scholarly journals Differences in Homomorphic Sex Chromosomes Are Associated with Population Divergence in Sex Determination in Carinascincus ocellatus (Scincidae: Lygosominae)

Cells ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 291
Author(s):  
Peta Hill ◽  
Foyez Shams ◽  
Christopher P. Burridge ◽  
Erik Wapstra ◽  
Tariq Ezaz
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Population Divergence ◽  
Sex Chromosome Evolution ◽  
Evolutionary Transitions ◽  
Evolutionary Origins ◽  
Probe Set

Sex determination directs development as male or female in sexually reproducing organisms. Evolutionary transitions in sex determination have occurred frequently, suggesting simple mechanisms behind the transitions, yet their detail remains elusive. Here we explore the links between mechanisms of transitions in sex determination and sex chromosome evolution at both recent and deeper temporal scales (<1 Myr; ~79 Myr). We studied a rare example of a species with intraspecific variation in sex determination, Carinascincus ocellatus, and a relative, Liopholis whitii, using c-banding and mapping of repeat motifs and a custom Y chromosome probe set to identify the sex chromosomes. We identified both unique and conserved regions of the Y chromosome among C. ocellatus populations differing in sex determination. There was no evidence for homology of sex chromosomes between C. ocellatus and L. whitii, suggesting independent evolutionary origins. We discuss sex chromosome homology between members of the subfamily Lygosominae and propose links between sex chromosome evolution, sex determination transitions, and karyotype evolution.

scholarly journals Identifying sex-linked markers in Litoria aurea: a novel approach to understanding sex chromosome evolution in an amphibian

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Jarrod Sopniewski ◽  
Foyez Shams ◽  
Benjamin C. Scheele ◽  
Ben J. Kefford ◽  
Tariq Ezaz
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Pseudoautosomal Region ◽  
Nucleotide Polymorphisms ◽  
Sex Chromosome Evolution ◽  
Litoria Aurea ◽  
Novel Approach

Abstract Few taxa exhibit the variability of sex-determining modes as amphibians. However, due to the presence of homomorphic sex chromosomes in many species, this phenomenon has been difficult to study. The Australian frog, Litoria aurea, has been relatively well studied over the past 20 years due to widespread declines largely attributable to chytrid fungus. However, it has been subject to few molecular studies and its mode of sex determination remained unknown. We applied DArTseq™ to develop sex-linked single nucleotide polymorphisms (SNPs) and restriction fragment presence/absence (PA) markers in 44 phenotypically sexed L. aurea individuals from the Molonglo River in NSW, Australia. We conclusively identified a male heterogametic (XX-XY) sex determination mode in this species, identifying 11 perfectly sex-linked SNP and six strongly sex-linked PA markers. We identified a further 47 moderately sex-linked SNP loci, likely serving as evidence indicative of XY recombination. Furthermore, within these 47 loci, a group of nine males were found to have a feminised Y chromosome that significantly differed to all other males. We postulate ancestral sex-reversal as a means for the evolution of this now pseudoautosomal region on the Y chromosome. Our findings present new evidence for the ‘fountain of youth’ hypothesis for the retention of homomorphic sex chromosomes in amphibians and describe a novel approach for the study of sex chromosome evolution in amphibia.

scholarly journals Sex chromosome evolution: historical insights and future perspectives

2017 ◽  
Vol 284 (1854) ◽  
pp. 20162806 ◽  
Author(s):  
Jessica K. Abbott ◽  
Anna K. Nordén ◽  
Bengt Hansson
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Empirical Studies ◽  
Analytical Models ◽  
Specific Gene ◽  
Sex Chromosome Evolution ◽  
Current Thinking

