕拉普酿酒酵母（Saccharomyces paradoxus）种群中广泛存在，但在酿酒酵母（Saccharomyces cerevisiae）与真贝酿酒酵母（Saccharomyces eubayanus）种群中则并非如此。遗传分析显示，帕拉普酿酒酵母的毒素抗性通常由显性等位基因介导，且这些等位基因经独立演化...