Copy numbers of stress response genes reflect difference in adaptive potential of metazoan parasites

Abstract

Stress responses are key for parasite survival and, thus, also the evolutionary success of these organisms. However, the evolution of the molecular pathways dealing with environmental stressors are poorly understood as most research focuses either on few selected human-relevant pathogens or major parasite clades. Here, we comparatively investigate, for the first time, antioxidant, heat shock, and behaviour-related genes in the two parasite lineages Cichlidogyrus and Kapentagyrus from the same family Dactylogyridae through whole-genome sequencing data of 11 species. The two lineages differ concerning their species and ecological diversity, which is expected to affect the diversity of their stress responses and, hence, their adaptive potential. Through an exon bait capture approach, we assembled the putative protein sequences of 43 stress-related genes. We discovered that Cichlidogyrus presented higher copy numbers of stress genes (70 kDA heat shock protein, glutathione S-transferase genes) than Kapentagyrus. This difference might explain the ability of species of Cichlidogyrus to colonise various cichlid and non-cichlid lineages. In comparison to most other organisms studied so far, we also observed a previously unreported absence of cytochrome P450 and sigma class glutathione S-transferase in monogenean flatworms. This pattern aligns with previously published genome annotations of monogeneans.