Evolutionary dynamics of Anolis sex chromosomes revealed by sequencing of flow sorting-derived microchromosome-specific DNA

Abstract

Squamate reptiles show a striking diversity in modes of sex determination, including both genetic (XY or ZW) and temperature-dependent sex determination systems. The genomes of only a handful of species have been sequenced, analyzed and assembled including the genome of Anolis carolinensis. Despite a high genome coverage, only macrochromosomes of A. carolinensis were assembled whereas the content of most microchromosomes remained unclear. Most of the Anolis species have homomorphic XY sex chromosome system. However, some species have large heteromorphic XY chromosomes (e.g., A. sagrei) and even multiple sex chromosomes systems (e.g. A. pogus), that were shown to be derived from fusions of the ancestral XY with microautosomes. We applied next generation sequencing of flow sorting-derived chromosome-specific DNA pools to characterize the content and composition of microchromosomes in A. carolinensis and A. sagrei. Comparative analysis of sequenced chromosome-specific DNA pools revealed that the A. sagrei XY sex chromosomes contain regions homologous to several microautosomes of A. carolinensis. We suggest that the sex chromosomes of A. sagrei are derived by fusions of the ancestral sex chromosome with three microautosomes and subsequent loss of some genetic content on the Y chromosome.

Isolating Chromosomes of the Komodo Dragon: New Tools for Comparative Mapping and Sequence Assembly

“…However, a combination of NGS and flow sorting was used successfully for chromosomal genomics studies in wheat and barley [e.g., Šimková et al, 2008;Mayer et al, 2011;Hernandez et al, 2012;Martis et al, 2012;Cápal et al, 2015;Sánchez-Martín et al, 2016] and a few mammalian species, including the Tasmanian devil [Murchison et al, 2012], Chinese hamster [Brinkrolf et al, 2013], gorilla [Tomaszkiewicz et al, 2016], cervids , and mouse [Sudbery et al, 2009]. In reptiles, shotgun sequencing of isolated chromosomes was performed only recently by Kichigin et al [2016] to determine the sequence of A. sagrei and A. carolinensis microchromosomes and extend the work done on macrochromosomes by Alföldi et al [2011]. However, a comprehensive high-resolution chromosomal map built using an NGS/flow sorting approach has yet to be developed for nonavian reptiles.…”

Heteromorphism of “Homomorphic” Sex Chromosomes in Two Anole Species (Squamata, Dactyloidae) Revealed by Synaptonemal Complex Analysis

“…Some anole lineages (e.g., Norops , Ctenonotus ) have undergone a series of chromosome fusions and fissions (2n = 28-30, 2n = 40), which have led to the appearance of new macrochromosomes [Castiglia et al, 2013]. These species possess derived sex chromosomes which are composed of the ancestral anole XY chromosomes and autosomes translocated to them Kichigin et al, 2016]. It is unknown whether the newly translocated regions are already involved in the differentiation between the X and Y chromosomes.…”

Insights into Emydid Turtle Cytogenetics: The European Pond Turtle as a Model Species

“…Comparative genomic hybridization (CGH) was used to test for a cryptic GSD system. These data allow a better understanding of karyotype evolution in Emydidae and will aid future genome sequencing and anchoring efforts [e.g., Alföldi et al, 2011;Badenhorst et al, 2015;Damas et al, 2016;Kichigin et al, 2016;Rando et al, 2018].…”