scholarly journals Further characterization of the Odysseus locus of hybrid sterility in Drosophila: one gene is not enough.

Genetics ◽  
1995 ◽  
Vol 140 (1) ◽  
pp. 201-206 ◽  
Author(s):  
D E Perez ◽  
C I Wu
Keyword(s):  
Related Species ◽  
Genetic Background ◽  
Hybrid Sterility ◽  
Weak Effect ◽  
Hybrid Male ◽  
Hybrid Male Sterility ◽  
Closely Related Species ◽  
Drosophila Mauritiana ◽  
Average Gene

Abstract Previously we mapped by genetical and molecular means a gene that contributes to hybrid-male sterility between Drosophila mauritiana and D. simulans to the cytological interval of 16D. In this report, we refine the mapping of this gene, Odysseus (Ods) and show that it can be delineated to a region the size of an average gene. We further demonstrate that, while Ods appears to be a discrete element, it requires other nearby gene(s) to be cointrogressed to confer full hybrid sterility effect. This observation is in agreement with the view that reproductive isolation between closely related species of Drosophila is usually caused by several genes of weak effect from the same species that interact strongly among themselves as well as with the foreign genetic background.

scholarly journals The Broom of the Sorcerer's Apprentice: The Fine Structure of a Chromosomal Region Causing Reproductive Isolation Between Two Sibling Species of Drosophila

Genetics ◽  
1996 ◽  
Vol 143 (3) ◽  
pp. 1287-1298 ◽  
Author(s):  
Andrew W Davis ◽  
Chug-I Wu
Keyword(s):  
Reproductive Isolation ◽  
Sibling Species ◽  
Related Species ◽  
Hybrid Sterility ◽  
Drosophila Genome ◽  
Hybrid Male ◽  
Hybrid Male Sterility ◽  
Closely Related Species ◽  
Drosophila Mauritiana ◽  
Two Factors

Abstract How many genes contribute to reproductive isolation between closely related species? We determined the number of genes located in the 9D-12B region of the Drosophila mauritiana X chromosome that cause hybrid male sterility in a D. simulans background. Previous low resolution studies suggested that a single hybrid sterility factor was associated with this region. In this study, by taking advantage of a cluster of visible and DNA markers, we identified three D. mauritiana factors in this region and then subjected one of them to detailed analysis. This factor again turned out to be comprised of three factors; one of which, mapped to within 200 kb, may in fact be two factors. The title refers to this exercise of splitting sterile introgressions into ever smaller ones, each of which retains partial or full sterility effects. In a region representing a mere 3% of the Drosophila genome, no fewer than six loci of hybrid sterility were identified between two sibling species that have not shown clear divergence at the molecular level. These results suggest that levels of genetic divergence between closely related species may be quite high for functionally important traits even when the opposite is true for randomly chosen loci.

Genetic Complexity Underlying Hybrid Male Sterility in Drosophila

Genetics ◽  
2004 ◽  
Vol 166 (2) ◽  
pp. 789-796 ◽  
Author(s):  
Kyoichi Sawamura ◽  
John Roote ◽  
Chung-I Wu ◽  
Masa-Toshi Yamamoto
Keyword(s):  
Male Sterility ◽  
Related Species ◽  
Synergistic Effects ◽  
Female Sterility ◽  
Hybrid Male ◽  
Hybrid Female ◽  
Hybrid Male Sterility ◽  
Closely Related Species ◽  
Genetic Complexity ◽  
Recessive Genes

Abstract Recent genetic analyses of closely related species of Drosophila have indicated that hybrid male sterility is the consequence of highly complex synergistic effects among multiple genes, both conspecific and heterospecific. On the contrary, much evidence suggests the presence of major genes causing hybrid female sterility and inviability in the less-related species, D. melanogaster and D. simulans. Does this contrast reflect the genetic distance between species? Or, generally, is the genetic basis of hybrid male sterility more complex than that of hybrid female sterility and inviability? To clarify this point, the D. simulans introgression of the cytological region 34D-36A to the D. melanogaster genome, which causes recessive male sterility, was dissected by recombination, deficiency, and complementation mapping. The 450-kb region between two genes, Suppressor of Hairless and snail, exhibited a strong effect on the sterility. Males are (semi-)sterile if this region of the introgression is made homozygous or hemizygous. But no genes in the region singly cause the sterility; this region has at least two genes, which in combination result in male sterility. Further, the males are less fertile when heterozygous with a larger introgression, which suggests that dominant modifiers enhance the effects of recessive genes of male sterility. Such an epistatic view, even in the less-related species, suggests that the genetic complexity is special to hybrid male sterility.

scholarly journals Genetics of hybrid male sterility between drosophila sibling species: a complex web of epistasis is revealed in interspecific studies.

