The Ap-Bp blood groups of baboons

Four isoimmunized baboons each produced isoantibodies defining a number of blood factors of baboon blood of which two, A^p and B^p, have been most intensively studied. The two blood factors determine the A^P-B^P blood group system which, judging from its serological behavior, may be the baboon analogue of the human M-N system and the chimpanzee V-A-B system. Tests for A^P-B^P types of 592 baboons showed striking differences in the distributions of the four types among the four sub-species, Papio cynocephalus, Papio anubis, Papio ursinus (South Africa) and Papio papio (Senegal). The baboon A^P-B^P types could also be demonstrated by tests on the red cells of geladas (Theropithecus gelada). If one assumes inheritance by multiple allelic genes, then the existence of only a single gene O^p need be invoked for Papio ursinus, three alleles O^p, A^p and B^p for Papio cynocephalus and Papio anubis, but four alleles for Papio papio including an allele, very frequent in that subspecies, which determines an agglutinogen having both blood factors A^p and B^p.     

An unstable gene controlling developmental variegation in okra (Abelmoschus esculentus (L.) Moench)

Summary Genetic studies on radiation-induced chlorina and variegated mutants of okra (Abelmoschus esculentus (L.) Moench) revealed the existence of an unstable gene. The normal green color of the leaves is controlled by duplicate genes C₁ and C₂, either of which produces the green colour. The chlorina plants are C ₁ C ₁ C ₂ C ₂. The allele c ₁ ^v is dominant to both C ₁ and C ₂ but is unstable. The homozygote c ₁ ^v c ₁ ^v c ₂ c ₂ is a normal green while the heterozygote c _i ^v c ₁ c ₂ c ₂ has a variegated phenotype as a result of the mutation of c ₁ ^v to c ₁ during development. In green plants with a c ₁ ^v c{sh1/v}c ₂ c ₂ genotype, the autonomous mutation of one of the c ₁ ^v alleles to c ₁ may take place at the pre-meiotic stage. In the variegated genotype (c ₁ ^v c ₁ c ₂ c ₂), the mutation of c ₁ to c ₁ ^v may take place in early ontogeny, thus producing green plants. The allele C ₁, when associated with c ₁ ^v in a heterozygous condition, mutates to c ₁ at the pre-meiotic stage even in the presence of the allele C ₂.     

Blood groups of anthropoid apes and their relationship to human blood groups

Affinity between blood groups of man and those of anthropoid apes is reflected not only in similarities or identities of reactions of the red cells with many specific typing reagents, but also in overall structures of some of the main blood group systems defined in man and in apes.Besides specificities of human-type, such as A-B-O, M-N, Rh-Hr, I-i, etc. known to be present on the red cells of various species of apes, specific reagents were produced by iso- or cross-immunization of chimpanzees that detect red cell specificities characteristic for apes only. Some of those specificities were found to be shared by several ape species and to fall into separate blood group systems that are counterparts of the human blood group systems. Recently obtained serological, as well as population data, indicate that the chimpanzee R-C-E-F blood group system is the counterpart of the human Rh-Hr system. Similarly to the Rh-Hr system, it is built around a main antigen, the R^c antigen, to which secondary specificities are attached by means of multiple allelic genes. The R^c is not only the principal factor of the chimpanzee R-C-E-F group system, but also constitutes a direct link with the human Rh-Hr blood group system, since anti-R^c reagents also detect Rh₀ specificity on the human red cells. Another chimpanzee blood group system, the V-A-B-D system, is counterpart of the M-N-S-s system, and is built around the central antigen V^c. the V^c is not only the principal specificity of the chimpanzee V-A-B-D system, but it also constitutes the direct link with the human M-N-S-s system since anti-V^c reagent gives with chimpanzee red cells reactions parralleling those obtained with anti-N lectin (N^v) while in tests with human red cells it detects specificity identical or closely related to the Mi^a specificity.     

