scholarly journals Algal Sex Determination and the Evolution of Anisogamy

2019 ◽  
Vol 73 (1) ◽  
pp. 267-291 ◽  
Author(s):  
James Umen ◽  
Susana Coelho
Keyword(s):  
Sex Determination ◽  
Sexual Reproduction ◽  
Green Algae ◽  
Life Histories ◽  
Mating Systems ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Photosynthetic Eukaryotes ◽  
Sex Determination Mechanisms ◽  
Shed Light

Algae are photosynthetic eukaryotes whose taxonomic breadth covers a range of life histories, degrees of cellular and developmental complexity, and diverse patterns of sexual reproduction. These patterns include haploid- and diploid-phase sex determination, isogamous mating systems, and dimorphic sexes. Despite the ubiquity of sexual reproduction in algae, their mating-type-determination and sex-determination mechanisms have been investigated in only a limited number of representatives. These include volvocine green algae, where sexual cycles and sex-determining mechanisms have shed light on the transition from mating types to sexes, and brown algae, which are a model for UV sex chromosome evolution in the context of a complex haplodiplontic life cycle. Recent advances in genomics have aided progress in understanding sexual cycles in less-studied taxa including ulvophyte, charophyte, and prasinophyte green algae, as well as in diatoms.

scholarly journals The Diversity and Evolution of Sex Chromosomes in Frogs

Genes ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 483
Author(s):  
Wen-Juan Ma ◽  
Paris Veltsos
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Comparative Genomic ◽  
Ancestral State ◽  
Heteromorphic Sex Chromosomes ◽  
Genomic Studies ◽  
Evolutionary Trajectories ◽  
Heterogametic Sex

Frogs are ideal organisms for studying sex chromosome evolution because of their diversity in sex chromosome differentiation and sex-determination systems. We review 222 anuran frogs, spanning ~220 Myr of divergence, with characterized sex chromosomes, and discuss their evolution, phylogenetic distribution and transitions between homomorphic and heteromorphic states, as well as between sex-determination systems. Most (~75%) anurans have homomorphic sex chromosomes, with XY systems being three times more common than ZW systems. Most remaining anurans (~25%) have heteromorphic sex chromosomes, with XY and ZW systems almost equally represented. There are Y-autosome fusions in 11 species, and no W-/Z-/X-autosome fusions are known. The phylogeny represents at least 19 transitions between sex-determination systems and at least 16 cases of independent evolution of heteromorphic sex chromosomes from homomorphy, the likely ancestral state. Five lineages mostly have heteromorphic sex chromosomes, which might have evolved due to demographic and sexual selection attributes of those lineages. Males do not recombine over most of their genome, regardless of which is the heterogametic sex. Nevertheless, telomere-restricted recombination between ZW chromosomes has evolved at least once. More comparative genomic studies are needed to understand the evolutionary trajectories of sex chromosomes among frog lineages, especially in the ZW systems.

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 Sex determination without sex chromosomes

2021 ◽  
Vol 376 (1832) ◽  
pp. 20200109 ◽  
Author(s):  
Ceri Weber ◽  
Blanche Capel
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Metabolic Pathways ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Alternative Pathway ◽  
Cellular Processes ◽  
Molecular Events ◽  
Effects Of Temperature ◽  
Reptilian Species

With or without sex chromosomes, sex determination is a synthesis of many molecular events that drives a community of cells towards a coordinated tissue fate. In this review, we will consider how a sex determination pathway can be engaged and stabilized without an inherited genetic determinant. In many reptilian species, no sex chromosomes have been identified, yet a conserved network of gene expression is initiated. Recent studies propose that epigenetic regulation mediates the effects of temperature on these genes through dynamic post-transcriptional, post-translational and metabolic pathways. It is likely that there is no singular regulator of sex determination, but rather an accumulation of molecular events that shift the scales towards one fate over another until a threshold is reached sufficient to maintain and stabilize one pathway and repress the alternative pathway. Investigations into the mechanism underlying sex determination without sex chromosomes should focus on cellular processes that are frequently activated by multiple stimuli or can synthesize multiple inputs and drive a coordinated response. 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 The Genome ofArmadillidium vulgare(Crustacea, Isopoda) Provides Insights into Sex Chromosome Evolution in the Context of Cytoplasmic Sex Determination

2019 ◽  
Vol 36 (4) ◽  
pp. 727-741 ◽  
Author(s):  
Mohamed Amine Chebbi ◽  
Thomas Becking ◽  
Bouziane Moumen ◽  
Isabelle Giraud ◽  
Clément Gilbert ◽  
...  
Keyword(s):  
Sex Determination ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Chromosome Evolution

scholarly journals Multi-Tissue Transcriptome Analysis Identifies Key Sexual Development-Related Genes of the Ornate Spiny Lobster (Panulirus ornatus)

Genes ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1150
Author(s):  
Tomer Ventura ◽  
Jennifer C. Chandler ◽  
Tuan V. Nguyen ◽  
Cameron J. Hyde ◽  
Abigail Elizur ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sexual Development ◽  
Molecular Mechanisms ◽  
Sex Chromosome ◽  
Spiny Lobster ◽  
Homology Search ◽  
Previous Knowledge ◽  
Key Factors ◽  
Factors Associated ◽  
Sex Determination Mechanisms

Sexual development involves the successive and overlapping processes of sex determination, sexual differentiation, and ultimately sexual maturation, enabling animals to reproduce. This provides a mechanism for enriched genetic variation which enables populations to withstand ever-changing environments, selecting for adapted individuals and driving speciation. The molecular mechanisms of sexual development display a bewildering diversity, even in closely related taxa. Many sex determination mechanisms across animals include the key family of “doublesex- and male abnormal3-related transcription factors” (Dmrts). In a few exceptional species, a single Dmrt residing on a sex chromosome acts as the master sex regulator. In this study, we provide compelling evidence for this model of sex determination in the ornate spiny lobster Panulius ornatus, concurrent with recent reports in the eastern spiny lobster Sagmariasus verreauxi. Using a multi-tissue transcriptomic database established for P. ornatus, we screened for the key factors associated with sexual development (by homology search and using previous knowledge of these factors from related species), providing an in-depth understanding of sexual development in decapods. Further research has the potential to close significant gaps in our understanding of reproductive development in this ecologically and commercially significant order.

scholarly journals Histone Acetylation and Gene Expression Analysis of Sex lethal Mutants in Drosophila

Genetics ◽  
2000 ◽  
Vol 155 (2) ◽  
pp. 753-763
Author(s):  
Utpal Bhadra ◽  
Manika Pal-Bhadra ◽  
James A Birchler
Keyword(s):  
Gene Expression ◽  
Sex Determination ◽  
Sex Chromosome ◽  
Autosomal Gene ◽  
Single Sex ◽  
Dosage Effects ◽  
Male Specific Lethal ◽  
Sex Lethal ◽  
Male Specific ◽  
Sex Determination Mechanisms

Abstract The evolution of sex determination mechanisms is often accompanied by reduction in dosage of genes on a whole chromosome. Under these circumstances, negatively acting regulatory genes would tend to double the expression of the genome, which produces compensation of the single-sex chromosome and increases autosomal gene expression. Previous work has suggested that to reduce the autosomal expression to the female level, these dosage effects are modified by a chromatin complex specific to males, which sequesters a histone acetylase to the X. The reduced autosomal histone 4 lysine 16 (H4Lys16) acetylation results in lowered autosomal expression, while the higher acetylation on the X is mitigated by the male-specific lethal complex, preventing overexpression. In this report, we examine how mutations in the principal sex determination gene, Sex lethal (Sxl), impact the H4 acetylation and gene expression on both the X and autosomes. When Sxl expression is missing in females, we find that the sequestration occurs concordantly with reductions in autosomal H4Lys16 acetylation and gene expression on the whole. When Sxl is ectopically expressed in SxlM mutant males, the sequestration is disrupted, leading to an increase in autosomal H4Lys16 acetylation and overall gene expression. In both cases we find relatively little effect upon X chromosomal gene expression.

scholarly journals Lizards as Model Organisms of Sex Chromosome Evolution: What We Really Know from A Systematic Distribution of Available Data?

Genes ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1341
Author(s):  
Marcello Mezzasalma ◽  
Fabio M. Guarino ◽  
Gaetano Odierna
Keyword(s):  
Sex Determination ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Sex Reversal ◽  
Model Organisms ◽  
Sex Chromosome Evolution ◽  
Temperature Dependent ◽  
Systematic Assessment ◽  
Qualitative And Quantitative ◽  
Unique Model

Lizards represent unique model organisms in the study of sex determination and sex chromosome evolution. Among tetrapods, they are characterized by an unparalleled diversity of sex determination systems, including temperature-dependent sex determination (TSD) and genetic sex determination (GSD) under either male or female heterogamety. Sex chromosome systems are also extremely variable in lizards. They include simple (XY and ZW) and multiple (X1X2Y and Z1Z2W) sex chromosome systems and encompass all the different hypothesized stages of diversification of heterogametic chromosomes, from homomorphic to heteromorphic and completely heterochromatic sex chromosomes. The co-occurrence of TSD, GSD and different sex chromosome systems also characterizes different lizard taxa, which represent ideal models to study the emergence and the evolutionary drivers of sex reversal and sex chromosome turnover. In this review, we present a synthesis of general genome and karyotype features of non-snakes squamates and discuss the main theories and evidences on the evolution and diversification of their different sex determination and sex chromosome systems. We here provide a systematic assessment of the available data on lizard sex chromosome systems and an overview of the main cytogenetic and molecular methods used for their identification, using a qualitative and quantitative approach.

