Limits...
Numerous transitions of sex chromosomes in Diptera.

Vicoso B, Bachtrog D - PLoS Biol. (2015)

Bottom Line: Transcriptome analysis shows that dosage compensation has evolved multiple times in flies, consistently through up-regulation of the single X in males.However, X chromosomes generally show a deficiency of genes with male-biased expression, possibly reflecting sex-specific selective pressures.These species thus provide a rich resource to study sex chromosome biology in a comparative manner and show that similar selective forces have shaped the unique evolution of sex chromosomes in diverse fly taxa.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative Biology, University of California Berkeley, Berkeley, California, United States of America.

ABSTRACT
Many species groups, including mammals and many insects, determine sex using heteromorphic sex chromosomes. Diptera flies, which include the model Drosophila melanogaster, generally have XY sex chromosomes and a conserved karyotype consisting of six chromosomal arms (five large rods and a small dot), but superficially similar karyotypes may conceal the true extent of sex chromosome variation. Here, we use whole-genome analysis in 37 fly species belonging to 22 different families of Diptera and uncover tremendous hidden diversity in sex chromosome karyotypes among flies. We identify over a dozen different sex chromosome configurations, and the small dot chromosome is repeatedly used as the sex chromosome, which presumably reflects the ancestral karyotype of higher Diptera. However, we identify species with undifferentiated sex chromosomes, others in which a different chromosome replaced the dot as a sex chromosome or in which up to three chromosomal elements became incorporated into the sex chromosomes, and others yet with female heterogamety (ZW sex chromosomes). Transcriptome analysis shows that dosage compensation has evolved multiple times in flies, consistently through up-regulation of the single X in males. However, X chromosomes generally show a deficiency of genes with male-biased expression, possibly reflecting sex-specific selective pressures. These species thus provide a rich resource to study sex chromosome biology in a comparative manner and show that similar selective forces have shaped the unique evolution of sex chromosomes in diverse fly taxa.

No MeSH data available.


Related in: MedlinePlus

Detecting neo-sex chromosomes.A,B,C: Male/female coverage versus percentage of SNPs found in males (SNPs in the male sample/total number of SNPs) for scaffolds from the autosomes (black), fully differentiated (red), and newly evolved (blue) X chromosomes of Drosophila miranda (A), Drosophila albomicans (B), and Drosophila busckii (C). D: The neo-X (in blue) of Scaptodrosophila lebanonensis (D) is fully degenerated; it shows a 2-fold reduction in male versus female expression but no excess of male SNPs, similar to the ancestral X. E,F: The Muller elements of Holcocephala fusca (E) and Mayetiola destructor (F) that have intermediate levels of male to female coverage, in blue, have SNP patterns that are inconsistent with newly derived sex-chromosomes (no excess of male SNPs). G,H: No evidence of differentiated sex chromosomes using coverage or SNPs in Calliphora erythrocephala (G) and Megaselia abdita (H). The lines intersect at the median, and extend to the 10% and 90% percentiles. Data to generate this graph are to be found in file “S1 Data” and “S2 Data.”
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4400102&req=5

pbio.1002078.g002: Detecting neo-sex chromosomes.A,B,C: Male/female coverage versus percentage of SNPs found in males (SNPs in the male sample/total number of SNPs) for scaffolds from the autosomes (black), fully differentiated (red), and newly evolved (blue) X chromosomes of Drosophila miranda (A), Drosophila albomicans (B), and Drosophila busckii (C). D: The neo-X (in blue) of Scaptodrosophila lebanonensis (D) is fully degenerated; it shows a 2-fold reduction in male versus female expression but no excess of male SNPs, similar to the ancestral X. E,F: The Muller elements of Holcocephala fusca (E) and Mayetiola destructor (F) that have intermediate levels of male to female coverage, in blue, have SNP patterns that are inconsistent with newly derived sex-chromosomes (no excess of male SNPs). G,H: No evidence of differentiated sex chromosomes using coverage or SNPs in Calliphora erythrocephala (G) and Megaselia abdita (H). The lines intersect at the median, and extend to the 10% and 90% percentiles. Data to generate this graph are to be found in file “S1 Data” and “S2 Data.”

Mentions: Different chromosomal elements (designated elements A–F) have become sex-linked in different families of Diptera (indicated by different colors along the phylogeny). Elements were classified as X-linked when they were over-represented among our candidate X scaffolds, based on their male/female coverage (see Materials and Methods and S1–S3 Figs.) or if they showed an excess of SNPs in the heterogametic sex (Figs. 2 and S5). Bold lines indicate a transition of a sex chromosome at a particular branch of the tree and was inferred using parsimony. Dashed lines indicate instances where partial Muller elements segregate as a sex chromosome (see Figs. 2 and S5, S6 and S1 Table for more details). Data to generate the phylogeny are to be found in file “S2 Text” and “S3 Text.” Images drawn by Doris Bachtrog.


Numerous transitions of sex chromosomes in Diptera.

Vicoso B, Bachtrog D - PLoS Biol. (2015)

Detecting neo-sex chromosomes.A,B,C: Male/female coverage versus percentage of SNPs found in males (SNPs in the male sample/total number of SNPs) for scaffolds from the autosomes (black), fully differentiated (red), and newly evolved (blue) X chromosomes of Drosophila miranda (A), Drosophila albomicans (B), and Drosophila busckii (C). D: The neo-X (in blue) of Scaptodrosophila lebanonensis (D) is fully degenerated; it shows a 2-fold reduction in male versus female expression but no excess of male SNPs, similar to the ancestral X. E,F: The Muller elements of Holcocephala fusca (E) and Mayetiola destructor (F) that have intermediate levels of male to female coverage, in blue, have SNP patterns that are inconsistent with newly derived sex-chromosomes (no excess of male SNPs). G,H: No evidence of differentiated sex chromosomes using coverage or SNPs in Calliphora erythrocephala (G) and Megaselia abdita (H). The lines intersect at the median, and extend to the 10% and 90% percentiles. Data to generate this graph are to be found in file “S1 Data” and “S2 Data.”
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4400102&req=5

pbio.1002078.g002: Detecting neo-sex chromosomes.A,B,C: Male/female coverage versus percentage of SNPs found in males (SNPs in the male sample/total number of SNPs) for scaffolds from the autosomes (black), fully differentiated (red), and newly evolved (blue) X chromosomes of Drosophila miranda (A), Drosophila albomicans (B), and Drosophila busckii (C). D: The neo-X (in blue) of Scaptodrosophila lebanonensis (D) is fully degenerated; it shows a 2-fold reduction in male versus female expression but no excess of male SNPs, similar to the ancestral X. E,F: The Muller elements of Holcocephala fusca (E) and Mayetiola destructor (F) that have intermediate levels of male to female coverage, in blue, have SNP patterns that are inconsistent with newly derived sex-chromosomes (no excess of male SNPs). G,H: No evidence of differentiated sex chromosomes using coverage or SNPs in Calliphora erythrocephala (G) and Megaselia abdita (H). The lines intersect at the median, and extend to the 10% and 90% percentiles. Data to generate this graph are to be found in file “S1 Data” and “S2 Data.”
Mentions: Different chromosomal elements (designated elements A–F) have become sex-linked in different families of Diptera (indicated by different colors along the phylogeny). Elements were classified as X-linked when they were over-represented among our candidate X scaffolds, based on their male/female coverage (see Materials and Methods and S1–S3 Figs.) or if they showed an excess of SNPs in the heterogametic sex (Figs. 2 and S5). Bold lines indicate a transition of a sex chromosome at a particular branch of the tree and was inferred using parsimony. Dashed lines indicate instances where partial Muller elements segregate as a sex chromosome (see Figs. 2 and S5, S6 and S1 Table for more details). Data to generate the phylogeny are to be found in file “S2 Text” and “S3 Text.” Images drawn by Doris Bachtrog.

Bottom Line: Transcriptome analysis shows that dosage compensation has evolved multiple times in flies, consistently through up-regulation of the single X in males.However, X chromosomes generally show a deficiency of genes with male-biased expression, possibly reflecting sex-specific selective pressures.These species thus provide a rich resource to study sex chromosome biology in a comparative manner and show that similar selective forces have shaped the unique evolution of sex chromosomes in diverse fly taxa.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative Biology, University of California Berkeley, Berkeley, California, United States of America.

ABSTRACT
Many species groups, including mammals and many insects, determine sex using heteromorphic sex chromosomes. Diptera flies, which include the model Drosophila melanogaster, generally have XY sex chromosomes and a conserved karyotype consisting of six chromosomal arms (five large rods and a small dot), but superficially similar karyotypes may conceal the true extent of sex chromosome variation. Here, we use whole-genome analysis in 37 fly species belonging to 22 different families of Diptera and uncover tremendous hidden diversity in sex chromosome karyotypes among flies. We identify over a dozen different sex chromosome configurations, and the small dot chromosome is repeatedly used as the sex chromosome, which presumably reflects the ancestral karyotype of higher Diptera. However, we identify species with undifferentiated sex chromosomes, others in which a different chromosome replaced the dot as a sex chromosome or in which up to three chromosomal elements became incorporated into the sex chromosomes, and others yet with female heterogamety (ZW sex chromosomes). Transcriptome analysis shows that dosage compensation has evolved multiple times in flies, consistently through up-regulation of the single X in males. However, X chromosomes generally show a deficiency of genes with male-biased expression, possibly reflecting sex-specific selective pressures. These species thus provide a rich resource to study sex chromosome biology in a comparative manner and show that similar selective forces have shaped the unique evolution of sex chromosomes in diverse fly taxa.

No MeSH data available.


Related in: MedlinePlus