Trans-species origin of Mhc-DRB polymorphism in the chimpanzee

Trans-specific evolution of allelic polymorphism at the major histocompatibility complex loci has been demonstrated in a number of species. Estimating the substitution rates and the age of trans-specifically evolving alleles requires detailed information about the alleles in related species. We provide such information for the chimpanzee DRB genes. DNA fragments encompassing exon 2 were amplified in vitro from genomic DNA of ten chimpanzees. The nucleotide sequences were determined and their relationship to the human DRB alleles was evaluated. The alleles were classified according to their positioni in dendrograms and the presence of lineage-specific motifs. Twenty alleles were found at the expressed loci Patr-DRB1,-DRB3, -DRB4, -DRB5, and at the pseudogenes Patr-DRB6, -DRB7; of these, 13 are new alleles. Two other chimpanzee sequences were classified as members of a new lineage tentatively designated DRBX. Chimpanzee counterparts of HLA-DRB1 ^* 01 and ^* 04 were not detected. The number of alleles found at individual loci indicates asymmetrical distribution of polymorphism between humans and chimpanzees. Estimations of intra-lineage divergence times suggest that the lineages are more than 30 million year old. Predictions of major chimpanzee DRB haplotypes are made.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers M94937-M94954.     

Caprine blood groups. 2. The C,G, H,I, J,K, L,N, and Q systems

Nine blood group systems of goats were identified using 12 caprine reagents produced by absorption of alloimmune antisera. The caprine C blood group system, possibly homologous to the ovine C blood group system, was characterized by two reagents and shown to be controlled by three alleles,C ¹²,C ²⁵, andC ⁻. A more complex blood group system of goats, designated G, was identified using three reagents and shown to be controlled by six codominant alleles (G ^10.19.20,G ^10.19,G ^10.20,G ¹⁰,G ¹⁹,G ²⁰) and a recessive allele (G ⁻). A further seven one-factor two-allelic systems were identified by seven reagents. The nine genetic systems provided exclusion probabilities of 0.479, 0.492, 0.548, and 0.572 in Australian Angora, Dairy, Cashmere, and Texan Angora goat breeds, respectively. This work was supported by a grant from the Australian Stud Book, Alison Road, Randwick, New South Wales 2031, Australia.     

Common chimpanzees have greater diversity than humans at two of the three highly polymorphic MHC class I genes

 MHC class I polymorphism improves the defense of vertebrate species against viruses and other intracellular pathogens. To see how polymorphism at the same class I genes can evolve in different species we compared the MHC-A, MHC-B, and MHC-C loci of common chimpanzees and humans. Diversity in 23 Patr-A, 32 Patr-B, and 18 Patr-C alleles obtained from study of 48 chimpanzees was compared to diversity in 66 HLA-A, 149 HLA-B, and 41 HLA-C alleles obtained from a study of over 1 million humans. At each locus, alleles group hierarchically into families and then lineages. No alleles or families are shared by the two species, commonality being seen only at the lineage level. The overall nucleotide sequence diversity of MHC class I is estimated to be greater for modern chimpanzees than humans. Considering the numbers of lineages, families, and alleles, Patr-B and Patr-C have greater diversity than the HLA-B and HLA-C, respectively. In contrast, Patr-A has less polymorphism than HLA-A, due to the absence of A2 lineage alleles. The results are consistent with ancestral humans having passed through a narrower population bottleneck than chimpanzees, and with pathogen-mediated selection having favored either preservation of A2 lineage alleles on the human line and/or their extinction on the chimpanzee line. Received: 8 December 1999 / Accepted: 30 December 1999     

PHOTOSYNTHESIS AND COLD ACCLIMATION: MOLECULAR EVIDENCE FROM A POLAR DIATOM1

The psychrophilic diatom Fragilariopsis cylindrus (Grunow) Krieger in Helmcke & Krieger was used to investigate photosynthesis and growth under freezing temperatures. Gene expression during a temperature shift from +5° C to ?1.8° C was studied under 3 and 35 μmol photons·m^?2·s^?1 by using a macroarray. These measurements were paralleled by determination of fluorescence induction at PSII and pigment analysis. The shift to ?1.8° C at 35 μmol photons·m^?2·s^?1 caused a marginal decrease of photosynthetic quantum yield (F_v/F_m) from 0.61 to 0.52 with fast recovery after 1 day. The ratio of chl c to chl a increased from 3.1 to 5.5, and the ratio of diatoxanthin to diadinoxanthin increased from 0.7 to 5.0. Genes encoding proteins of PSII (psbA, psbC) and for carbon fixation (rbcL) were down‐regulated, whereas genes encoding chaperons (hsp70) and genes for plastid protein synthesis and turnover (elongation factor EfTs, ribosomal protein rpS4, ftsH protease) were up‐regulated. In contrast, cold exposure at 3 μmol photons·m^?2·s^?1 induced a marginal increase in F_v/F_m from 0.61 to 0.63 and a strong increase in fucoxanthin concentrations from 0.04 up to 0.12 pg·cell^?1. This was paralleled by up‐regulation of fcp genes. The ratio of chl c to chl a also increased from 3.1 to 4.2, as did the ratio of diatoxanthin to diadinoxanthin from 0.7 to 2.2. Down‐regulation of psbA, psbC, and rbcL could also be measured but not up‐regulation of hsp70, EfTs, rpS4, and the ftsH protease. The latter genes are probably necessary to avoid cold shock photoinhibition only at higher light intensities.     

