title: Natural variation of the Y chromosome suppresses sex ratio distortion and modulates testis-specific gene expression in Drosophila simulans.
abstract: X-linked sex-ratio distorters that disrupt spermatogenesis can cause a deficiency in functional Y-bearing sperm and a female-biased sex ratio. Y-linked modifiers that restore a normal sex ratio might be abundant and favored when a X-linked distorter is present. Here we investigated natural variation of Y-linked suppressors of sex-ratio in the Winters systems and the ability of these chromosomes to modulate gene expression in Drosophila simulans. Seventy-eight Y chromosomes of worldwide origin were assayed for their resistance to the X-linked sex-ratio distorter gene Dox. Y chromosome diversity caused males to sire ∼63% to ∼98% female progeny. Genome-wide gene expression analysis revealed hundreds of genes differentially expressed between isogenic males with sensitive (high sex ratio) and resistant (low sex ratio) Y chromosomes from the same population. Although the expression of about 75% of all testis-specific genes remained unchanged across Y chromosomes, a subset of post-meiotic genes was upregulated by resistant Y chromosomes. Conversely, a set of accessory gland-specific genes and mitochondrial genes were downregulated in males with resistant Y chromosomes. The D. simulans Y chromosome also modulated gene expression in XXY females in which the Y-linked protein-coding genes are not transcribed. The data suggest that the Y chromosome might exert its regulatory functions through epigenetic mechanisms that do not require the expression of protein-coding genes. The gene network that modulates sex ratio distortion by the Y chromosome is poorly understood, other than that it might include interactions with mitochondria and enriched for genes expressed in post-meiotic stages of spermatogenesis.
authors.affiliation: Molecular and Integrative Physiological Sciences, Environmental Health, Harvard School of Public Health, Boston, MA, USA.
authors.forename: A T
authors.initials: AT
authors.lastname: Branco
authors.forename: Y
authors.initials: Y
authors.lastname: Tao
authors.forename: D L
authors.initials: DL
authors.lastname: Hartl
authors.forename: B
authors.initials: B
authors.lastname: Lemos
mesh_terms: D000818:Animals; D059006:Chromosomes, Insect / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation; D004330:Drosophila / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D008297:Male; D009928:Organ Specificity; D012744:Sex Ratio; D013737:Testis / Q000378:metabolism; D014998:Y Chromosome / Q000235:genetics* / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins