Background: Drosophila albomicans is a unique model organism for studying both sex chromosome and B chromosome evolution. A pair of its autosomes comprising roughly 40% of the whole genome has fused to the ancient X and Y chromosomes only about 0.12 million years ago, thereby creating the youngest and most gene-rich neo-sex system reported to date. This species also possesses recently derived B chromosomes that show non-Mendelian inheritance and significantly influence fertility.Methods: We sequenced male flies with B chromosomes at 124.5-fold genome coverage using next-generation sequencing. To characterize neo-Y specific changes and B chromosome sequences, we also sequenced inbred female flies derived from the same strain but without B's at 28.5-fold.Results: We assembled a female genome and placed 53% of the sequence and 85% of the annotated proteins into specific chromosomes, by comparison with the 12 Drosophila genomes. Despite its very recent origin, the non-recombining neo-Y chromosome shows various signs of degeneration, including a significant enrichment of non-functional genes compared to the neo-X, and an excess of tandem duplications relative to other chromosomes. We also characterized a B-chromosome linked scaffold that contains an actively transcribed unit and shows sequence similarity to the subcentromeric regions of both the ancient X and the neo-X chromosome.Conclusions: Our results provide novel insights into the very early stages of sex chromosome evolution and B chromosome origination, and suggest an unprecedented connection between the births of these two systems in D. albomicans.
Zhou Q, Zhu H, Huang Q, et al. Deciphering neo-sex and B chromosome evolution by the draft genome of Drosophila albomicans. BMC Genomics. 2012;13(1). doi:10.1186/1471-2164-13-109
Zhou, Q., Zhu, H., Huang, Q., Zhao, L., Zhang, G., Roy, S., … Bachtrog, D. (2012). Deciphering neo-sex and B chromosome evolution by the draft genome of Drosophila albomicans. BMC Genomics, 13(1). https://doi.org/10.1186/1471-2164-13-109
Zhou, Qi, Hongmei Zhu, Quanfei Huang, Li Zhao, Guo Zhang, Scott Roy, Beatriz Vicoso, et al. “Deciphering Neo-Sex and B Chromosome Evolution by the Draft Genome of Drosophila Albomicans.” BMC Genomics 13, no. 1 (2012). https://doi.org/10.1186/1471-2164-13-109.
Q. Zhou et al., “Deciphering neo-sex and B chromosome evolution by the draft genome of Drosophila albomicans,” BMC Genomics, vol. 13, no. 1, 2012.
Zhou Q, Zhu H, Huang Q, Zhao L, Zhang G, Roy S, Vicoso B, Xuan Z, Ruan J, Zhang Y, Zhao R, Ye C, Zhang X, Wang J, Wang W, Bachtrog D. 2012. Deciphering neo-sex and B chromosome evolution by the draft genome of Drosophila albomicans. BMC Genomics. 13(1).
Zhou, Qi, et al. “Deciphering Neo-Sex and B Chromosome Evolution by the Draft Genome of Drosophila Albomicans.” BMC Genomics, vol. 13, no. 1, BioMed Central, 2012, doi:10.1186/1471-2164-13-109.