Are there female heterogametic strains of Chironomus tentans Fabricius?

1984 ◽  
Vol 26 (6) ◽  
pp. 743-747 ◽  
Author(s):  
Jon Martin ◽  
B. T. O. Lee
Keyword(s):  
Sex Determination ◽  
Published Data ◽  
Chironomus Tentans ◽  
Adequate Explanation ◽  
Male And Female ◽  
Female Heterogamety ◽  
Male Heterogamety

Although male heterogamety is the generally accepted method of sex determination in Chironomus, female heterogamety has been reported for some strains of Chironomus tentans. Some new data, combined with a reassessment of the published data, indicate that the proposal of female heterogamety rests on inconclusive data, while male heterogamety provides an adequate explanation of sex determination in C. tentans. A cross which would unambiguously discriminate between male and female heterogamety in these strains is proposed, although it is considered unlikely that female heterogamety exists in this species.Key words: sex determination, female heterogamety, Chironomus.

scholarly journals Do male and female heterogamety really differ in expression regulation? Lack of global dosage balance in pygopodid geckos

2021 ◽  
Vol 376 (1833) ◽  
pp. 20200102 ◽  
Author(s):  
Michail Rovatsos ◽  
Tony Gamble ◽  
Stuart V. Nielsen ◽  
Arthur Georges ◽  
Tariq Ezaz ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Gene Dosage ◽  
Regulatory Mechanisms ◽  
Gene Copy ◽  
Male And Female ◽  
Gene Dose ◽  
Female Heterogamety ◽  
Dosage Balance ◽  
Male Heterogamety

Differentiation of sex chromosomes is thought to have evolved with cessation of recombination and subsequent loss of genes from the degenerated partner (Y and W) of sex chromosomes, which in turn leads to imbalance of gene dosage between sexes. Based on work with traditional model species, theory suggests that unequal gene copy numbers lead to the evolution of mechanisms to counter this imbalance. Dosage compensation, or at least achieving dosage balance in expression of sex-linked genes between sexes, has largely been documented in lineages with male heterogamety (XX/XY sex determination), while ZZ/ZW systems are assumed to be usually associated with the lack of chromosome-wide gene dose regulatory mechanisms. Here, we document that although the pygopodid geckos evolved male heterogamety with a degenerated Y chromosome 32–72 Ma, one species in particular, Burton's legless lizard ( Lialis burtonis ), does not possess dosage balance in the expression of genes in its X-specific region. We summarize studies on gene dose regulatory mechanisms in animals and conclude that there is in them no significant dichotomy between male and female heterogamety. We speculate that gene dose regulatory mechanisms are likely to be related to the general mechanisms of sex determination instead of type of heterogamety. 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 II)’.

Do male and female heterogamety really differ in expression regulation? Lack of global dosage balance in pygopodid geckos

2020 ◽  
Author(s):  
Michail Rovatsos ◽  
Tony Gamble ◽  
Stuart V. Nielsen ◽  
Arthur Georges ◽  
Tariq Ezaz ◽  
...  
Keyword(s):  
Sex Determination ◽  
Sex Chromosomes ◽  
Gene Dosage ◽  
Regulatory Mechanisms ◽  
Gene Copy ◽  
Male And Female ◽  
Gene Dose ◽  
Female Heterogamety ◽  
Dosage Balance ◽  
Male Heterogamety

AbstractDifferentiation of sex chromosomes is thought to have evolved with cessation of recombination and subsequent loss of genes from the degenerated partner (Y and W) of sex chromosomes, which in turn leads to imbalance of gene dosage between sexes. Based on work with traditional model species, theory suggests that unequal gene copy numbers lead to the evolution of mechanisms to counter this imbalance. Dosage compensation, or at least achieving dosage balance in expression of sex-linked genes between sexes, has largely been documented in lineages with male heterogamety (XX/XY sex determination), while ZZ/ZW systems are assumed to be usually associated with the lack of chromosome-wide gene dose regulatory mechanisms. Here we document that although the pygopodid geckos evolved male heterogamety with a degenerated Y chromosome 32-72 million years ago, one species in particular, Burton’s legless lizard (Lialis burtonis), does not possess dosage balance in the expression of genes in its X-specific region. We summarize studies on gene dose regulatory mechanisms in animals and conclude that there is in them no significant dichotomy between male and female heterogamety. We speculate that gene dose regulatory mechanisms are likely to be related to the general mechanisms of sex determination instead of type of heterogamety.

