Our understanding of the vertebrate immune system is dominated by a few model organisms such as mice. This use of a few model systems is reasonable if major features of the immune systems evolve slowly and are conserved across most vertebrates, but may be problematic if there is substantial macroevolutionary change in immune responses. Here, we present a test of the macroevolutionary stability, across 15 species of jawed fishes, of the transcriptomic response to a standardized immune challenge. Intraperitoneal injection of an immune adjuvant (alum) induces a fibrosis response in nearly all jawed fishes, which in some species contributes to anti-helminth resistance. Despite this conserved phenotypic response, the underlying transcriptomic response is highly inconsistent across species. Although many gene orthogroups exhibit differential expression between saline versus alum-injected fish in at least one species, few orthogroups exhibit consistent differential expression across species. This result suggests that although the phenotypic response to alum (fibrosis) is highly conserved, the underlying gene regulatory architecture is very flexible and cannot readily be extrapolated from any one species to fishes (or vertebrates) more broadly. The vertebrate immune response is remarkably changeable over macroevolutionary time, requiring a diversity of model organisms to describe effectively.

• Klíčová slova
• evolutionary immunology, fibrosis, transcriptome,
• Publikační typ
• časopisecké články MeSH
• preprinty MeSH

The genes of the major histocompatibility complex (MHC) are an essential component of the vertebrate immune system and MHC genotypes may determine individual susceptibility to parasite infection. In the wild, selection that favors MHC variability can create situations in which interspecies hybrids experience a survival advantage. In a wild system of two naturally hybridizing leuciscid fish, we assessed MHC IIB genetic variability and its potential relationships to hosts' ectoparasite communities. High proportions of MHC alleles and parasites were species-specific. Strong positive selection at specific MHC codons was detected in both species and hybrids. MHC allele expression in hybrids was slightly biased towards the maternal species. Controlling for a strong seasonal effect on parasite communities, we found no clear associations between host-specific parasites and MHC alleles or MHC supertypes. Hybrids shared more MHC alleles with the more MHC-diverse parental species, but expressed intermediate numbers of MHC alleles and positively selected sites. Hybrids carried significantly fewer ectoparasites than either parent species, suggesting a hybrid advantage via potential heterosis.

• MeSH
• alely * MeSH
• Bayesova věta MeSH
• biologická evoluce * MeSH
• biologické modely MeSH
• Cyprinidae genetika   MeSH
• hlavní histokompatibilní komplex MeSH
• hybridizace genetická * MeSH
• hybridní efekt * genetika   MeSH
• křížení genetické MeSH
• lineární modely MeSH
• selekce (genetika) * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The genes of major histocompatibility complex (MHC) provide an excellent opportunity to study host-parasite relationships because they are expected to evolve in response to parasites and variation in parasite communities. In this study, we investigated the potential role of parasite-mediated selection acting on MHC class IIB (DAB) genes in European chub (Squalius cephalus) natural populations. We found significant differences between populations in metazoan parasites, neutral and adaptive genetic diversities. The analyses based on pairwise data revealed that populations with dissimilar MHC allelic profiles were geographically distant populations with significantly different diversity in microsatellites and a dissimilar composition of parasite communities. The results from the generalized estimating equations method (GEE) on the level of individuals revealed that metazoan parasite load in European chub was influenced by the diversity of DAB alleles as well as by the diversity of neutral genetic markers and host traits reflecting condition and immunocompetence. The multivariate co-inertia analysis showed specific associations between DAB alleles and parasite species. DAB1-like alleles were more involved in associations with ectoparasites, while DAB3-like alleles were positively associated with endoparasites which could suggest potential differences between DAB genes caused by different selection pressure. Our study revealed that parasite-mediated selection is not the only variable affecting MHC diversity in European chub; however, we strongly support the role of neutral processes as the main driver of DAB diversity across populations. In addition, our study contributes to the understanding of the evolution of MHC genes in wild living fish.

• Klíčová slova
• Genetic diversity, Major histocompatibility complex, Metazoan parasites, Microsatellites, Parasite-driven balancing selection, Phylogeography,
• MeSH
• alely MeSH
• Cyprinidae genetika   MeSH
• divoká zvířata MeSH
• genetická variace * MeSH
• hlavní histokompatibilní komplex genetika   MeSH
• interakce hostitele a parazita MeSH
• mikrosatelitní repetice genetika   MeSH
• nemoci ryb parazitologie   MeSH
• parazitární nemoci u zvířat epidemiologie   genetika   parazitologie   MeSH
• paraziti MeSH
• selekce (genetika) * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Evropa epidemiologie   MeSH

