Assembly of polymorphic Y chromosomes reveals molecular basis of variation in male body size

• The Y chromosome of males is theorized to facilitate the evolution of sexual dimorphism by accumulating sexually antagonistic loci, but empirical support is limited. In the seed beetle Callosobruchus maculatus, variation in sexually antagonistic body size is linked to at least two segregating Y haplotypes in males that facilitated rapid laboratory evolution of sexual size dimorphism. Here we assemble previously uncharacterized C. maculatus sex chromosome sequences and identify molecular differences between the two predicted Y haplotypes. The Y chromosome of C. maculatus shows typical hallmarks of degeneration: it is ampliconic and approximately 80% smaller than the X. Nevertheless, the Y harbors over 400 genes with a mixed autosomal and X chromosome ancestry that are enriched with metabolic, developmental and gene regulatory functions. Crucially, we find that besides an autosomal copy of the gene target of rapamycin (TOR), males carry an additional TOR copy on the Y chromosome. TOR is a conserved regulator of growth across taxa, and a Y-linked copy of TOR thus provides a male specific opportunity to alter body size. The two identified Y haplotypes show fixed single nucleotide differences in or in close proximity to over 100 genes, but also copy number variation for TOR, where the more frequent (~95%) Y haplotype that causes increased sexual size dimorphism has two additional TOR copies. These results suggest that part of the sexual conflict over body size has been mitigated by autosome to Y translocation of TOR followed by gene duplications that further increased sexual dimorphism.

Ämnesord

NATURVETENSKAP  -- Biologi -- Evolutionsbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Evolutionary Biology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Genetik (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Genetics (hsv//eng)

Nyckelord

Y chromosome

Y polymorphism

sex chromosome

sexual dimorphism

Callosobruchus maculatus

sexual conflict

Biology with specialization in Evolutionary Genetics

Biologi med inriktning mot evolutionär genetik

Publikations- och innehållstyp

vet (ämneskategori)

ovr (ämneskategori)