Genomic organization of the major histocompatibility complex (MHC) can profoundly influence gene function and multigene family evolution. Situated at the interface of individual genetic variation and the adaptive immune response, MHC class I and II loci are intensively studied for disease associations and used as markers of adaptive genetic variation in evolutionary ecology research.
Genomic sequence of MHC-containing cosmid clones from the red-billed gull (Larus scopulinus, Charadriiformes: shorebirds, gulls, and allies) was obtained for comparative analysis of avian MHC evolution. MHCI polymorphism was further investigated using cDNA library screening and locus-specific genotyping protocols. This first information regarding MHC organization and MHCI variation in charadriiforms suggests a complex evolutionary history to MHC architecture in birds. Duplication of MHCIIα loci in tandem MHCIIα/β pairs and their proximity to MHC-region gene COL11A2 are similar to arrangements in nonavian vertebrates, and contrast with the “minimal essential” MHC of the chicken (Gallus gallus, Galliformes: gamebirds). MHCI–TAP2 organization is shared with Galloanserae (gamebirds + waterfowl), as is a proposed major classical function for this MHCI gene. In contrast, the placement of
MHCI genes adjacent to sequence from chromosomes 3, 5, and 22 of the chicken and zebra finch (Taeniopygia guttata, Passeriformes: perching birds) indicates interchromosomal rearrangements in birds and the possible genomic dispersal of nonclassical MHCI genes in the red-billed gull.
Screening for avian malaria, genetic parentage tests, and field data from red-billed gulls at Kaikoura Peninsula, New Zealand were combined with MHCI genotypes to investigate relationships with disease and reproduction. Plasmodium infection was confirmed in red-billed gulls, and breeding condition was negatively associated with malarial infection and positively related to variation at the putative major MHCI locus. A low rate of extrapair paternity was identified across thirteen breeding seasons. Partners without extrapair young (EPY) had greater MHCI dissimilarity than was expected by chance, whereas lower individual MHCI variation and elevated hatching failure existed for pairs with EPY. In addition to contributing to studies of MHC evolution, sexual selection, and disease dynamics in the New Zealand avifauna, this research will facilitate studies of MHC genes in related charadriiforms, many of which are of conservation concern.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/32301 |
| Date | 26 March 2012 |
| Creators | Cloutier, Alison J. |
| Contributors | Baker, Allan J. |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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