Many separate-sexed organisms have sex chromosomes controlling sex determination. Sex chromosomes often have reduced recombination, specialized (frequently sex-specific) gene content, dosage compensation and heteromorphic size. Research on sex determination and sex chromosome evolution has increased over the past decade and is today a very active field. However, some areas within the field have not received as much attention as others. We therefore believe that a historic overview of key findings and empirical discoveries will put current thinking into context and help us better understand where to go next. Here, we present a timeline of important conceptual and analytical models, as well as empirical studies that have advanced the field and changed our understanding of the evolution of sex chromosomes. Finally, we highlight gaps in our knowledge so far and propose some specific areas within the field that we recommend a greater focus on in the future, including the role of ecology in sex chromosome evolution and new multilocus models of sex chromosome divergence.

scholarly journals Early sex-chromosome evolution in the diploid dioecious plant Mercurialis annua

2017 ◽  
Author(s):  
Paris Veltsos ◽  
Kate E. Ridout ◽  
Melissa A. Toups ◽  
Santiago C. González-Martínez ◽  
Aline Muyle ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Gene Loss ◽  
Sex Chromosome ◽  
Sequence Divergence ◽  
Sex Chromosome Evolution ◽  
Dioecious Plant ◽  
Suppressed Recombination ◽  
Mercurialis Annua

AbstractSuppressed recombination around a sex-determining locus allows divergence between homologous sex chromosomes and the functionality of their genes. Here, we reveal patterns of the earliest stages of sex-chromosome evolution in the diploid dioecious herb Mercurialis annua on the basis of cytological analysis, de novo genome assembly and annotation, genetic mapping, exome resequencing of natural populations, and transcriptome analysis. Both genetic mapping and exome resequencing of individuals across the species range independently identified the largest linkage group, LG1, as the sex chromosome. Although the sex chromosomes of M. annua are karyotypically homomorphic, we estimate that about a third of the Y chromosome has ceased recombining, a region containing 568 transcripts and spanning 22.3 cM in the corresponding female map. Patterns of gene expression hint at the possible role of sexually antagonistic selection in having favored suppressed recombination. In total, the genome assembly contained 34,105 expressed genes, of which 10,076 were assigned to linkage groups. There was limited evidence of Y-chromosome degeneration in terms of gene loss and pseudogenization, but sequence divergence between the X and Y copies of many sex-linked genes was higher than between M. annua and its dioecious sister species M. huetii with which it shares a sex-determining region. The Mendelian inheritance of sex in interspecific crosses, combined with the other observed pattern, suggest that the M. annua Y chromosome has at least two evolutionary strata: a small old stratum shared with M. huetii, and a more recent larger stratum that is probably unique to M. annua and that stopped recombining about one million years ago.Article summaryPlants that evolved separate sexes (dioecy) recently are ideal models for studying the early stages of sex-chromosome evolution. Here, we use karyological, whole genome and transcriptome data to characterize the homomorphic sex chromosomes of the annual dioecious plant Mercurialis annua. Our analysis reveals many typical hallmarks of dioecy and sex-chromosome evolution, including sex-biased gene expression and high X/Y sequence divergence, yet few premature stop codons in Y-linked genes and very little outright gene loss, despite 1/3 of the sex chromosome having ceased recombination in males. Our results confirm that the M. annua species complex is a fertile system for probing early stages in the evolution of sex chromosomes.

scholarly journals Y-chromosome haplotypes of varying differentiation to the X are not associated with male fitness in common frogs

2019 ◽  
Author(s):  
Paris Veltsos ◽  
Nicolas Rodrigues ◽  
Tania Studer ◽  
Wen-Juan Ma ◽  
Roberto Sermier ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Chromosome Evolution ◽  
Chromosome Differentiation ◽  
Y Chromosomes ◽  
Male Phenotype ◽  
Xx Males

