Unusually High Recombination Rate Detected in the Sex Locus Region of the Honey Bee (Apis mellifera)

Abstract Sex determination in Hymenoptera is controlled by haplo-diploidy in which unfertilized eggs develop into fertile haploid males. A single sex determination locus with several complementary alleles was proposed for Hymenoptera [so-called complementary sex determination (CSD)]. Heterozygotes at the sex determination locus are normal, fertile females, whereas diploid zygotes that are homozygous develop into sterile males. This results in a strong heterozygote advantage, and the sex locus exhibits extreme polymorphism maintained by overdominant selection. We characterized the sex-determining region by genetic linkage and physical mapping analyses. Detailed linkage and physical mapping studies showed that the recombination rate is <44 kb/cM in the sex-determining region. Comparing genetic map distance along the linkage group III in three crosses revealed a large marker gap in the sex-determining region, suggesting that the recombination rate is high. We suggest that a “hotspot” for recombination has resulted here because of selection for combining favorable genotypes, and perhaps as a result of selection against deleterious mutations. The mapping data, based on long-range restriction mapping, suggest that the Q DNA-marker is within 20,000 bp of the sex locus, which should accelerate molecular analyses.

Download Full-text

Complementary sex determination, inbreeding depression and inbreeding avoidance in a gregarious sawfly

Heredity ◽

10.1038/hdy.2016.46 ◽

2016 ◽

Vol 117 (5) ◽

pp. 326-335 ◽

Cited By ~ 15

Author(s):

K E Harper ◽

R K Bagley ◽

K L Thompson ◽

C R Linnen

Keyword(s):

Sex Determination ◽

Inbreeding Depression ◽

Inbreeding Avoidance ◽

Complementary Sex Determination

Download Full-text

Linkage Analysis of Sex Determination in Bracon sp. Near hebetor (Hymenoptera: Braconidae)

Genetics ◽

10.1093/genetics/154.1.205 ◽

2000 ◽

Vol 154 (1) ◽

pp. 205-212

Author(s):

Alisha K Holloway ◽

Michael R Strand ◽

William C Black ◽

Michael F Antolin

Keyword(s):

Linkage Group ◽

Sex Determination ◽

Rapd Markers ◽

Random Amplified Polymorphic Dna ◽

Parasitic Wasp ◽

Specific Pattern ◽

Diploid Males ◽

Phenotypic Marker ◽

Group I ◽

Sex Locus

Abstract To test whether sex determination in the parasitic wasp Bracon sp. near hebetor (Hymenoptera: Braconidae) is based upon a single locus or multiple loci, a linkage map was constructed using random amplified polymorphic DNA (RAPD) markers. The map includes 71 RAPD markers and one phenotypic marker, blonde. Sex was scored in a manner consistent with segregation of a single “sex locus” under complementary sex determination (CSD), which is common in haplodiploid Hymenoptera. Under haplodiploidy, males arise from unfertilized haploid eggs and females develop from fertilized diploid eggs. With CSD, females are heterozygous at the sex locus; diploids that are homozygous at the sex locus become diploid males, which are usually inviable or sterile. Ten linkage groups were formed at a minimum LOD of 3.0, with one small linkage group that included the sex locus. To locate other putative quantitative trait loci (QTL) for sex determination, sex was also treated as a binary threshold character. Several QTL were found after conducting permutation tests on the data, including one on linkage group I that corresponds to the major sex locus. One other QTL of smaller effect had a segregation pattern opposite to that expected under CSD, while another putative QTL showed a female-specific pattern consistent with either a sex-differentiating gene or a sex-specific deleterious mutation. Comparisons are made between this study and the indepth studies on sex determination and sex differentiation in the closely related B. hebetor.

Download Full-text