Genetics ◽  
1994 ◽  
Vol 138 (2) ◽  
pp. 329-341 ◽  
Author(s):  
M F Palopoli ◽  
C I Wu
Keyword(s):  
Male Sterility ◽  
X Chromosome ◽  
Functional Divergence ◽  
Hybrid Sterility ◽  
Sequence Divergence ◽  
Hybrid Male ◽  
Hybrid Male Sterility ◽  
Common Component ◽  
Drosophila Mauritiana ◽  
Linkage Relationships

Abstract To study the genetic differences responsible for the sterility of their male hybrids, we introgressed small segments of an X chromosome from Drosophila simulans into a pure Drosophila mauritiana genetic background, then assessed the fertility of males carrying heterospecific introgressions of varying size. Although this analysis examined less than 20% of the X chromosome (roughly 5% of the euchromatic portion of the D. simulans genome), and the segments were introgressed in only one direction, a minimum of four factors that contribute to hybrid male sterility were revealed. At least two of the factors exhibited strong epistasis: males carrying either factor alone were consistently fertile, whereas males carrying both factors together were always sterile. Distinct spermatogenic phenotypes were observed for sterile introgressions of different lengths, and it appeared that an interaction between introgressed segments also influenced the stage of spermatogenic defect. Males with one category of introgression often produced large quantities of motile sperm and were observed copulating, but never inseminated females. Evidently these two species have diverged at a large number of loci which have varied effects on hybrid male fertility. By extrapolation, we estimate that there are at least 40 such loci on the X chromosome alone. Because these species exhibit little DNA-sequence divergence at arbitrarily chosen loci, it seems unlikely that the extensive functional divergence observed could be due mainly to random genetic drift. Significant epistasis between conspecific genes appears to be a common component of hybrid sterility between recently diverged species of Drosophila. The linkage relationships of interacting factors could shed light on the role played by epistatic selection in the dynamics of the allele substitutions responsible for reproductive barriers between species.

Evidence for complex genic interactions between conspecific chromosomes underlying hybrid female sterility in the Drosophila simulans clade.

Genetics ◽  
1994 ◽  
Vol 137 (1) ◽  
pp. 191-199 ◽  
Author(s):  
A W Davis ◽  
E G Noonburg ◽  
C I Wu
Keyword(s):  
Hybrid Sterility ◽  
Drosophila Simulans ◽  
Female Sterility ◽  
Hybrid Male ◽  
Hybrid Female ◽  
Hybrid Male Sterility ◽  
Epistatic Interactions ◽  
X Chromosomes ◽  
F1 Hybrid ◽  
Drosophila Mauritiana

Abstract F1 hybrid females between the sibling species Drosophila simulans, Drosophila mauritiana and Drosophila sechellia are completely fertile. However, we have found that female sterility can be observed in F2 backcross females who are homozygous for D. simulans X chromosomes and homozygous for autosomal regions from either D. mauritiana or D. sechellia. Our results indicate that neither D. mauritiana autosome (2 or 3) can cause complete female sterility in a D. simulans background. The simultaneous presence of homozygous regions from both the second and third chromosomes of D. mauritiana, however, causes nearly complete female sterility which cannot be accounted for by their individual effects. The two autosomes of D. sechellia may show a similar pattern. From the same crosses, we also obtained evidence against a role for cytoplasmic or maternal effects in causing hybrid male sterility between these species. Taken with the results presented elsewhere, these observations suggest that epistatic interactions between conspecific genes in a hybrid background may be the prevalent mode of hybrid sterility between recently diverged species.

scholarly journals Mapping and characterization of a ‘speciation gene’ in Drosophila