Distribution of transferrin phenotypes in selected troops of Kenya baboons

The distribution of transferrin alleles in a group of common baboons, Papio cynocephalus of East Africa, was determined after starch gel electrophoresis of plasma and autoradiography of electrophoretograms. Three alleles, Tf^A, Tf^B, and Tf^C, were found, in agreement with results previously reported. The frequencies of these alleles are Tf^A = 0.276, Tf^B = 0.515, Tf^c = 0.209. The difference between the frequencies reported here and those reported by Buettner-Janusch (1963 Folia Primat., 1: 73–87) for the same species (Tf^A = 0.205, Tf^B = 0.332, Tf^c = 0.463) is significant. Transferrin of P. cynocephalus contains four residues of sialic acid per molecule of transferrin, as determined by electrophoresis and autoradiography of plasma treated with neuraminidase.     

A human-specific allelic group of the MHC DRB1 gene in primates

Background

Diversity among human leukocyte antigen (HLA) molecules has been maintained by host-pathogen coevolution over a long period of time. Reflecting this diversity, the HLA loci are the most polymorphic in the human genome. One characteristic of HLA diversity is long-term persistence of allelic lineages, which causes trans-species polymorphisms to be shared among closely related species. Modern humans have disseminated across the world after their exodus from Africa, while chimpanzees have remained in Africa since the speciation event between humans and chimpanzees. It is thought that modern humans have recently acquired resistance to novel pathogens outside Africa. In the present study, we investigated HLA alleles that could contribute to this local adaptation in humans and also studied the contribution of natural selection to human evolution by using molecular data.

Results

Phylogenetic analysis of HLA-DRB1 genes identified two major groups, HLA Groups A and B. Group A formed a monophyletic clade distinct from DRB1 alleles in other Catarrhini, suggesting that Group A is a human-specific allelic group. Our estimates of divergence time suggested that seven HLA-DRB1 Group A allelic lineages in humans have been maintained since before the speciation event between humans and chimpanzees, while chimpanzees possess only one DRB1 allelic lineage (Patr-DRB1*03), which is a sister group to Group A. Experimental data showed that some Group A alleles bound to peptides derived from human-specific pathogens. Of the Group A alleles, three exist at high frequencies in several local populations outside Africa.

Conclusions

HLA Group A alleles are likely to have been retained in human lineages for a long period of time and have not expanded since the divergence of humans and chimpanzees. On the other hand, most orthologs of HLA Group A alleles may have been lost in the chimpanzee due to differences in selective pressures. The presence of alleles with high frequency outside of Africa suggests these HLA molecules result from the local adaptations of humans. Our study helps elucidate the mechanism by which the human adaptive immune system has coevolved with pathogens over a long period of time.     

A new ENU-induced allele of mouse quaking causes severe CNS dysmyelination

The mutant allelic series of the mouse quaking gene consists of the spontaneous quaking^viable (qk^v) allele, which is homozygous viable with a dysmyelination phenotype, and four ENU-induced alleles (qk^kt1, qk^k2, qk^kt3/4, and qk^l-1), which are homozygous embryonic lethal. Here we report the isolation of qk^e5, the first ENU-induced viable allele of quaking. Unlike qk^v/qk^v, qk^e5/qk^e5 animals have early-onset seizures, severe ataxia, and a dramatically reduced lifespan. Ultrastructural analysis of qk^e5/qk^e5 brains reveals severe dysmyelination when compared with both wild-type and qk^v/qk^v brains. In addition, Calbindin detection in young adult qk^e5/qk^e5 mice reveals Purkinje cell axonal swellings indicative of neurodegeneration , which is not seen in young adult qk^v/qk^v mice. Although the molecular defect in the qk^e5 allele is not evident by sequencing, protein expression studies show that qk^e5/qk^e5 postnatal oligodendrocytes lack the QKI-6 and QKI-7 isoforms and have reduced QKI-5 levels. The oligodendrocyte developmental markers PDGFαR, NG2, O4, CNP, and MBP are also present in the qk^e5/qk^e5 postnatal brain although CNP and MBP levels are considerably reduced. Because the qk^v allele is a large deletion that affects the expression of three genes, the new neurologic qk^e5 allele is an important addition to this allelic series.     

