Chromosome Painting Does Not Support a Sex Chromosome Turnover in Lacerta agilis Linnaeus, 1758

Abstract

Reptiles show a remarkable diversity of sex determination mechanisms and sex chromosome systems, derived from different autosomal pairs. The origin of the ZW sex chromosomes of Lacerta agilis, a widespread Eurasian lizard species, is a matter of discussion: is it a small macrochromosome from the 11-18 group common to all lacertids, or does this species have a unique ZW pair derived from the large chromosome 5? Using independent molecular cytogenetic methods, we investigated the karyotype of L. agilis exigua from Siberia, Russia, to identify the sex chromosomes. FISH with a flow-sorted chromosome painting probe derived from L. strigata and specific to chromosomes 13, 14, and Z confirmed that the Z chromosome of L. agilis is a small macrochromosome, the same as in L. strigata. FISH with the telomeric probe showed an extensive accumulation of the telomere-like repeat in the W chromosome in agreement with previous studies, excluding the possibility that the lineages of L. agilis studied in different works could have different sex chromosome systems due to a putative intra-species polymorphism. Our results reinforce the idea of the stability of the sex chromosomes and lack of evidence for sex-chromosome turnovers in known species of Lacertidae.

Evolutionary Variability of W-Linked Repetitive Content in Lacertid Lizards

“…prasina and Ta. dorsalis to this long list covering over 20% of currently recognized lacertid lizards [44]. Nevertheless, the data on the sequence content of the W chromosome and the cytogenetic identification of the Z chromosomes in lacertid karyotypes are scarce.…”

“…In this context, we selected the lizards of the family Lacertidae to explore the variability of the repetitive content of sex chromosomes between species across a wide phylogenetic scale in another model system. Previous cytogenetic studies demonstrated that all studied lacertids have highly differentiated ZZ/ZW sex chromosomes [34][35][36][37][38][39][40][41][42][43][44]. The majority of chromosomes in lacertids are acrocentric gradually decreasing in size.…”

“…The size of the W chromosome varies among lacertid species from small to medium [34,36,45]. In addition, the W chromosome seems to be enriched in satellite motifs in Acanthodactylus lineomaculatus, Eremias velox, and several species from the genera Lacerta and Timon [38,[40][41][42][43][44]. The Z chromosome is also acrocentric, small to medium in size in E. velox [46], and with more than 800 protein-coding genes in Lacerta agilis and Podarcis muralis [47,48].…”

Genome Complexity Reduction High-Throughput Genome Sequencing of Green Iguana (Iguana iguana) Reveal a Paradigm Shift in Understanding Sex-Chromosomal Linkages on Homomorphic X and Y Sex Chromosomes

“…This finding leads to the prediction that the green iguana in the two studies showed different linkages of sex-chromosome systems based on turnover from another autosomal pair. However, this scenario is difficult to envisage because the results of chromosome painting do not support sex-chromosome turnover in lizards of Iguanoidea (Lisachov et al, 2020). An additional possibility might be an intraspecific polymorphism in sex-determination systems, as in the case of the Japanese wrinkled frog Glandirana rugosa (Ogata et al, 2018).…”

Revisiting the Karyotype Evolution of Neotropical Boid Snakes: A Puzzle Mediated by Chromosomal Fissions

“…Given both scenarios of karyotype evolution proposed for neotropical boids, we carried out a cross-species chromosomal investigation performing chromosomal paintings in karyotypes of different Boidae species to decipher events of chromosome rearrangements associated with the evolutionary processes and diversification of this group. Cross-species chromosomal painting is a valuable comparative genomic tool in accessing and deciphering the dynamics of karyotype and genome evolution [ 31 , 32 , 33 ]. In this way, we used representative species of the genera Boa , Corallus , Eunectes , and Epicrates , covering all diploid numbers (2n = 36, 40 and 44) known for the family.…”