MALE AND FEMALE HETEROGAMETY IN POPULATIONS OF CHIRONOMUS TENTANS (DIPTERA: CHIRONOMIDAE)

1971 ◽  
Vol 103 (3) ◽  
pp. 369-372 ◽  
Author(s):  
Peter E. Thompson
Keyword(s):  
Sex Determination ◽  
Chromosome 1 ◽  
Chironomus Tentans ◽  
Male And Female ◽  
Dominance Relations ◽  
Female Heterogamety ◽  
The Right

AbstractPopulations of Chironomus tentans from Iowa and Wisconsin show consistent polymorphisms for inversion sequences of chromosome 1 which are associated with sex. Male larvae from Iowa populations are invariably heterozygous for a sequence of the left arm which is never present in females. In a Wisconsin population, however, females are consistently heterozygous for a dominant sex factor, female determiner (Fd), linked to but not inseparable from an inversion sequence of the right arm. Two primary loci for sex determination appear to have evolved different dominance relations in these races.

Weak male-determining genes and female heterogamety in Chironomus tentans

1984 ◽  
Vol 26 (6) ◽  
pp. 748-751
Author(s):  
Ray Feraday
Keyword(s):  
Sex Determination ◽  
Sex Chromosome ◽  
Chironomus Tentans ◽  
Female Development ◽  
Female Heterogamety ◽  
Dominant Female

Female heterogamety in the midge Chironomus tentans has been previously reported and attributed to a dominant female determiner. Published results are not consistent with the interpretation, and the female heterogamety, if any, can be better explained by a model involving a weakened male determiner. Suggestions are made for crosses between populations with different sex-determining mechanisms that would discriminate between models for the evolution of female heterogamety, and serve to determine whether indeed female development is the norm in the absence of any parental sex chromosomes.Key words: Chironomus, heterogamety, sex determination, sex chromosome.

scholarly journals Evolution of sex determination and heterogamety changes in section Otites of the genus Silene

2018 ◽  
Author(s):  
Veronika Balounova, ◽  
Roman Gogela ◽  
Radim Cegan ◽  
Patrik Cangren ◽  
Jitka Zluvova ◽  
...  
Keyword(s):  
Phylogenetic Analysis ◽  
Sex Determination ◽  
Sex Chromosome ◽  
The Other ◽  
Close Relative ◽  
Sequence Analyses ◽  
Female Heterogamety ◽  
Genus Silene ◽  
Plant Sex ◽  
Male Heterogamety

AbstractSwitches in heterogamety occasionally occur both in animals and plants, although plant sex determination systems are mostly more recently evolved than those of animals, and have had less time for switches to occur. However, our previous research revealed a switch in heterogamety in section Otites of the plant genus Silene.Here we analyse in detail the evolution of genetic sex determination in section Otites, which is estimated to have evolved about 0.55 MYA. Our study confirms female heterogamety in S. otites and newly reveals female heterogamety in S. borysthenica. Sequence analyses and genetic mapping show that the sex-linked regions of these two species are the same, but the region in S. colpophylla, a close relative with male heterogamety, is different. The sex chromosome pairs of S. colpophylla and S. otites each correspond to an autosome of the other species, and both differ from the XY pair in S. latifolia, in a different section of the genus. Our phylogenetic analysis suggests a possible change from female to male heterogamety within Silene section Otites, making these species suitable for detailed studies of the events involved.

