Translocation of Y-linked genes to the dot chromosome in Drosophila pseudoobscura

Mol Biol Evol. 2010 Jul;27(7):1612-20. doi: 10.1093/molbev/msq045. Epub 2010 Feb 10.

Abstract

One of the most striking cases of sex chromosome reorganization in Drosophila occurred in the lineage ancestral to Drosophila pseudoobscura, where there was a translocation of Y-linked genes to an autosome. These genes went from being present only in males, never recombining, and having an effective population size of 0.5N to a state of autosomal linkage, where they are passed through both sexes, may recombine, and their effective population size has quadrupled. These genes appear to be functional, and they underwent a drastic reduction in intron size after the translocation. A Y-autosome translocation may pose problems in meiosis if the rDNA locus responsible for X-Y pairing had also moved to an autosome. In this study, we demonstrate that the Y-autosome translocation moved Y-linked genes onto the dot chromosome, a small, mainly heterochromatic autosome with some sex chromosome-like properties. The rDNA repeats occur exclusively on the X chromosome in D. pseudoobscura, but we found that the new Y chromosome of this species harbors four clusters bearing only the intergenic spacer region (IGS) of the rDNA repeats. This arrangement appears analogous to the situation in Drosophila simulans, where X-rDNA to Y-IGS pairing could be responsible for X-Y chromosome pairing. We postulate that the nascent D. pseudoobscura Y chromosome acquired and amplified copies of the IGS, suggesting a potential mechanism for X-Y pairing in D. pseudoobscura.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • DNA, Intergenic
  • DNA, Ribosomal / genetics*
  • Drosophila / classification
  • Drosophila / genetics*
  • Female
  • Genes, Insect / genetics*
  • Introns / genetics
  • Male
  • Repetitive Sequences, Nucleic Acid
  • Translocation, Genetic / genetics*
  • X Chromosome / genetics*
  • Y Chromosome / genetics*

Substances

  • DNA, Intergenic
  • DNA, Ribosomal