Dynamics Of Early Zygotic Dosage Compensation and a Characterization of Spiroplasmas Role in Drosophila Male-Killing

Abstract

Characterizing Early Zygotic Dosage Compensation in Drosophila melanogaster using RNA-Seq

Sexual reproduction in flies, mammals, and worms results in males and females receiving different numbers of X chromosomes. A chromosome wide regulatory process termed dosage compensation counteracts the differences in X-linked gene expression between sexes by balancing X-chromosome transcript levels. In Drosophila melanogaster, the Dosage Compensation Complex (DCC) forms in the presence of Msl-2 and activates a two-fold increase in gene expression. However multiple questions still remain regarding the function of the DCC as recent studies indicate the presence of an alternative dosage compensation mechanism. Sex lethal (Sxl), an RNA binding protein involved in sex determination is believed to play a role in this alternative model by regulating X-linked female transcripts. In this study we will examine the mechanism behind early zygotic dosage compensation using a novel high-throughput approach to sort male and female embryos during early embryogenesis. We use RNA-Seq to measure zygotic expression levels in male and female embryos. We then characterize Sxl and Msl-1 loss-of-function mutants to determine the mechanism behind early dosage compensation. Our study intends to further our understanding of sex specific transcription on a global scale during early Drosophila development.

Determining Spiroplasma MSRO’s role in Drosophila melanogaster male lethality

Spiroplasma MSRO are maternally transmitted bacteria that infect Drosophila melanogaster and induce apoptosis in male embryos during early embryogenesis. Previous reports have implicated the male dosage compensation complex (DCC) as a factor in male lethality as the loss of any DCC gene suppresses Spiroplasma induced apoptosis. In this study we characterize Spiroplasma’s impact on the male embryo’s molecular and morphogenetic development. We use RNA-Seq to measure transcript levels in infected male and female embryos during early embryogenesis. To determine if the loss of the dosage compensation system rescues transcript mis-regulation we quantify gene expression in homozygous Msl-1 embryos. We show that mis-regulation is sex specific and that Drosophila autosomal and X-linked genes are affected. We demonstrate that the loss of DCC functionality rescues transcript mis-regulation in infected male embryos. Our study intends to further our understanding of sex specific host-symbiont interactions.