AbstractThe canonical model of sex-chromosome evolution assigns a key role to sexually antagonistic (SA) genes on the arrest of recombination and ensuing degeneration of Y chromosomes. This assumption cannot be tested in organisms with highly differentiated sex chromosomes, such as mammals or birds, owing to the lack of polymorphism. Fixation of SA alleles, furthermore, might be the consequence rather than the cause of recombination arrest. Here we focus on a population of common frogs (Rana temporaria) where XY males with genetically differentiated Y chromosomes (non-recombinant Y haplotypes) coexist with both XY° males with proto-Y chromosomes (only differentiated from X chromosomes in the immediate vicinity of the candidate sex-determining locus Dmrt1) and XX males with undifferentiated sex chromosomes (genetically identical to XX females). Our study shows no effect of sex-chromosome differentiation on male phenotype, mating success or fathering success. Our conclusions rejoin genomic studies that found no differences in gene expression between XY, XY° and XX males. Sexual dimorphism in common frogs seems to result from the differential expression of autosomal genes rather than sex-linked SA genes. Among-male variance in sex-chromosome differentiation is better explained by a polymorphism in the penetrance of alleles at the sex locus, resulting in variable levels of sex reversal (and thus of X-Y recombination in XY females), independent of sex-linked SA genes.Impact SummaryHumans, like other mammals, present highly differentiated sex chromosomes, with a large, gene-rich X chromosome contrasting with a small, gene-poor Y chromosome. This differentiation results from a process that started approximately 160 Mya, when the Y first stopped recombining with the X. How and why this happened, however, remain controversial. According to the canonical model, the process was initiated by sexually antagonistic selection; namely, selection on the proto-Y chromosome for alleles that were beneficial to males but detrimental to females. The arrest of XY recombination then allowed such alleles to be only transmitted to sons, not to daughters. Although appealing and elegant, this model can no longer be tested in mammals, as it requires a sex-chromosome system at an incipient stage of evolution. Here we focus on a frog that displays within-population polymorphism is sex-chromosome differentiation, where XY males with differentiated chromosomes coexist with XX males lacking Y chromosomes. We find no effect of sex-chromosome differentiation on male phenotype or mating success, opposing expectations from the standard model. Sex linked genes do not seem to have a disproportionate effect on sexual dimorphism. From our results, sexually antagonistic genes show no association with sex-chromosome differentiation in frogs, which calls for alternative models of sex-chromosome evolution.

scholarly journals The effects of haploid selection on Y chromosome evolution in two closely related dioecious plants

2018 ◽  
Author(s):  
George Sandler ◽  
Felix E.G. Beaudry ◽  
Spencer C.H. Barrett ◽  
Stephen I. Wright
Keyword(s):  
Gene Expression ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Chromosome Evolution ◽  
Y Chromosomes ◽  
Expression Bias ◽  
Haploid Selection ◽  
Plant Sex

AbstractThe evolution of sex chromosomes is usually considered to be driven by sexually antagonistic selection in the diploid phase. However, selection during the haploid gametic phase of the lifecycle has recently received theoretical attention as possibly playing a central role in sex chromosome evolution, especially in plants where gene expression in the haploid phase is extensive. In particular, male-specific haploid selection might favour the linkage of pollen beneficial alleles to male sex determining regions on incipient Y chromosomes. This linkage might then allow such alleles to further specialise for the haploid phase. Purifying haploid selection is also expected to slow the degeneration of Y-linked genes expressed in the haploid phase. Here, we examine the evolution of gene expression in flower buds and pollen of two species of Rumex to test for signatures of haploid selection acting during plant sex chromosome evolution. We find that genes with high ancestral pollen expression bias occur more often on sex chromosomes than autosomes and that genes on the Y chromosome are more likely to become enriched for pollen expression bias. We also find that genes with low expression in pollen are more likely to be lost from the Y chromosome. Our results suggest that sex-specific haploid selection during the gametophytic stage of the lifecycle may be a major contributor to several features of plant sex chromosome evolution.

scholarly journals Early Sex-Chromosome Evolution in the Diploid Dioecious Plant Mercurialis annua

Genetics ◽  
2019 ◽  
Vol 212 (3) ◽  
pp. 815-835 ◽  
Author(s):  
Paris Veltsos ◽  
Kate E. Ridout ◽  
Melissa A. Toups ◽  
Santiago C. González-Martínez ◽  
Aline Muyle ◽  
...  
Keyword(s):  
Genetic Mapping ◽  
Y Chromosome ◽  
Sex Chromosomes ◽  
Genome Assembly ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
De Novo ◽  
Sex Chromosome Evolution ◽  
Suppressed Recombination ◽  
Mercurialis Annua

Suppressed recombination allows divergence between homologous sex chromosomes and the functionality of their genes. Here, we reveal patterns of the earliest stages of sex-chromosome evolution in the diploid dioecious herb Mercurialis annua on the basis of cytological analysis, de novo genome assembly and annotation, genetic mapping, exome resequencing of natural populations, and transcriptome analysis. The genome assembly contained 34,105 expressed genes, of which 10,076 were assigned to linkage groups. Genetic mapping and exome resequencing of individuals across the species range both identified the largest linkage group, LG1, as the sex chromosome. Although the sex chromosomes of M. annua are karyotypically homomorphic, we estimate that about one-third of the Y chromosome, containing 568 transcripts and spanning 22.3 cM in the corresponding female map, has ceased recombining. Nevertheless, we found limited evidence for Y-chromosome degeneration in terms of gene loss and pseudogenization, and most X- and Y-linked genes appear to have diverged in the period subsequent to speciation between M. annua and its sister species M. huetii, which shares the same sex-determining region. Taken together, our results suggest that the M. annua Y chromosome has at least two evolutionary strata: a small old stratum shared with M. huetii, and a more recent larger stratum that is probably unique to M. annua and that stopped recombining ∼1 MYA. Patterns of gene expression within the nonrecombining region are consistent with the idea that sexually antagonistic selection may have played a role in favoring suppressed recombination.

scholarly journals Preface

2021 ◽  
Vol 376 (1832) ◽  
pp. 20200088
Author(s):  
Lukáš Kratochvíl ◽  
Matthias Stöck
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Chromosome Evolution ◽  
Evolution Of Sex ◽  
Linkage Groups ◽  
Theme Issue ◽  
Female Heterogamety

This preface introduces the two parts of a theme issue on vertebrate sex chromosome evolution (title below). We invited and edited 22 articles concerning the following main topics (Part 1): sex determination without sex chromosomes and/or governed by epigenetics; origin of sex-determining genes; reasons for differentiation of sex chromosomes and differences in their rates of differentiation as well as (Part 2): co-option of the same linkage groups into sex chromosomes; is differentiation of sex chromosomes a unidirectional pathway?; consequences of differentiated sex chromosomes; differences in differentiation of sex chromosomes under male versus female heterogamety; evolution of sex chromosomes under hybridization and polyploidy. This article is part of the theme issue ‘Challenging the paradigm in sex chromosome evolution: empirical and theoretical insights with a focus on vertebrates (Part I)’.

scholarly journals Genetic and Functional Analysis of DD44, a Sex-Linked Gene From the Dioecious Plant Silene latifolia, Provides Clues to Early Events in Sex Chromosome Evolution

Genetics ◽  
2003 ◽  
Vol 163 (1) ◽  
pp. 321-334 ◽  
Author(s):  
Richard C Moore ◽  
Olga Kozyreva ◽  
Sabine Lebel-Hardenack ◽  
Jiri Siroky ◽  
Roman Hobza ◽  
...  
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Silene Latifolia ◽  
Evolutionary Analysis ◽  
Sex Chromosome Evolution ◽  
Dioecious Plant ◽  
Linked Gene ◽  
Recent Emergence

Abstract Silene latifolia is a dioecious plant with heteromorphic sex chromosomes. The sex chromosomes of S. latifolia provide an opportunity to study the early events in sex chromosome evolution because of their relatively recent emergence. In this article, we present the genetic and physical mapping, expression analysis, and molecular evolutionary analysis of a sex-linked gene from S. latifolia, DD44 (Differential Display 44). DD44 is homologous to the oligomycin sensitivity-conferring protein, an essential component of the mitochondrial ATP synthase, and is ubiquitously expressed in both sexes. We have been able to genetically map DD44 to a region of the Y chromosome that is genetically linked to the carpel-suppressing locus. Although we have physically mapped DD44 to the distal end of the long arm of the X chromosome using fluorescence in situ hybridization (FISH), DD44 maps to the opposite arm of the Y chromosome as determined by our genetic map. These data suggest that chromosomal rearrangements have occurred on the Y chromosome, which may have contributed to the genetic isolation of the Y chromosome. We discuss the implications of these results with respect to the structural and functional evolution of the S. latifolia Y chromosome.

