The Evolution of Extreme Genetic Variability in a Parasite-Resistance Complex

• DOI: 10.1093/gbe/evae222
• Publication Date: 2024-10-11T08:56:36Z
• Authors: Suha Naser-Khdour; Fabian Scheuber; Peter D Fields; Dieter Ebert
• Keywords: Indel; Balancing selection; Nucleotide diversity

Genomic regions that play a role in parasite defense are often found to be highly variable, with the major histocompatibility complex serving as an iconic example. Single nucleotide polymorphisms may represent only small portion of this variability, Indel and copy number variation further contributing. In extreme cases, haplotypes no longer recognized orthologous. Understanding evolution such divergent is challenging because most not visible using reference-assisted genomic approaches. Here we analyze case Pasteuria Resistance Complex crustacean Daphnia magna, host against common virulent bacterium ramosa. Two region have been previously described, parts it being nonhomologous, has shown under balancing selection. Using pan-genome analysis tree reconciliation methods explore its characteristics within between species other Cladoceran species, our revealed remarkable diversity even among many nonhomologous hyper-divergent haplotypes. The characterized by extensive duplication losses Fucosyltransferase (FuT) Galactosyltransferase (GalT) genes believed defense. can traced back ancestors over 250 million years. unique combination ancient resistance dynamic, environment presents fascinating opportunity investigate long-term maintenance polymorphisms. Our findings offer valuable insights into evolutionary forces shaping disease adaptation, genus Daphnia, but potentially across entire Cladocera class.