scholarly journals The Sex Determination Cascade in the Silkworm

Genes ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 315
Author(s):  
Xu Yang ◽  
Kai Chen ◽  
Yaohui Wang ◽  
Dehong Yang ◽  
Yongping Huang
Keyword(s):  
Sex Determination ◽  
Molecular Mechanisms ◽  
Future Research ◽  
Model Species ◽  
Male And Female ◽  
Master Regulators ◽  
Primary Signal ◽  
Basic Understanding ◽  
Female Specific ◽  
Working Mechanisms

In insects, sex determination pathways involve three levels of master regulators: primary signals, which determine the sex; executors, which control sex-specific differentiation of tissues and organs; and transducers, which link the primary signals to the executors. The primary signals differ widely among insect species. In Diptera alone, several unrelated primary sex determiners have been identified. However, the doublesex (dsx) gene is highly conserved as the executor component across multiple insect orders. The transducer level shows an intermediate level of conservation. In many, but not all examined insects, a key transducer role is performed by transformer (tra), which controls sex-specific splicing of dsx. In Lepidoptera, studies of sex determination have focused on the lepidopteran model species Bombyx mori (the silkworm). In B. mori, the primary signal of sex determination cascade starts from Fem, a female-specific PIWI-interacting RNA, and its targeting gene Masc, which is apparently specific to and conserved among Lepidoptera. Tra has not been found in Lepidoptera. Instead, the B. mori PSI protein binds directly to dsx pre-mRNA and regulates its alternative splicing to produce male- and female-specific transcripts. Despite this basic understanding of the molecular mechanisms underlying sex determination, the links among the primary signals, transducers and executors remain largely unknown in Lepidoptera. In this review, we focus on the latest findings regarding the functions and working mechanisms of genes involved in feminization and masculinization in Lepidoptera and discuss directions for future research of sex determination in the silkworm.

Gene networks underlying functional sex in Sparidae (Pisces, Teleostei)

2018 ◽  
Author(s):  
Αλέξανδρος Τσακογιάννης
Keyword(s):  
Gene Expression ◽  
Sex Determination ◽  
Gene Networks ◽  
Expression Patterns ◽  
Gene Families ◽  
Male And Female ◽  
Dentex Dentex ◽  
The Common ◽  
Model Fish Species ◽  
Model Fish

