Major histocompatibility complex heterozygote advantage and widespread bacterial infections in populations of Chinook salmon (<i>Oncorhynchus tshawytscha</i>)

Evans, Melissa L.; Neff, Bryan D.

doi:10.1111/j.1365-294x.2009.04374.x

Cited by 95 publications

(115 citation statements)

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“…For example, pathogen invasion must be prevented in all species. This has been observed in the study of MHC II molecular evolution (Surridge et al, 2008;Evans and Neff, 2009). …”

Section: Conservation Of Mdii-2 Indicates the Same Function And Similsupporting

confidence: 52%

Molecular characterization and tissue-specific expression of invariant chain isoform in Muscovy Duck (Cairina moschata)

Liu¹,

Chen²,

Wu³

et al. 2014

Genet. Mol. Res.

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ABSTRACT. Invariant chain (Ii) isoform, through its thyroglobulin-like (Tg) domain, inhibits cysteine proteases during antigen presentation in vertebrates. In birds, the Ii of Muscovy Duck (MDIi) has 2 forms: MDIi-1 and MDIi-2 (MDIi isoform). To understand the genetic information and expression characteristics of MDIi-2, polymerase chain reaction, and bioinformatic analysis were performed for MDIi-2 from healthy adult Muscovy Duck. The full-length MDIi-2 cDNA sequence was found to be 1377-base pairs, encoding a 285-amino acid protein. MDIi-2 contains 63 amino acids with an insertion sequence in the Tg domain. MDIi-2 shares high identity (72.51-94.74%) with the same protein in other birds. The Tg domain of MDIi-2 is highly conserved and showed relatively high identity (96.83%) among all tested birds. The molecular structure of the Tg domain supports this conservation. MDIi-2 expression was measured in various tissues using real-time quantitative polymerase chain reaction. Similar to MDIi-1, MDIi-2 was detected in all tissues but at different levels. Higher expression level was observed in the spleen, intestinal mucosa, and bursa stipe (bursa of Fabricius stipe) than in other tissues. This suggests that MDIi-2, like MDIi-1, plays an essential role in all tissues and that its differential expression may be related to its functions in these tissues. The coexistence of 2 MDIi isoforms indicates that their functions are correlated in Muscovy Duck. This study improves the understanding of poultry immunology and may be used to improve measures to protect Muscovy Duck from disease.

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“…For example, pathogen invasion must be prevented in all species. This has been observed in the study of MHC II molecular evolution (Surridge et al, 2008;Evans and Neff, 2009). …”

Section: Conservation Of Mdii-2 Indicates the Same Function And Similsupporting

confidence: 52%

Molecular characterization and tissue-specific expression of invariant chain isoform in Muscovy Duck (Cairina moschata)

Liu¹,

Chen²,

Wu³

et al. 2014

Genet. Mol. Res.

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“…Other studies of the MHC have also found higher levels of observed heterozygosity than expected, suggesting that selection for heterozygotes is occurring in many species (for example, Seddon and Baverstock, 1999;van Haeringen et al, 1999;Peters and Turner, 2008;Oliver et al, 2009;see Garrigan and Hedrick, 2003 for review). In a recent study, we have shown that MHC class II heterozygous Chinook salmon fry exhibit fewer bacterial infections that do homozygotes (Evans and Neff, 2009). Moreover, a study by Arkush et al (2002) on Chinook salmon showed that heterozygotes at the MHC class II exhibited higher survival than homozygotes when challenged with infectious haematopoietic necrosis virus (but see Langefors et al, 2001).…”

Section: Evans Et Almentioning

confidence: 95%

MHC genetic structure and divergence across populations of Chinook salmon (Oncorhynchus tshawytscha)

2009

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The major histocompatibility complex (MHC) is thought to be under strong selection pressure because of its integral role in pathogen recognition. Consequently, patterns of MHC genetic variation should reflect selection pressures across the landscape. We examined genetic variation and population genetic structure at the MHC class I-A1 and class II-B1 exons in five Chinook salmon (Oncorhynchus tshawytscha) populations from two geographic regions in British Columbia, Canada. We then compared estimates of population structure at the MHC genes with neutral estimates based on microsatellites to examine the potential for local adaptation at the MHC. Chinook salmon are in decline throughout much of their native range and understanding the degree of local adaptation exhibited by the MHC may be important in conservation planning. Comparisons among populations yielded higher G 0 ST estimates for the MHC class I than expected under neutrality based on the microsatellites. In contrast, the MHC class II tended to exhibit lower G 0 ST values than did the microsatellites. These results suggest that across populations unique selection pressures are driving allele frequency differences at the MHC class I but that the MHC class II may be the subject of homogenizing selection. Rates of nonsynonymous versus synonymous substitutions found in codons associated within the MHC class I and II peptide-binding regions provided strong evidence of positive selection. Together, these results support the hypothesis that selection is influencing genetic variation at the MHC, but suggest that selection pressures may vary at the two classes of loci both at the sequence and population levels.

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“…Hence, putative LA at MHC loci can be viewed as a hierarchical process with different dynamics acting on different geographical scales. Yet a similar study on chinook salmon (Oncorhynchus tshawytscha) found no evidence for any MHC alleles to confer bacterial resistance (Evans and Neff 2009). Further research is merited to discern complexities related to the role of pathogen communities in the evolution of salmonid host LA.…”

Section: Approach IImentioning

confidence: 99%

Extent and scale of local adaptation in salmonid fishes: review and meta-analysis

et al. 2011

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What is the extent and scale of local adaptation (LA)? How quickly does LA arise? And what is its underlying molecular basis? Our review and meta-analysis on salmonid fishes estimates the frequency of LA to be B55-70%, with local populations having a 1.2 times average fitness advantage relative to foreign populations or to their performance in new environments. Salmonid LA is evident at a variety of spatial scales (for example, few km to41000 km) and can manifest itself quickly (6-30 generations). As the geographic scale between populations increases, LA is generally more frequent and stronger. Yet the extent of LA in salmonids does not appear to differ from that in other assessed taxa. Moreover, the frequency with which foreign salmonid populations outperform local populations (B23-35%) suggests that drift, gene flow and plasticity often limit or mediate LA. The relatively few studies based on candidate gene and genomewide analyses have identified footprints of selection at both small and large geographical scales, likely reflecting the specific functional properties of loci and the associated selection regimes (for example, local niche partitioning, pathogens, parasites, photoperiodicity and seasonal timing). The molecular basis of LA in salmonids is still largely unknown, but differential expression at the same few genes is implicated in the convergent evolution of certain phenotypes. Collectively, future research will benefit from an integration of classical and molecular approaches to understand: (i) species differences and how they originate, (ii) variation in adaptation across scales, life stages, population sizes and environmental gradients, and (iii) evolutionary responses to human activities.

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Major histocompatibility complex heterozygote advantage and widespread bacterial infections in populations of Chinook salmon (Oncorhynchus tshawytscha)

Cited by 95 publications

References 72 publications

Molecular characterization and tissue-specific expression of invariant chain isoform in Muscovy Duck (Cairina moschata)

Molecular characterization and tissue-specific expression of invariant chain isoform in Muscovy Duck (Cairina moschata)

MHC genetic structure and divergence across populations of Chinook salmon (Oncorhynchus tshawytscha)

Extent and scale of local adaptation in salmonid fishes: review and meta-analysis

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