Novel DNA variations to characterize low molecular weight glutenin Glu-D3 genes and develop STS markers in common wheat

Low-molecular-weight glutenin subunits (LMW-GS) play an important role in bread and noodle processing quality by influencing the viscoelasticity and extensibility of dough. The objectives of this study were to characterize Glu-D3 subunit coding genes and to develop molecular markers for identifying Glu-D3 gene haplotypes. Gene specific primer sets were designed to amplify eight wheat cultivars containing Glu-D3a, b, c, d and e alleles, defined traditionally by protein electrophoretic mobility. Three novel Glu-D3 DNA sequences, designated as GluD3-4, GluD3-5 and GluD3-6, were amplified from the eight wheat cultivars. GluD3-4 showed three allelic variants or haplotypes at the DNA level in the eight cultivars, which were designated as GluD3-41, GluD3-42 and GluD3-43. Compared with GluD3-42, a single nucleotide polymorphism (SNP) was detected for GluD3-43 in the coding region, resulting in a pseudo-gene with a nonsense mutation at the 119th position of deduced peptide, and a 3-bp insertion was found in the coding region of GluD3-41, leading to a glutamine insertion at the 249th position of its deduced protein. The coding regions for GluD3-5 and GluD3-6 showed no allelic variation in the eight cultivars tested, indicating that they were relatively conservative in common wheat. Based on the 12 allelic variants of three Glu-D3 genes identified in this study and three detected previously, seven STS markers were established to amplify the corresponding gene sequences in wheat cultivars containing five Glu-D3 alleles (a, b, c, d and e). The seven primer sets M2F12/M2R12, M2F2/M2R2, M2F3/M2R3, M3F1/M3R1, M3F2/M3R2, M4F1/M4R1 and M4F3/M4R3 were specific to the allelic variants GluD3-21/22, GluD3-22, GluD3-23, GluD3-31, GluD3-32, GluD3-41 and GluD3-43, respectively, which were validated by amplifying 20 Chinese wheat cultivars containing alleles a, b, c and f based on protein electrophoretic mobility. These markers will be useful to identify the Glu-D3 gene haplotypes in wheat breeding programs. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Reconstituting the genome of a young allopolyploid crop,Brassica napus,with its related species

Brassica napus (AⁿAⁿCⁿCⁿ) is an important worldwide oilseed crop, but it is a young allotetraploid with a short evolutionary history and limited genetic diversity. To significantly broaden its genetic diversity and create a novel heterotic population for sustainable rapeseed breeding, this study reconstituted the genome of B. napus by replacing it with the subgenomes from 122 accessions of Brassica rapa (A^rA^r) and 74 accessions of Brassica carinata (B^cB^cC^cC^c) and developing a novel gene pool of B. napus through five rounds of extensive recurrent selection. When compared with traditional B. napus using SSR markers and high‐throughput SNP/Indel markers through genotyping by sequencing, the newly developed gene pool and its homozygous progenies exhibited a large genetic distance, rich allelic diversity, new alleles and exotic allelic introgression across all 19 AC chromosomes. In addition to the abundant genomic variation detected in the AC genome, we also detected considerable introgression from the eight chromosomes of the B genome. Extensive trait variation and some genetic improvements were present from the early recurrent selection to later generations. This novel gene pool produced equally rich phenotypic variation and should be valuable for rapeseed genetic improvement. By reconstituting the genome of B. napus by introducing subgenomic variation within and between the related species using intense selection and recombination, the whole genome could be substantially reorganized. These results serve as an example of the manipulation of the genome of a young allopolyploid and provide insights into its rapid genome evolution affected by interspecific and intraspecific crosses.     

Mutator activity in uvs mutants of Aspergillus nidulans

Summary The frequency of selenate-resistant spontaneous mutants was determined among the conidia of two uvs ⁺, two allelic uvsB, one uvsD, three allelic uvsC and three allelic uvsE strains of Aspergillus nidulans. In the uvsB, uvsD, uvsC and uvsE mutants the median frequencies of mutation were respectively 1.7, 1.8, 8.7 and 4.0 times as high as in the uvs ⁺ strains. The selenate resistance resulted from mutation at the chromosomal loci sB or sC. It is concluded that the uvs alleles enhance spontaneous mutation in chromosomal genes.     