The differences between sexes and the concept of sex determination have always fascinated, yet troubled philosophers and scientists. Among the animals that reproduce sexually, teleost fishes show a very wide repertoire of reproductive modes. Except for the gonochoristic species, fish are the only vertebrates in which hermaphroditism appears naturally. Hermaphroditism refers to the capability of an organism to reproduce both as male and female in its life cycle and there are various forms of it. In sequential hermaphroditism, an individual begins as female first and then can change sex to become male (protogyny), or vice versa (protandry). The diverse sex-phenotypes of fish are regulated by a variety of sex determination mechanisms, along a continuum of environmental and heritable factors. The vast majority of sexually dimorphic traits result from the differential expression of genes that are present in both sexes. To date, studies regarding the sex-specific differences in gene expression have been conducted mainly in sex determination systems of model fish species that are well characterized at the genomic level, with distinguishable heteromorphic sex chromosomes, exhibiting genetic sex determination and gonochorism. Among teleosts, the Sparidae family is considered to be one of the most diversified families regarding its reproductive systems, and thus is a unique model for comparative studies to understand the molecular mechanisms underlying different sexual motifs. In this study, using RNA sequencing, we studied the transcriptome from gonads and brains of both sexes in five sparid species, representatives of four different reproductive styles. Specifically, we explored the sex-specific expression patterns of a gonochoristic species: the common dentex Dentex dentex, two protogynous hermaphrodites: the red porgy Pagrus pagrus and the common pandora Pagellus erythrinus, the rudimentary hermaphrodite sharpsnout seabream Diplodus puntazzo, and the protandrous gilthead seabream Sparus aurata. We found minor sex-related expression differences indicating a more homogeneous and sexually plastic brain, whereas there was a plethora of sex biased gene expression in the gonads. The functional divergence of the two gonadal types is reflected in their transcriptomic profiles, in terms of the number of genes differentially expressed, as well as the expression magnitude (i.e. fold-change differences). The observation of almost double the number of up-regulated genes in males compared to females indicates a male-biased expression tendency. Focusing on the pathways and genes implicated in sex determination/differentiation, we aimed to unveil the molecular pathways through which these non-model fish species develop a masculine or a feminine character. We observed the implicated pathways and major gene families (e.g. Wnt/b-catenin pathway and Retinoic-acid signaling pathway, Notch, TGFβ) behind sex-biased expression and the recruitment of known sex-related genes either to male or female type of gonads in these fish. (e.g Dmrt1, Sox9, Sox3, Cyp19a, Filgla, Ctnnb1, Gsdf9, Stra6 etc.). We also carefully investigated the presence of genes reported to be involved in sex determination/differentiation mechanisms in other vertebrates and fish and compared their expression patterns in the species under study. The expression profiling exposed known candidate molecular-players/genes establishing the common female (Cyp19a1, Sox3, Figla, Gdf9, Cyp26a, Ctnnb1, Dnmt1, Stra6) and male identity (Dmrt1, Sox9, Dnmt3aa, Rarb, Raraa, Hdac8, Tdrd7) of the gonad in these sparids. Additionally, we focused on those contributing to a species-specific manner either to female (Wnt4a, Dmrt2a, Foxl2 etc.) or to male (Amh, Dmrt3a, Cyp11b etc.) characters, and discussed the expression patterns of factors that belong to important pathways and/or gene families in the SD context, in our species gonadal transcriptomes. Taken together, most of the studied genes form part of the cascade of sex determination, differentiation, and reproduction across teleosts. In this study, we focused on genes that are active when sex is established (sex-maintainers), revealing the basic “gene-toolkit” & gene-networks underlying functional sex in these five sparids. Comparing related species with alternative reproductive styles, we saw different combinations of genes with conserved sex-linked roles and some “handy” molecular players, in a “partially- conserved” or “modulated” network formulating the male and female phenotype. The knowledge obtained in this study and tools developed during the process have set the groundwork for future experiments that can improve the sex control of this species and help the in-deep understanding the complex process of sex differentiation in the more flexible multi-component systems as these studied here.

scholarly journals Drift-Induced Selection Between Male and Female Heterogamety

Genetics ◽  
2017 ◽  
pp. genetics.300151.2017 ◽  
Author(s):  
Carl Veller ◽  
Pavitra Muralidhar ◽  
George W. A. Constable ◽  
Martin A. Nowak
Keyword(s):  
Male And Female ◽  
Female Heterogamety

SEX AND SUPERNUMERARY CHROMOSOMES IN THE DIOECIOUS GRASS SOHNSIA FILIFOLIA

1972 ◽  
Vol 14 (1) ◽  
pp. 175-180 ◽  
Author(s):  
D. N. Singh
Keyword(s):  
Sex Determination ◽  
Y Chromosome ◽  
Supernumerary Chromosome ◽  
The Other ◽  
Male Plant ◽  
Diploid Male ◽  
Male And Female ◽  
Supernumerary Chromosomes ◽  
Determination System ◽  
Sex Determination System

A dioecious grass Sohnsia filifolia (Fourn.) Airy Shaw (Syn. Calamochloa filifolia Fourn.) from Mexico has been found to have 2n = 20 chromosomes in both male and female plants. The staminate plants have one chromosome much longer than the other chromosomes of the complement. One pistillate plant was found to have 30 chromosomes, among which the largest chromosome is quite similar to the largest component of the diploid male plant. The longest chromosome has been designated as the Y chromosome. An XY-mechanism of the Drosophilia type has been suggested for the sex determination system in this species. One small supernumerary chromosome was observed in the microsporocytes of some male plants, but was absent in roots.

Sign in / Sign up

Export Citation Format

Share Document