Maintenance of Ancestral Sex Chromosomes in Palearctic Tree Frogs: Direct Evidence from Hyla orientalis

2013 ◽  
Vol 7 (5) ◽  
pp. 261-266 ◽  
Author(s):  
M. Stöck ◽  
R. Savary ◽  
A. Zaborowska ◽  
G. Górecki ◽  
A. Brelsford ◽  
...  
Keyword(s):  
Sex Chromosomes ◽  
Direct Evidence ◽  
Tree Frogs

scholarly journals Ever-Young Sex Chromosomes in European Tree Frogs

PLoS Biology ◽  
2011 ◽  
Vol 9 (5) ◽  
pp. e1001062 ◽  
Author(s):  
Matthias Stöck ◽  
Agnès Horn ◽  
Christine Grossen ◽  
Dorothea Lindtke ◽  
Roberto Sermier ◽  
...  
Keyword(s):  
Sex Chromosomes ◽  
Tree Frogs

scholarly journals Extreme heterochiasmy and nascent sex chromosomes in European tree frogs

2008 ◽  
Vol 275 (1642) ◽  
pp. 1577-1585 ◽  
Author(s):  
Laura Berset-Brändli ◽  
Julie Jaquiéry ◽  
Thomas Broquet ◽  
Yuko Ulrich ◽  
Nicolas Perrin
Keyword(s):  
Sex Chromosomes ◽  
Tree Frogs

scholarly journals Coexistence of Y, W, and Z sex chromosomes in Xenopus tropicalis

2015 ◽  
Vol 112 (34) ◽  
pp. E4752-E4761 ◽  
Author(s):  
Álvaro S. Roco ◽  
Allen W. Olmstead ◽  
Sigmund J. Degitz ◽  
Tosikazu Amano ◽  
Lyle B. Zimmerman ◽  
...  
Keyword(s):  
Sex Chromosomes ◽  
Direct Evidence ◽  
Sex Chromosome ◽  
Xenopus Tropicalis ◽  
Relevant Model ◽  
Recent Interest ◽  
Different Types ◽  
Sex Chromosome System ◽  
Heterogametic Sex ◽  
System Operating

Homomorphic sex chromosomes and rapid turnover of sex-determining genes can complicate establishing the sex chromosome system operating in a given species. This difficulty exists in Xenopus tropicalis, an anuran quickly becoming a relevant model for genetic, genomic, biochemical, and ecotoxicological research. Despite the recent interest attracted by this species, little is known about its sex chromosome system. Direct evidence that females are the heterogametic sex, as in the related species Xenopus laevis, has yet to be presented. Furthermore, X. laevis’ sex-determining gene, DM-W, does not exist in X. tropicalis, and the sex chromosomes in the two species are not homologous. Here we identify X. tropicalis’ sex chromosome system by integrating data from (i) breeding sex-reversed individuals, (ii) gynogenesis, (iii) triploids, and (iv) crosses among several strains. Our results indicate that at least three different types of sex chromosomes exist: Y, W, and Z, observed in YZ, YW, and ZZ males and in ZW and WW females. Because some combinations of parental sex chromosomes produce unisex offspring and other distorted sex ratios, understanding the sex-determination systems in X. tropicalis is critical for developing this flexible animal model for genetics and ecotoxicology.

scholarly journals When Sex Chromosomes Recombine Only in the Heterogametic Sex: Heterochiasmy and Heterogamety in Hyla Tree Frogs

2020 ◽  
Vol 38 (1) ◽  
pp. 192-200 ◽  
Author(s):  
Christophe Dufresnes ◽  
Alan Brelsford ◽  
Felix Baier ◽  
Nicolas Perrin
Keyword(s):  
Sex Chromosomes ◽  
Deleterious Mutations ◽  
Typical Pattern ◽  
Male Recombination ◽  
Y Chromosomes ◽  
Tree Frogs ◽  
Heterogametic Sex ◽  
Low Rate ◽  
Sex Asymmetry