1992 ◽  
Vol 59 (2) ◽  
pp. 73-80 ◽  
Author(s):  
H. Allen Orr
Keyword(s):  
Salivary Gland ◽  
Reproductive Isolation ◽  
Single Gene ◽  
Hybrid Sterility ◽  
Small Region ◽  
Male Sterile ◽  
Fourth Chromosome ◽  
Hybrid Male ◽  
Hybrid Male Sterility

SummaryAlmost nothing is known about the identity of the genes causing reproductive isolation between species. As a first step towards molecular isolation of a ‘speciation gene’, I mapped and partly characterized a gene causing hybrid male sterility in Drosophila. This analysis shows that sterility of D. melanogaster males who carry the ‘dot’ fourth chromosome from D. simulans is due entirely to a very small region of the D. simulans chromosome (including only about 5 salivary gland bands or approximately 250 kb of DNA). Thus the hybrid sterility effect of the D. simulans fourth chromosome is almost surely due to a single gene of very large effect (here named hms, hybrid male sterile). Hms is zygotically acting, and the D. simulans allele of hms is completely recessive. Furthermore, complementation tests suggest that hms is not an allele of any known locus in D. melanogaster.

scholarly journals Genetics of reproductive isolation in the Drosophila simulans clade: DNA marker-assisted mapping and characterization of a hybrid-male sterility gene, Odysseus (Ods).

Genetics ◽  
1993 ◽  
Vol 134 (1) ◽  
pp. 261-275 ◽  
Author(s):  
D E Perez ◽  
C I Wu ◽  
N A Johnson ◽  
M L Wu
Keyword(s):  
Male Sterility ◽  
Major Gene ◽  
Drosophila Simulans ◽  
Recombination Analysis ◽  
Hybrid Male ◽  
Hybrid Male Sterility ◽  
Complete Penetrance ◽  
Drosophila Mauritiana ◽  
Male Sterility Gene

Abstract In this study, we address the question of whether there exist major genes that cause complete male sterility in the interspecific hybrids of Drosophila and, if they do, how these genes may be characterized at the molecular level. Our approach is to introgress small segments of the X chromosome from Drosophila mauritiana (or Drosophila sechellia) into Drosophila simulans by repeated backcrosses for more than 20 generations. The introgressions are monitored by both visible mutations and a series of DNA markers. We compare the extent of introgressions that cause male sterility with those that do not. If a major sterility factor exists, there should be a sharp boundary between these two classes of introgressions and their breakpoints should demarcate such a gene. Furthermore, if male sterility is the only major fitness effect associated with the introgression, recombination analysis should yield a pattern predicted by the classical three-point cross. Both the genetic and molecular analyses suggest the presence of a major sterility factor from D. mauritiana, which we named Odysseus (Ods), in the cytological interval of 16D. We thus formalize three criteria for inferring the existence of a major gene within an introgression: (1) complete penetrance of sterility, (2) complementarity in recombination analysis, and (3) physical demarcation. Introgressions of Ods from D. sechellia do not cause sterility. Twenty-two introgressions in our collection have breakpoints in this interval of about 500 kb, making it possible to delineate Ods more precisely for molecular identification. The recombination analysis also reveals the complexity of the introgressed segments--even relatively short ones may contain a second male sterility factor and partial viability genes and may also interfere with crossovers. The spermatogenic defects associated with Ods and/or a second factor were characterized by phase-contrast microscopy.

scholarly journals Hidden Effects of X Chromosome Introgressions on Spermatogenesis in Drosophila simulans × D. mauritiana Hybrids Unveiled by Interactions Among Minor Genetic Factors

Genetics ◽  
1998 ◽  
Vol 150 (2) ◽  
pp. 745-754 ◽  
Author(s):  
Xulio R Maside ◽  
José P Barral ◽  
Horacio F Naveira
Keyword(s):  
Male Sterility ◽  
X Chromosome ◽  
Seminal Vesicles ◽  
Genetic Dissection ◽  
Research Strategies ◽  
Hybrid Male ◽  
Hybrid Male Sterility ◽  
Epistatic Interactions ◽  
Drosophila Mauritiana ◽  
Chromosome Segments

