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RISS 인기검색어
- 검색키워드
- 저자 : Kosch, Tiffany A. (검색결과 4 건)
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Kosch, Tiffany A.,Bataille, Arnaud,Didinger, Chelsea,Eimes, John A.,Rodrí,guez-Brenes, Sofia,Ryan, Michael J.,Waldman, Bruce The Royal Society 2016 Biology letters Vol.12 No.8
<P> Pathogen-driven selection can favour major histocompatibility complex (MHC) alleles that confer immunological resistance to specific diseases. However, strong directional selection should deplete genetic variation necessary for robust immune function in the absence of balancing selection or challenges presented by other pathogens. We examined selection dynamics at one MHC class II (MHC-II) locus across Panamanian populations of the túngara frog, <I>Physalaemus pustulosus</I> , infected by the amphibian chytrid fungus <I>Batrachochytrium dendrobatidis</I> (Bd). We compared MHC-II diversity in highland túngara frog populations, where amphibian communities have experienced declines owing to Bd, with those in the lowland region that have shown no evidence of decline. Highland region frogs had MHC variants that confer resistance to Bd. Variant fixation appeared to occur by directional selection rather than inbreeding, as overall genetic variation persisted in populations. In Bd-infected lowland sites, however, selective advantage may accrue to individuals with only one Bd-resistance allele, which were more frequent. Environmental conditions in lowlands should be less favourable for Bd infection, which may reduce selection for specific Bd resistance in hosts. Our results suggest that MHC selection dynamics fluctuate in túngara frog populations as a function of the favourability of habitat to pathogen spread and the vulnerability of hosts to infection. </P>
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Characterization of MHC class IA in the endangered southern corroboree frog
Kosch, Tiffany A.,Eimes, John A.,Didinger, Chelsea,Brannelly, Laura A.,Waldman, Bruce,Berger, Lee,Skerratt, Lee F. Springer-Verlag 2017 Immunogenetics Vol.69 No.3
<P>Southern corroboree frogs (Pseudophryne corroboree) have declined to near extinction in the wild after the emergence of the amphibian chytrid fungus Batrachochytrium dendrobatidis in southeastern Australia in the 1980s. A major captive breeding and reintroduction program is underway to preserve this iconic species, but improving resistance to B. dendrobatidis would help the wild population to be self-sustaining. Using 3' and 5' rapid amplification of complementary DNA ends (RACE), we characterized the major histocompatibility complex (MHC) class IA locus in this species. We then used sequences generated from RACE to design primers to amplify the peptide-binding region (PBR) of this functional genetic marker. Finally, we analysed the diversity, phylogeny, and selection patterns of PBR sequences from four P. corroboree populations and compared this with other amphibian species. We found moderately high MHC class IA genetic diversity in this species and evidence of strong positive and purifying selection at sites that are associated with putative PBR pockets in other species, indicating that this gene region may be under selection for resistance to Bd. Future studies should focus on identifying alleles associated with Bd resistance in P. corroboree by performing a Bd laboratory challenge study to confirm the functional importance of our genetic findings and explore their use in artificial selection or genetic engineering to increase resistance to chytridiomycosis.</P>
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Recent Asian origin of chytrid fungi causing global amphibian declines
O’Hanlon, Simon J.,Rieux, Adrien,Farrer, Rhys A.,Rosa, Goncalo M.,Waldman, Bruce,Bataille, Arnaud,Kosch, Tiffany A.,Murray, Kris A.,Brankovics, Balá,zs,Fumagalli, Matteo,Martin, Michael D.,Wales American Association for the Advancement of Scienc 2018 Science Vol.360 No.6389
<P>Globalized infectious diseases are causing species declines worldwide, but their source often remains elusive. We used whole-genome sequencing to solve the spatiotemporal origins of themost devastating panzootic to date, caused by the fungus Batrachochytrium dendrobatidis, a proximate driver of global amphibian declines. We traced the source of B. dendrobatidis to the Korean peninsula, where one lineage, BdASIA-1, exhibits the genetic hallmarks of an ancestral population that seeded the panzootic. We date the emergence of this pathogen to the early 20th century, coinciding with the global expansion of commercial trade in amphibians, and we show that intercontinental transmission is ongoing. Our findings point to East Asia as a geographic hotspot for B. dendrobatidis biodiversity and the original source of these lineages that now parasitize amphibians worldwide.</P>
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Dufresnes, Christophe,Borz?e, Ama?l,Horn, Agn?s,St?ck, Matthias,Ostini, Massimo,Sermier, Roberto,Wassef, J?r?me,Litvinchuck, Spartak N,Kosch, Tiffany A,Waldman, Bruce,Jang, Yikweon,Brelsford, Alan,Per University of Chicago Press 2015 Molecular biology and evolution Vol.32 No.9
<P>Contrasting with birds and mammals, poikilothermic vertebrates often have homomorphic sex chromosomes, possibly resulting from high rates of sex-chromosome turnovers and/ or occasional X-Y recombination. Strong support for the latter mechanism was provided by four species of European tree frogs, which inherited from a common ancestor (similar to 5Ma) the same pair of homomorphic sex chromosomes (linkage group 1, LG1), harboring the candidate sex-determining gene Dmrt1. Here, we test sex linkage of LG1 across six additional species of the Eurasian Hyla radiation with divergence times ranging from 6 to 40 Ma. LG1 turns out to be sex linked in six of nine resolved cases. Mapping the patterns of sex linkage to the Hyla phylogeny reveals several transitions in sex-determination systems within the last 10My, including one switch in heterogamety. Phylogenetic trees of DNA sequences along LG1 are consistent with occasional X-Y recombination in all species where LG1 is sex linked. These patterns argue against one of the main potential causes for turnovers, namely the accumulation of deleteriousmutations on nonrecombining chromosomes. Sibship analyses show that LG1 recombination is strongly reduced in males from most species investigated, including some in which it is autosomal. Intrinsically low male recombination might facilitate the evolution of male heterogamety, and the presence of important genes from the sex-determination cascade might predispose LG1 to become a sex chromosome.</P>
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