Association between major histocompatibility complex class IIB alleles and resistance to Aeromonas salmonicida in Atlantic salmon
Association between major histocompatibility complex class IIB alleles and resistance to Aeromonas salmonicida in Atlantic salmon
复制标题
DOI：
10.1098/rspb.2000.1378
复制
发表时间：
2001-03-07
影响因子：
4.7
通讯作者：
von Schantz, T
中科院分区：
文献类型：
--
作者：
Langefors, Å;Lohm, J;von Schantz, T
我们测试了大西洋鲑鱼(Salmo Salar)主要组织相容性复合体(MHC)IIB类基因变异对在受到高毒力细菌病原体攻击后存活的重要性。来自120个家庭的40个幼鱼全同胞感染了沙门氏气单胞菌，这种细菌导致鲑鱼因腐殖病而高死亡率。采用变性梯度凝胶电泳法(DGGE)对高抗(HR，<；35%死亡率)和低抗(LR，&Gt；80%死亡率)家系鱼类进行MHC-IIB基因分型。编码多肽结合区主要部分的外显子2序列是在每个DGGE片段上建立的。一个含有错义单碱基替换的等位基因e在HR家系中显著高于LR家系。一项赔率测试表明，携带该等位基因的后代患高血压的几率是没有该等位基因的后代的12倍。第二个等位基因I在未感染和存活的个体中的频率明显高于感染死亡的个体。第三个等位基因j倾向于在LR家庭和死于感染的个人中更普遍。MHC杂合性与对沙门氏菌的抗性无相关性。我们的结果支持这样的假设，即MHC多态是通过病原体驱动的选择来维持的，这种选择是通过频率依赖的选择而不是杂合优势来实现的。
We have tested the importance of genetic variation in the major histocompatibility complex (MHC) class IIB in Atlantic salmon (Salmo salar) for survival after challenge with a highly virulent bacterial pathogen. Forty juvenile full siblings from each of 120 families were infected with the bacterium Aeromonas salmonicida, which causes high mortality in salmon due to furunculosis. Fishes from high-resistance (HR, < 35% mortality) and low-resistance (LR, > 80% mortality) families were screened for their MHC class IIB genotypes using the denaturing gradient gel electrophoresis (DGGE) technique. The exon 2 sequences, encoding the major part of the peptide-binding region, were established far each DGGE fragment. One allele, e, containing a missense single base substitution was significantly more prevalent in HR families than in LR families. An odds-ratio test showed that broods carrying this allele had a 12-fold higher chance of being HR than broods without the e allele. A second allele, i, showed significantly higher frequencies in uninfected and surviving individuals than in infected dead individuals. A third allele, j, tended to be more prevalent both in LR families and in individuals that had died of the infection. There was no correlation between MHC heterozygosity and resistance to A. salmonicida. Our results support the hypothesis that MHC polymorphism is maintained through pathogen-driven selection acting by means of frequency-dependent selection rather than heterozygous advantage.