Abstract Sex chromosomes are classically predicted to stop recombining in the heterogametic sex, thereby enforcing linkage between sex-determining (SD) and sex-antagonistic (SA) genes. With the same rationale, a pre-existing sex asymmetry in recombination is expected to affect the evolution of heterogamety, for example, a low rate of male recombination might favor transitions to XY systems, by generating immediate linkage between SD and SA genes. Furthermore, the accumulation of deleterious mutations on nonrecombining Y chromosomes should favor XY-to-XY transitions (which discard the decayed Y), but disfavor XY-to-ZW transitions (which fix the decayed Y as an autosome). Like many anuran amphibians, Hyla tree frogs have been shown to display drastic heterochiasmy (males only recombine at chromosome tips) and are typically XY, which seems to fit the above expectations. Instead, here we demonstrate that two species, H. sarda and H. savignyi, share a common ZW system since at least 11 Ma. Surprisingly, the typical pattern of restricted male recombination has been maintained since then, despite female heterogamety. Hence, sex chromosomes recombine freely in ZW females, not in ZZ males. This suggests that heterochiasmy does not constrain heterogamety (and vice versa), and that the role of SA genes in the evolution of sex chromosomes might have been overemphasized.

The Immuno-Electron Microscopic Localization of the Mo-Fe Protein Component of Nitrogenase in Cells of Azotobacter Vinelandii

1973 ◽  
Vol 31 ◽  
pp. 574-575
Author(s):  
J. T. Stasny ◽  
R. C. Burns ◽  
R. W. F. Hardy
Keyword(s):  
Cellular Localization ◽  
Direct Evidence ◽  
Azotobacter Vinelandii ◽  
Intracellular Localization ◽  
Protein Component ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Fe Protein ◽  
Intracytoplasmic Membranes

Structure-functlon studies of biological N2-fixation have correlated the presence of the enzyme nitrogenase with increased numbers of intracytoplasmic membranes in Azotobacter. However no direct evidence has been provided for the internal cellular localization of any nitrogenase. Recent advances concerned with the crystallizatiorTand the electron microscopic characterization of the Mo-Fe protein component of Azotobacter nitrogenase, prompted the use of this purified protein to obtain antibodies (Ab) to be conjugated to electron dense markers for the intracellular localization of the protein by electron microscopy. The present study describes the use of ferritin conjugated to goat antitMo-Fe protein immunoglobulin (IgG) and the observations following its topical application to thin sections of N2-grown Azotobacter.

Structural similarity of ribosomes from E. coli and A. salina

1978 ◽  
Vol 36 (2) ◽  
pp. 242-243
Author(s):  
M. Boublik ◽  
R.M. Wydro ◽  
W. Hellmann ◽  
F. Jenkins
Keyword(s):  
Ribosomal Proteins ◽  
Direct Evidence ◽  
Structural Similarity ◽  
Carbon Support ◽  
Artemia Salina ◽  
Uranyl Acetate ◽  
Biological Assays ◽  
E Coli ◽  
And Function ◽  
Fine Carbon

Ribosomes are ribonucleoprotein particles necessary for processing the genetic information of mRNA into proteins. Analogy in composition and function of ribosomes from diverse species, established by biochemical and biological assays, implies their structural similarity. Direct evidence obtained by electron microscopy seems to be of increasing relevance in understanding the structure of ribosomes and the mechanism of their role in protein synthesis.The extent of the structural homology between prokaryotic and eukaryotic ribosomes has been studied on ribosomes of Escherichia coli (E.c.) and Artemia salina (A.s.). Despite the established differences in size and in the amount and proportion of ribosomal proteins and RNAs both types of ribosomes show an overall similarity. The monosomes (stained with 0.5% aqueous uranyl acetate and deposited on a fine carbon support) appear in the electron micrographs as round particles with a diameter of approximately 225Å for the 70S E.c. (Fig. 1) and 260Å for the 80S A.s. monosome (Fig. 2).

Sign in / Sign up

Export Citation Format

Share Document