scholarly journals Turtle Insights into the Evolution of the Reptilian Karyotype and the Genomic Architecture of Sex Determination

Genes ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 416 ◽  
Author(s):  
Basanta Bista ◽  
Nicole Valenzuela
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Theoretical Models ◽  
Sex Chromosome Evolution ◽  
Ongoing Research ◽  
Genomic Resources ◽  
Genotypic Sex Determination ◽  
Sex Chromosome System

Sex chromosome evolution remains an evolutionary puzzle despite its importance in understanding sexual development and genome evolution. The seemingly random distribution of sex-determining systems in reptiles offers a unique opportunity to study sex chromosome evolution not afforded by mammals or birds. These reptilian systems derive from multiple transitions in sex determination, some independent, some convergent, that lead to the birth and death of sex chromosomes in various lineages. Here we focus on turtles, an emerging model group with growing genomic resources. We review karyotypic changes that accompanied the evolution of chromosomal systems of genotypic sex determination (GSD) in chelonians from systems under the control of environmental temperature (TSD). These transitions gave rise to 31 GSD species identified thus far (out of 101 turtles with known sex determination), 27 with a characterized sex chromosome system (13 of those karyotypically). These sex chromosomes are varied in terms of the ancestral autosome they co-opted and thus in their homology, as well as in their size (some are macro-, some are micro-chromosomes), heterogamety (some are XX/XY, some ZZ/ZW), dimorphism (some are virtually homomorphic, some heteromorphic with larger-X, larger W, or smaller-Y), age (the oldest system could be ~195 My old and the youngest < 25 My old). Combined, all data indicate that turtles follow some tenets of classic theoretical models of sex chromosome evolution while countering others. Finally, although the study of dosage compensation and molecular divergence of turtle sex chromosomes has lagged behind research on other aspects of their evolution, this gap is rapidly decreasing with the acceleration of ongoing research and growing genomic resources in this group.

scholarly journals Sex determination in the fly Megaselia scalaris, a model system for primary steps of sex chromosome evolution.

Genetics ◽  
1994 ◽  
Vol 136 (3) ◽  
pp. 1097-1104
Author(s):  
W Traut
Keyword(s):  
Y Chromosome ◽  
Sex Chromosomes ◽  
Chromosome Pair ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Random Amplified Polymorphic Dna ◽  
Sex Chromosome Evolution ◽  
Y Chromosomes ◽  
Megaselia Scalaris ◽  
Primary Male

Abstract The fly Megaselia scalaris Loew possesses three homomorphic chromosome pairs; 2 is the sex chromosome pair in two wild-type laboratory stocks of different geographic origin (designated "original" sex chromosome pair in this paper). The primary male-determining function moves at a very low rate to other chromosomes, thereby creating new Y chromosomes. Random amplified polymorphic DNA markers obtained by polymerase chain reaction with single decamer primers and a few available phenotypic markers were used in testcrosses to localize the sex-determining loci and to define the new sex chromosomes. Four cases are presented in which the primary male-determining function had been transferred from the original Y chromosome to a new locus either on one of the autosomes or on the original X chromosome, presumably by transposition. In these cases, the sex-determining function had moved to a different locus without an obvious cotransfer of other Y chromosome markers. Thus, with Megaselia we are afforded an experimental system to study the otherwise hypothetical primary stages of sex chromosome evolution. An initial molecular differentiation is apparent even in the new sex chromosomes. Molecular differences between the original X and Y chromosomes illustrate a slightly more advanced stage of sex chromosome evolution.

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