Abstract One of the most frequent outcomes of interspecific hybridizations in Drosophila is hybrid male sterility. Genetic dissection of this reproductive barrier has revealed that the number of responsible factors is very high and that these factors are frequently engaged in complex epistatic interactions. Traditionally, research strategies have been based on contrasting introgressions of chromosome segments that produce male sterility with those that allow fertility. Few studies have investigated the phenotypes associated with the boundary between fertility and sterility. In this study, we cointrogressed three different X chromosome segments from Drosophila mauritiana into D. simulans. Hybrid males with these three segments are usually fertile, by conventional fertility assays. However, their spermatogenesis shows a significant slowdown, most manifest at lower temperatures. Each of the three introgressed segments retards the arrival of sperm to the seminal vesicles. Other small disturbances in spermatogenesis are evident, which altogether lead to an overall reduction in the amount of motile sperm in their seminal vesicles. These results suggest that a delay in the timing of spermatogenesis, which might be brought about by the cumulative action of many different factors of minor segment, may be the primary cause of hybrid male sterility.

scholarly journals Age and genetic background modify hybrid male sterility in house mice

2020 ◽  
Author(s):  
Samuel J. Widmayer ◽  
Mary Ann Handel ◽  
David L. Aylor
Keyword(s):  
Male Sterility ◽  
House Mouse ◽  
Genetic Background ◽  
Genetic Architecture ◽  
Hybrid Male ◽  
Hybrid Male Sterility ◽  
X Chromosomes ◽  
Age Related ◽  
Age Dependent ◽  
In The Wild

AbstractHybrid male sterility (HMS) contributes to reproductive isolation commonly observed among house mouse (Mus musculus) subspecies, both in the wild and in laboratory crosses. Incompatibilities involving specific Prdm9 alleles and certain Chromosome (Chr) X genotypes are known determinants of fertility and HMS, and previous work in the field has demonstrated that genetic background modifies these two major loci. We constructed hybrids that have identical genotypes at Prdm9 and identical X chromosomes, but differ widely across the rest of the genome. In each case, we crossed female PWK/PhJ mice representative of the M. m. musculus subspecies to males from a classical inbred strain representative of M. m. domesticus: 129S1/SvImJ, A/J, C57BL/6J, or DBA/2J. We detected three distinct trajectories of fertility among the hybrids using breeding experiments. The PWK129S1 males were always infertile. PWKDBA2 males were fertile, despite their genotypes at the major HMS loci. We also observed age-dependent changes in fertility parameters across multiple genetic backgrounds. The PWKB6 and PWKAJ males were always infertile before 15 weeks and after 35 weeks, yet some PWKB6 and PWKAJ males were fertile between fifteen and 35 weeks. This observation could resolve previous contradictory reports about the fertility of PWKB6. Taken together, these results point to multiple segregating HMS modifier alleles, some of which have age-related modes of action. The ultimate identification of these alleles and their age-related mechanisms will advance understanding both of the genetic architecture of HMS and of how reproductive barriers are maintained between house mouse subspecies.

The Ornithodoros capensis group (Acari: Argasidae): a morphological diagnosis and molecular characterization of O. capensis sensu stricto from Queimada Grande Island, Brazil 

2017 ◽  
Vol 22 (1) ◽  
pp. 28 ◽  
Author(s):  
Sebastián Muñoz-Leal ◽  
Ricardo A. Dias ◽  
Carlos R. Abrahão ◽  
Marcelo B. Labruna
Keyword(s):  
Molecular Characterization ◽  
Related Species ◽  
Morphological Analysis ◽  
Bacterial Pathogens ◽  
Sensu Stricto ◽  
Closely Related Species ◽  
Paulo State ◽  
Morphological Diagnosis ◽  
First Time

Ornithodoros capensis sensu lato (s. l.) is a worldwide-distributed group of soft ticks that parasitize birds in insular and continental lands. It is currently composed of 11 morphologically closely related species. Several viral and bacterial pathogens, and particularly Coxiella-like endosymbiont organisms have been described coexisting with ticks of this group. Since it last report in 1983, the presence of O. capensis s. l. in Brazil has remained undocumented. By a morphological analysis of larvae and a molecular characterization of ticks and Coxiella genes we describe for the first time O. capensis sensu stricto in Brazil from specimens collected on Queimada Grande Island, in São Paulo state.

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