RT Journal Article
SR Electronic
T1 Extreme heterogeneity in sex chromosome differentiation and dosage compensation in livebearers
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 589788
DO 10.1101/589788
A1 Iulia Darolti
A1 Alison E. Wright
A1 Benjamin A. Sandkam
A1 Jake Morris
A1 Natasha I. Bloch
A1 Marta Farré
A1 Rebecca C. Fuller
A1 Godfrey R. Bourne
A1 Denis M. Larkin
A1 Felix Breden
A1 Judith E. Mank
YR 2019
UL http://biorxiv.org/content/early/2019/03/28/589788.abstract
AB Once recombination is halted between the X and Y chromosome, sex chromosomes begin to differentiate and transition to heteromorphism. While there is a remarkable variation across clades in the degree of sex chromosome divergence, far less is known about variation in sex chromosome differentiation within clades. Here, we combined whole genome and transcriptome sequencing data to characterise the structure and conservation of sex chromosome systems across Poeciliidae, the livebearing clade that includes guppies. We found that the Poecilia reticulata XY system is much older than previously thought, being shared not only with its sister species, Poecilia wingei, but also with Poecilia picta, which diverged 30 mya. Despite the shared ancestry, we uncovered an extreme heterogeneity across these species in the proportion of the sex chromosome with suppressed recombination, and the degree of Y chromosome decay. The sex chromosomes in P. reticulata are largely homomorphic, with recombination persisting over a substantial fraction. However, the sex chromosomes in P. picta are completely non-recombining and strikingly heteromorphic. ln addition to being highly divergent, the sex chromosome system in P. picta includes a neo-sex chromosome, the result of a fusion between the ancestral sex chromosome and part of chromosome 7. Remarkably, the profound degradation of the ancestral Y chromosome in P. picta is counterbalanced by the evolution of complete dosage compensation in this species, the first such documented case in teleost fish. Our results offer important insight into the initial stages of sex chromosome evolution and dosage compensation.