Variability and genetics of spacer DNA sequences between the ribosomal-RNA genes of hexaploid wheat (Triticum aestivum)

Summary Using restriction enzyme digests of genomic DNA extracted from the leaves of 25 hexaploid wheat (Triticum aestivum L. em. Thell.) cultivars and their hybrids, restriction fragment length polymorphisms of the spacer DNA which separates the ribosomal-RNA genes have been examined. (From one to three thousand of these genes are borne on chromosomes 1B and 6B of hexaploid wheat). The data show that there are three distinct alleles of the 1B locus, designated Nor-B1a, Nor-B1b, and Nor-B1c, and at least five allelic variants of the 6B locus, designated Nor-B2a, Nor-B2b, Nor-B2c, Nor-B2d, and Nor-B2e. A further, previously reported allele on 6B has been named Nor-B2f. Chromosome 5D has only one allelic variant, Nor-D3. Whereas the major spacer variants of the 1B alleles apparently differ by the loss or gain of one or two of the 133 bp sub-repeat units within the spacer DNA, the 6B allelic variants show major differences in their compositions and lengths. This may be related to the greater number of rDNA repeat units at this locus. The practical implications of these differences and their application to wheat breeding are discussed.     

Genetics of esterase isoenzymes in Malus

Summary Three main zones of esterase activity (EST-I, EST-III, EST-IV) identified in leaf extracts of cultivated apple and Malus species were determined by the genes EST-1, EST-3 and EST-4, respectively. In addition to earlier reported alleles of EST-1 (a, b) three further bands c, d and f were identified in the EST-I zone of which c was found to be determined by an allele, c. Two alleles, a, b, and a null allele were found for both the genes EST-3 and EST-4. Differences in allelic frequency were observed between cultivars, rootstocks and Malus species. Allele EST-1a was rare amongst the rootstocks. The examination of Malus species and derivatives showed a geographical relationship. Allele EST-1c was confined to species of Asian origin, and EST-1d was confined to American species.     

Phylogenetic Relationships and Intraspecific Variation of D-Genome Aegilops L. as Revealed by RAPD Analysis

RAPD analysis was carried out to study the genetic variation and phylogenetic relationships of polyploid Aegilops species, which contain the D genome as a component of the alloploid genome, and diploid Aegilops tauschii, which is a putative donor of the D genome for common wheat. In total, 74 accessions of six D-genome Aegilops species were examined. The highest intraspecific variation (0.03–0.21) was observed for Ae. tauschii. Intraspecific distances between accessions ranged 0.007–0.067 in Ae. cylindrica, 0.017–0.047 in Ae. vavilovii, and 0–0.053 inAe. juvenalis.Likewise, Ae. ventricosaand Ae. crassa showed low intraspecific polymorphism. The among-accession difference in alloploidAe. ventricosa (genome D^vN^v) was similar to that of one parental species, Ae. uniaristata (N), and substantially lower than in the other parent, Ae. tauschii (D). The among-accession difference in Ae. cylindrica(C^cD^c) was considerably lower than in either parent, Ae. tauschii (D) orAe. caudata (C). With the exception of Ae. cylindrica, all D-genome species—Ae. tauschii (D),Ae. ventricosa (D^vN^v), Ae. crassa (X^crD^cr1 and X^crD^cr1D^cr2), Ae. juvenalis (X^jD^jU^j), andAe. vavilovii (X^vaD^vaS^va)—formed a single polymorphic cluster, which was distinct from clusters of other species. The only exception, Ae. cylindrica(C^cD^c), did not group with the other D-genome species, but clustered withAe. caudata (C), a donor of the C genome. The cluster of these two species was clearly distinct from the cluster of the other D-genome species and close to a cluster of Ae. umbellulata (genome U) and Ae. ovata (genome U^gM^g). Thus, RAPD analysis for the first time was used to estimate and to compare the interpopulation polymorphism and to establish the phylogenetic relationships of all diploid and alloploid D-genome Aegilops species.     

A phylogenetic analysis of cattle DRB3 alleles with a deletion of codon 65

 One of the most common cattle major histocompatibility complex DRB3 alleles, ^* 0201, includes a deletion of codon 65 encoding one residue in the α-helical chain. The mutation is functionally interesting and is likely to influence peptide binding. Exon 2 of two additional del65 alleles, ^* 3301 and ^* 4101, have now been sequenced with the aim to investigate the evolutionary relationship of this allelic group. Despite a fairly large genetic distance between the three alleles (11–17 nucleotide substitutions causing 8–11 amino acid substitutions) we found clear indications of a common ancestry. The α-helical region was very similar or identical among the alleles whereas the β-strand region was quite divergent. The results indicated that interallelic recombination has contributed to the diversification of the del65 group. Deletion of codon 65 has also been found in a roe deer DRB1 allele and a cattle DQB3 allele. Sequence comparisons of the cattle and roe deer DRB del65 alleles refuted the possibility of a trans-species persistence of a del65 allelic lineage but the two species may share a short ancestral sequence motif including del65. In addition to del65, the cattle DQB3 allele did not show any striking sequence similarities to the DRB alleles. Received: 20 March 1997 / Revised: 17 June 1997     

Genotypic effects on the frequency of homoeologous and homologous recombination in <Emphasis Type="Italic">Brassica napus</Emphasis> × <Emphasis Type="Italic">B. carinata</Emphasis> hybrids

We investigated the influence of genotype on homoeologous and homologous recombination frequency in eight different Brassica napus (AACⁿCⁿ) × B. carinata (BBC^cC^c) interspecific hybrids (genome composition CⁿC^cAB). Meiotic recombination events were assessed through microsatellite marker analysis of 67 unreduced microspore-derived progeny. Thirty-four microsatellite markers amplified 83 A-, B-, Cⁿ- and C^c-genome alleles at 64 loci, of which a subset of seven markers amplifying 26 alleles could be used to determine allele copy number. Hybrid genotypes varied significantly in loss of A- and B-genome alleles (P < 0.0001), which ranged from 6 to 22% between hybrid progeny sets. Allele copy number analysis revealed 19 A–C, 3 A–B and 10 B–C duplication/deletion events attributed to homoeologous recombination. Additionally, 55 deletions and 19 duplications without an accompanying dosage change in homoeologous alleles were detected. Hybrid progeny sets varied in observed frequencies of loss, gain and exchange of alleles across the A and B genomes as well as in the diploid C genome. Self-fertility in hybrid progeny decreased as the loss of B-genome loci (but not A-genome loci) increased. Hybrid genotypes with high levels of homologous and homoeologous exchange may be exploited for genetic introgressions between B. carinata and B. napus (canola), and those with low levels may be used to develop stable synthetic Brassica allopolyploids.     

The role of major histocompatibility complex diversity in vigour of fish males (Abramis brama L.) and parasite selection

The major histocompatibility complex (MHC) presents a group of genes with highly polymorphic loci involved in specific immune responses. The factors maintaining extensive MHC polymorphism have been questioned, considering three possible hypotheses of parasite‐mediated selection driving an extensive MHC diversity (i.e. heterozygote advantage, rare‐allele advantage, and favouring optimal MHC diversity). The patterns of MHC diversity of class IIB genes were investigated following two noncontradicting hypotheses, parasite‐driven selection and MHC‐based mating preferences, using males of common bream collected in the spawning period. Two allelic groups DAB1 and DAB3 were recognized from the phylogenetic analyses. Individuals expressed one or two alleles of the same or different allelic groups. Several individuals shared identical alleles; however, the presence of parasite species was not associated with the occurrence of a particular allele. The presence of different allelic groups (only DAB1, only DAB3, or both DAB1 and DAB3) in individuals was not associated with parasite presence or diversity. The expression of two DAB1 alleles was associated with higher endoparasite abundance. Moreover, nucleotide diversity in individuals expressing a single type of alleles (DAB1 or DAB3) increased with the abundance of ectoparasitic Dactylogyrus spp. (Monogenea) and Ergasilus sp. (Crustacea). This suggests that the expression of two alleles of a single allelic type is related to high metazoan parasite infection whereas no significant influence of parasitism on the combined allelic form (the presence of both DAB1 and DAB3 alleles) was found. Moreover, the expression of two alleles of a single allelic type was related to decreased immunocompetence measured by spleen size. The condition factor was higher in fish expressing the combined allelic type. Thus, the presence of alleles of different lineages in individuals appears to be advantageous for individual male fitness. The expression of a single allelic type was related to higher sexual ornamentation, which could support the role of MHC in the hypothesis of the sexual selection of ‘good genes’. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90 , 525–538.