Chromosome Studies on Eight Species of Sciara (Diptera) with Special Reference to Chromosome Changes of Evolutionary Significance. II (Continued)

McCarthy, Miles D.

doi:10.1086/281256

Cited by 8 publications

(3 citation statements)

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“…At least one other monogenic species, B. impatiens , is known to harbor an X-linked inversion polymorphism. Monogenic reproduction also occurs in many Bradysia species, including B. varians (10), B. spatitergum, B. molokaiensis (35) and B. paupera (107), as well as more distantly related Sciaridae including Scatopsciara nacta (38), Ctenosciara hawaiiensis, Lycoriella solispina (35), Corynoptera subtrivialis (10) and Rhyncosciara hollaenderi (44). In this respect, our finding that the B. coprophila X’ chromosome evolved <0.5 mya has intriguing consequences for understanding the evolution of this reproductive strategy.…”

Section: Discussionmentioning

confidence: 99%

“…Early cytological observations suggested that two monogenic species, B. coprophila and B. impatiens , possess single long inversions spanning most of the X chromosome (henceforth the inverted chromosome is denoted by X’), and that female-producing females are heterozygotes (14, 36). Polytene chromosome staining indicates that such inversions are absent in digenic species (37, 38) as well as in at least one species exhibiting mixed reproductive strategies (39). Through a series of cytogenetic studies, Crouse (15, 36, 40, 41) deduced the structures of the chromosomes in B. coprophila , including the approximate breakpoint locations of the X’ inversion.…”

Section: Introductionmentioning

confidence: 99%

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Recent evolution of a maternally-acting sex-determining supergene in a fly with single-sex broods

Baird

Urban

Mongue

et al. 2022

Preprint

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Sex determination is a key developmental process, yet it is remarkably variable across the tree of life. The dipteran family Sciaridae exhibits one of the most unusual sex determination systems in which mothers control offspring sex through selective elimination of paternal X chromosomes. Whereas in some members of the family females produce mixed-sex broods, others such as the dark-winged fungus gnat Bradysia coprophila are monogenic, with females producing single-sex broods. Female-producing females were previously found to be heterozygous for a large X-linked paracentric inversion (X'), which is maternally inherited and absent from male-producing females. Here we assembled and characterized the X' sequence. As close sequence homology between the X and X' made identification of the inversion challenging, we developed a k-mer-based approach to bin genomic reads before assembly. We confirmed that the inversion spans most of the X' chromosome (approximately 55Mb) and encodes around 3500 genes. Analysis of the divergence between the inversion and the homologous region of the X revealed that it originated very recently (<0.5 mya). Surprisingly, we found that the X' is more complex than previously thought and is likely to have undergone multiple rearrangements that have produced regions of varying ages, resembling a supergene composed of evolutionary strata. We found functional degradation of around 7.3% of genes within the region of recombination suppression, but no evidence of accumulation of repetitive elements. Our findings provide an indication that sex-linked inversions are driving turnover of the strange sex determination system in this family of flies.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Recent evolution of a maternally-acting sex-determining supergene in a fly with single-sex broods

Baird

Urban

Mongue

et al. 2022

Preprint

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show abstract

“…Early cytological observations suggested that two monogenic species, B. coprophila and Bradysia impatiens , possess single long inversions spanning most of the X chromosome (henceforth the inverted chromosome is denoted by X′), for which female-producing females are heterozygous ( Carson 1946 ; Crouse 1979 ). Polytene chromosome staining indicates that such inversions are absent in digenic species ( McCarthy 1945a , 1945b ) as well as in at least one species exhibiting mixed reproductive strategies ( Rocha and Perondini 2000 ). Through a series of cytogenetic studies, Crouse (1979) deduced the structures of the chromosomes in B. coprophila and demonstrated that the X′ inversion is paracentric and spans most of the length of the chromosome, leaving the two ends of the chromosome, which still synapse with the X, noninverted.…”

Section: Introductionmentioning

confidence: 99%

Recent Evolution of a Maternally Acting Sex-Determining Supergene in a Fly with Single-Sex Broods

Baird

Urban

Mongue

et al. 2023

Molecular Biology and Evolution

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Sex determination is a key developmental process, yet it is remarkably variable across the tree of life. The dipteran family Sciaridae exhibits one of the most unusual sex determination systems in which mothers control offspring sex through selective elimination of paternal X chromosomes. Whereas in some members of the family females produce mixed-sex broods, others such as the dark-winged fungus gnat Bradysia coprophila are monogenic, with females producing single-sex broods. Female-producing females were previously found to be heterozygous for a large X-linked paracentric inversion (X´), which is maternally inherited and absent from male-producing females. Here we assembled and characterized the X´ sequence. As close sequence homology between the X and X´ made identification of the inversion challenging, we developed a k-mer-based approach to bin genomic reads before assembly. We confirmed that the inversion spans most of the X´ chromosome (approximately 55Mb) and encodes around 3500 genes. Analysis of the divergence between the inversion and the homologous region of the X revealed that it originated very recently (<0.5 mya). Surprisingly, we found that the X´ is more complex than previously thought and is likely to have undergone multiple rearrangements that have produced regions of varying ages, resembling a supergene composed of evolutionary strata. We found functional degradation of around 7.3% of genes within the region of recombination suppression, but no evidence of accumulation of repetitive elements. Our findings provide an indication that sex-linked inversions are driving turnover of the strange sex determination system in this family of flies.

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Die cytologischen und genetischen Konsequenzen von Inversionen

Panitz¹

1960

Ergebnisse Der Biologie

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Chromosome Studies on Eight Species of Sciara (Diptera) with Special Reference to Chromosome Changes of Evolutionary Significance. II (Continued)

Cited by 8 publications

References 0 publications

Recent evolution of a maternally-acting sex-determining supergene in a fly with single-sex broods

Recent evolution of a maternally-acting sex-determining supergene in a fly with single-sex broods

Recent Evolution of a Maternally Acting Sex-Determining Supergene in a Fly with Single-Sex Broods

Die cytologischen und genetischen Konsequenzen von Inversionen

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