Experimental host-parasite coevolution in a changing environment

点击翻译按钮获取中文摘要

Theory predicts that stressors can have multiple effects on a host-parasite interaction either by increasing the number of hosts with decreased resistance or by reducing host abundance and consequently the transmission rate of the parasite. Likewise, stress can promote an increase or decrease of parasite virulence or pathogenicity. The so-called killer trait of the Paramecium / Caedibacter host-parasite system will be used to investigate these open questions. This killer trait of Paramecium tetraurelia is mediated by the vertically transmitted bacterial parasite Caedibacter taeniospiralis, which offers a selective competition advantage to its host. Infected paramecia release low amounts of their parasite into the medium. After ingestion by a parasite-free Paramecium, the bacterial killer-toxin kills the susceptible competitor of the host. Consequently, in this system the parasite can evolve towards increased or decreased pathogenicity. We propose to analyse the outcome of a long-term experimental co-evolution under heat stress. Particularly, we will investigate the hypothesis that stress increases parasite pathogenicity, which concomitantly fosters the evolution of a killer-toxin resistance in Paramecium. Further, we will test the hypothesis that the rapid evolution of the host is based on epigenetic changes and that the killer-toxin resistance is genotype specific. Combined experimental and molecular approaches will be used to understand the evolution of Paramecium’s killer-toxin resistance at a genomic level as well as the functional background of parasite pathogenicity.