scholarly journals Sex chromosome evolution, heterochiasmy and physiological QTL in the salmonid Brook Charr Salvelinus fontinalis

2017 ◽  
Author(s):  
Ben J. G. Sutherland ◽  
Ciro Rico ◽  
Céline Audet ◽  
Louis Bernatchez
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Genetic Architecture ◽  
Salvelinus Fontinalis ◽  
Sex Chromosome ◽  
Brook Charr ◽  
Determination System ◽  
Males And Females ◽  
Sex Determination System ◽  
Sex Determination Mechanisms

ABSTRACTWhole genome duplication can have large impacts on genome evolution, and much remains unknown about these impacts. This includes the mechanisms of coping with a duplicated sex determination system and whether this has an impact on increasing the diversity of sex determination mechanisms. Other impacts include sexual conflict, where alleles having different optimums in each sex can result in sequestration of genes into non-recombining sex chromosomes. Sex chromosome development itself may involve sex-specific recombination rate (i.e. heterochiasmy), which is also poorly understood. Family Salmonidae is a model system for these phenomena, having undergone autotetraploidization and subsequent rediploidization in most of the genome at the base of the lineage. The salmonid master sex determining gene is known, and many species have non-homologous sex chromosomes, putatively due to transposition of this gene. In this study, we identify the sex chromosome of Brook Charr Salvelinus fontinalis and compare sex chromosome identities across the lineage (eight species, four genera). Although non-homology is frequent, homologous sex chromosomes and other consistencies are present in distantly related species, indicating probable convergence on specific sex and neo-sex chromosomes. We also characterize strong heterochiasmy with 2.7-fold more crossovers in maternal than paternal haplotypes with paternal crossovers biased to chromosome ends. When considering only rediploidized chromosomes, the overall heterochiasmy trend remains, although with only 1.9-fold more recombination in the female than the male. Y chromosome crossovers are restricted to a single end of the chromosome, and this chromosome contains a large interspecific inversion, although its status between males and females remains unknown. Finally, we identify QTL for 21 unique growth, reproductive and stress-related phenotypes to improve knowledge of the genetic architecture of these traits important to aquaculture and evolution.

scholarly journals Evolution of a sex megachromosome

2020 ◽  
Author(s):  
Matthew A. Conte ◽  
Frances E. Clark ◽  
Reade B. Roberts ◽  
Luohao Xu ◽  
Wenjing Tao ◽  
...  
Keyword(s):  
Sex Determination ◽  
Chromosome Evolution ◽  
Sex Chromosome ◽  
Focal Point ◽  
Alternative Hypothesis ◽  
Cichlid Fish ◽  
B Chromosome ◽  
Sex Chromosome Evolution ◽  
Evolutionary Genomic ◽  
Size And Morphology

AbstractChromosome size and morphology vary within and among species, but little is known about either the proximate or ultimate causes of these differences. Cichlid fish species in the tribe Oreochromini share an unusual megachromosome that is ~3 times longer than any of the other chromosomes. This megachromosome functions as a sex chromosome in some of these species. We explore two hypotheses of how this sex megachromosome may have evolved. The first hypothesis proposes that it developed by the accumulation of repetitive elements as recombination was reduced around a dominant sex-determination locus, as suggested by traditional models of sex chromosome evolution. An alternative hypothesis is that the megachromosome originated via the fusion of an autosome with a highly-repetitive B chromosome, one of which had carried a sex-determination locus. Here we test these hypotheses using comparative analysis of several chromosome-scale cichlid and teleost genomes. We find the megachromosome consists of three distinct regions based on patterns of recombination, gene and transposable element content, and synteny to the ancestral autosome. A WZ sex-determination locus encompasses the last ~105Mbp of the 134Mbp megachromosome and the last 47Mbp of the megachromosome shares no obvious homology to any ancestral chromosome. Comparisons across 69 teleost genomes reveal the megachromosome contains unparalleled amounts of endogenous retroviral elements, immunoglobulin genes, and long non-coding RNAs. Although the origin of this megachromosome remains ambiguous, it has clearly been a focal point of extensive evolutionary genomic conflicts. This megachromosome represents an interesting system for studying sex chromosome evolution and genomic conflicts.

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