Abstracts (first author)
Evolution of Daphnia magna resistance to the pathogen Pasteuria ramosa
Crustaceans of the genus Daphnia have long been used as models in studies of ecology and evolution and of host-pathogen coevolution in particular. However, little is known about the genetic and molecular basis of Daphnia resistance to pathogens. A well-known ecology combined with recent advances in genomic, genetic and molecular tools make Daphnia crustaceans, and in particular Daphnia magna and Daphnia pulex, remarkable models for modern evolution and ecology. D. magna is colonized by a wide range of parasites and pathogens, among them the bacterium Pasteuria ramosa. The study of inheritance patterns of resistance and susceptibility of D. magna clones to different P. ramosa genetic isolates reveals strong genotype-to-genotype interactions, suggesting coevolution between host and pathogen populations. Resistance and susceptibility of D. magna to different P. ramosa isolates follow mendelian patterns of inheritance and segregation, suggesting that a small number of loci underlie natural variation in D. magna resistance to P. ramosa infection. A F2 panel of D. magna was generated, with more than 200 genotypes that are kept by clonal reproduction. A QTL analysis revealed one genomic region of 150kb in linkage group 4 that explaining approximately 60% of the observed variation. However, further inheritance analysis showed that at least 3 loci underlie natural variation in D. magna resistance to P. ramosa infection. One of those loci corresponds to an indel of approximately 50kb. We are currently fine-mapping the QTL interval to identify genes and polymorphisms underlying Daphnia resistance to Pasteuria. We aim to identify which genes and networks and which polymorphisms underlie the natural variation and evolution of pathogen resistance in D. magna. We plan to use molecular tools recently developed for D. magna to achieve our objectives.