Major histocompatibility complex class IIB allele polymorphism and its association with resistance/susceptibility to Vibrio anguillarum in Japanese flounder (Paralichthys olivaceus).

摘要

The full length of major histocompatibility complex (MHC) class IIB cDNA was cloned from a Chinese population of Japanese flounders (Paralichthys olivaceus) by homology cloning and rapid amplification of cDNA ends-PCR (RACE-PCR). The MHC IIB genomic sequence is 1864 bp long and consists of 34-bp 5'UTR, 741-bp open reading frame, 407-bp 3'UTR, 96-bp intron 1, 392-bp intron 2, 85-bp intron 3 and 109-bp intron 4. Phylogenetic analysis showed that the putative MHC class IIB amino acid of the fish shared 28.3 to 85.4% identity with that of the reported MHC class IIB in other species. A significant association between MHC IIB polymorphism and disease resistance/susceptibility was found in the flounders. 13 different MHC IIB alleles were identified among 411 clones from 84 individuals. Among the 280 (268) nucleotides, 32 (11.4%) nucleotide positions were variable. Most alleles such as alleles a, b, c, d, e, f, j, k, i, m were commonly found in both resistant and susceptible stock. Via phi2 test, allele d was significantly more prevalent in individuals from susceptible stock than from resistant stock and their percentages were 23.80 and 7.14%, respectively. In addition, allele g occurred in 9 and allele h in 4 of 42 resistant individuals that were not present in the susceptible stock; their percentages were 21.4 and 9.52%, respectively. Although allele l was found only in 8 individuals from the susceptible stock, its percentage was 19.05%.