BACKGROUND: The Major Histocompatibility Complex (MHC) is a genomic region containing genes with crucial roles in immune responses. MHC class I and class II genes encode antigen-presenting molecules expressed on the cell surface. To counteract the high variability of pathogens, the MHC evolved into a region of considerable heterogeneity in its organization, number and extent of polymorphism. Studies of MHCs in different model species contribute to our understanding of mechanisms of immunity, diseases and their evolution. Camels are economically important domestic animals and interesting biomodels. Three species of Old World camels have been recognized: the dromedary (Camelus dromedarius), Bactrian camel (Camelus bactrianus) and the wild camel (Camelus ferus). Despite their importance, little is known about the MHC genomic region, its organization and diversity in camels. The objectives of this study were to identify, map and characterize the MHC region of Old World camelids, with special attention to genetic variation at selected class MHC II loci. RESULTS: Physical mapping located the MHC region to the chromosome 20 in Camelus dromedarius. Cytogenetic and comparative analyses of whole genome sequences showed that the order of the three major sub-regions is "Centromere - Class II - Class III - Class I". DRA, DRB, DQA and DQB exon 2 sequences encoding the antigen binding site of the corresponding class II antigen presenting molecules showed high degree of sequence similarity and extensive allele sharing across the three species. Unexpectedly low extent of polymorphism with low numbers of alleles and haplotypes was observed in all species, despite different geographic origins of the camels analyzed. The DRA locus was found to be polymorphic, with three alleles shared by all three species. DRA and DQA sequences retrieved from ancient DNA samples of Camelus dromedarius suggested that additional polymorphism might exist. CONCLUSIONS: This study provided evidence that camels possess an MHC comparable to other mammalian species in terms of its genomic localization, organization and sequence similarity. We described ancient variation at the DRA locus, monomorphic in most species. The extent of molecular diversity of MHC class II genes seems to be substantially lower in Old World camels than in other mammalian species.

• MeSH
• alely MeSH
• exony MeSH
• fylogeneze MeSH
• fyzikální mapování chromozomů MeSH
• geny MHC třídy II * MeSH
• haplotypy MeSH
• molekulární sekvence - údaje MeSH
• polymorfismus genetický * MeSH
• sekvence nukleotidů MeSH
• velbloudi genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: The gibel carp is a fish species with dual reproduction modes, gynogenesis and sexual reproduction, coexisting in mixed diploid-polyploid populations. Following the Red Queen (RQ) assumption, asexual organisms are, due to their low genetic diversity, targets for parasite adaptation. Because MHC polymorphism is maintained by selection from parasites and sexual selection, MHC genes are considered as a suitable candidate for testing the RQ hypothesis. In this study, we investigated MHC variability and the selection pressure acting on MHC genes in sexual diploids and asexual triploids. In addition, we tested whether the asexual form of gibel carp suffers from higher parasite loads than the sexual form. RESULTS: At the population level, genotype and allelic diversity of MHC were reduced in gynogenetic triploids when compared to sexual diploids. Different patterns in positively selected sites (PSS) between gynogens and sexual gibel carp were also found. A weak difference in parasite species richness was found between sexual fish and gynogens. However, two common clones of gynogens were significantly more parasitized than sexual diploids or other gynogens with rare MHC genotypes. At the individual level, the higher number of alleles was not associated with higher parasitism in either sexual diploids or gynogens. CONCLUSIONS: The differences in MHC diversity between gynogenetic triploids and sexual diploids are in accordance with the hypothesis of sexually-mediated selection increasing MHC diversity and fulfil a prerequisite of the Red Queen hypothesis. The different patterns in PSS between gynogens and sexual gibel carp also suggest the potential role of sexual selection and supports parasite-mediated selection maintaining MHC diversity. We showed that the most common MHC genotypes of gynogenetic triploids are the target of parasite selection. Our results suggest that the MHC genotype in gibel carp is more important than allelic number for immunocompetence.

• MeSH
• diploidie * MeSH
• genetická variace MeSH
• genotyp MeSH
• hlavní histokompatibilní komplex * MeSH
• kapři genetika   fyziologie   MeSH
• rozmnožování * MeSH
• rybí proteiny genetika   MeSH
• triploidie * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• rybí proteiny MeSH

The polymorphism of exon 2 of the DAB genes (major histocompatibility complex [MHC] class IIB) was investigated for the first time in the freshwater cyprinid fish species, Squalius cephalus, in the wide range of its distribution in Europe. We identified 111 different MHC class IIB variants in 15 chub populations distributed from Finland to Spain. The sequence analysis showed that many structurally important amino acid sites that were conserved among tetrapods were also conserved in chub. The analysis of recombination indicated that it does not play an important role in producing and maintaining the variation of DAB genes analyzed in the present study. The exon 2 was shown to be subjected to intense positive selection. Phylogenetic analysis and sequence identities suggest the presence of two class IIB loci (DAB1-like and DAB3-like) in chub. Nevertheless, the presence of three DAB3-like sequence variants in several individuals indicates the duplication of the DAB3 gene. A contrasting selection pattern was found in DAB1-like and DAB3-like genes, which suggests the potential functional differences between these genes. Some DAB sequence variants were shared among the populations of different mtDNA lineages. The phylogenetic analyses did not confirm any biogeographical pattern of the genetic structure of MHC IIB in chub, which is in line with balancing selection and trans-species polymorphism in MHC genes. Nevertheless, cluster analysis based on the presence/absence of DAB sequence variants in the populations showed the phylogeophraphical pattern corresponding to the mtDNA lineages, which indicates that neutral selection can partially explain the MHC IIB evolution in chub.

• MeSH
• Cyprinidae genetika   imunologie   MeSH
• exony MeSH
• geny MHC třídy II * MeSH
• molekulární evoluce * MeSH
• polymorfismus genetický MeSH
• selekce (genetika) MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Evropa MeSH