Sox5 is involved in germ-cell regulation and sex determination in medaka following co-option of nested transposable elements

et al. 2020

Sci Rep

Self Cite

Amphibians evolved in the Devonian period about 400 Mya and represent a transition step in tetrapod evolution. Among amphibians, high-throughput sequencing data are very limited for Caudata, due to their largest genome sizes among terrestrial vertebrates. in this paper we present the transcriptome from the fire bellied newt Cynops orientalis. Data here presented display a high level of completeness, comparable to the fully sequenced genomes available from other amphibians. Moreover, this work focused on genes involved in gametogenesis and sexual development. Surprisingly, the gsdf gene was identified for the first time in a tetrapod species, so far known only from bony fish and basal sarcopterygians. our analysis failed to isolate fgf24 and foxl3, supporting the possible loss of both genes in the common ancestor of Rhipidistians. in Cynops, the expression analysis of genes described to be sex-related in vertebrates singled out an expected functional role for some genes, while others displayed an unforeseen behavior, confirming the high variability of the sex-related pathway in vertebrates. Amphibians represent a group of vertebrates containing over 7,100 species worldwide 1. These organisms evolved in the Devonian period about 400 Mya and represent a transition step in tetrapod evolution 2. Modern-day amphibians have diverged into three orders with distinct anatomical features: Gymnophiona (caecilians, limbless amphibians), Caudata (salamanders and tritons), and Anura (frogs and toads). Amphibians have many features that make them ideal as animal models because of their physiology, diversity, phylogeny, and amazing capability of tissue regeneration. On the other hand, amphibians represent a case of global biodiversity crisis since they are among the most threatened species in the world 3. The Chinese fire-bellied newt, Cynops orientalis (David, 1873), is a small (6-10.3 cm long) urodele (Salamandridae: Pleurodelinae) distributed in Asia. It shows a color ranging from dark brown to black on the back and with belly from orange to scarlet red with numerous black spots. The sexual dimorphism is evident in size (males are smaller than females) and shape of tail and cloaca. C. orientalis lives in ponds and marshes and prefers cold and calm waters with a bottom of mud. In nature, in the Chinese region of Changsha, the reproduction period spans from March to July, when water temperatures range from 15 to 23 °C, and juveniles reach sexual maturity from 1 to 3 years. Data obtained by whole genome sequencing (WGS) are a very valuable resource to understand the evolutionary history and biology of species. Despite the importance of amphibians, the genomes of only 13 species have

Section: Growth Factorcontrasting

confidence: 74%

Section: Growth Factormentioning

confidence: 99%

The transcriptome of the newt Cynops orientalis provides new insights into evolution and function of sexual gene networks in sarcopterygians

Biscotti

Carducci

et al. 2020

Sci Rep

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“…2003 ), it is the master male sex determining gene in the fish Oryzias dancena ( Takehana 2014 ). sox5 , pertaining to the subfamily D, is a regulator of male germ cells in medaka ( Schartl et al. 2018 ).…”

Section: Resultsmentioning

confidence: 99%

A Comparative View on Sex Differentiation and Gametogenesis Genes in Lungfish and Coelacanths

Biscotti

Adolfi

Genome Biology and Evolution

et al. 2018

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Gonadal sex differentiation and reproduction are the keys to the perpetuation of favorable gene combinations and positively selected traits. In vertebrates, several gonad development features that differentiate tetrapods and fishes are likely to be, at least in part, related to the water-to-land transition. The collection of information from basal sarcopterygians, coelacanths, and lungfishes, is crucial to improve our understanding of the molecular evolution of pathways involved in reproductive functions, since these organisms are generally regarded as “living fossils” and as the direct ancestors of tetrapods. Here, we report for the first time the characterization of >50 genes related to sex differentiation and gametogenesis in Latimeria menadoensis and Protopterus annectens. Although the expression profiles of most genes is consistent with the intermediate position of basal sarcopterygians between actinopterygian fish and tetrapods, their phylogenetic placement and presence/absence patterns often reveal a closer affinity to the tetrapod orthologs. On the other hand, particular genes, for example, the male gonad factor gsdf (Gonadal Soma-Derived Factor), provide examples of ancestral traits shared with actinopterygians, which disappeared in the tetrapod lineage.

“…A clear example of TE control in a germline through cis -regulation was reported in the medaka, Oryzias latipes : a LINE/Rex1 retroelement was found within the nonautonomous P element Izanagi , corresponding to the upstream region of the master sex-determining gene ( dmrt1bY ) in medaka. In particular, the LINE/Rex1 -derived sequence located within the Izanagi element carries the binding site for Sox5, a transcriptional factor involved in the regulation of dmrt1bY [ 201 , 202 ]. A role of TEs in the determination of sex chromosome structure and evolution has also been observed in X. maculatus, in which the accumulation and spreading of Texim genes in only the Y chromosome is due to the activity of Helitron transposons, deeply influencing the evolution of this chromosome in platyfish [ 203 ].…”

Section: Tes and Sex Chromosomesmentioning

confidence: 99%

Mobile Elements in Ray-Finned Fish Genomes

Carducci

Canapa

et al. 2020

Life

Ray-finned fishes (Actinopterygii) are a very diverse group of vertebrates, encompassing species adapted to live in freshwater and marine environments, from the deep sea to high mountain streams. Genome sequencing offers a genetic resource for investigating the molecular bases of this phenotypic diversity and these adaptations to various habitats. The wide range of genome sizes observed in fishes is due to the role of transposable elements (TEs), which are powerful drivers of species diversity. Analyses performed to date provide evidence that class II DNA transposons are the most abundant component in most fish genomes and that compared to other vertebrate genomes, many TE superfamilies are present in actinopterygians. Moreover, specific TEs have been reported in ray-finned fishes as a possible result of an intricate relationship between TE evolution and the environment. The data summarized here underline the biological interest in Actinopterygii as a model group to investigate the mechanisms responsible for the high biodiversity observed in this taxon.