Mismatches between the genetic and phenotypic sex in the wild Kou population of Nile tilapia Oreochromis niloticus

Sissao Rokyatou, D'Cotta Helena, Baroiller Jean-François, Toguyeni Aboubacar. 2019. Mismatches between the genetic and phenotypic sex in the wild Kou population of Nile tilapia Oreochromis niloticus. PeerJ, 7:e7709, 26 p.

Quartile : Q2, Sujet : MULTIDISCIPLINARY SCIENCES

Résumé : Sex determination and sex chromosomes can be very diverse between teleost species. The group of tilapias shows a polymorphism in sex determination not only between closely related species but also between domestic strains within a species. In the Nile tilapia, the major effect genes and therefore the Y chromosome have been located on either linkage group 1 (LG1) or LG23 depending on the strains. In a Japanese strain, the sex determinant of LG23 (the amhY gene) has been identified as a duplicated amh (anti-Müllerian hormone) gene, with its gametolog found on the X chromosome (amhX). AmhY is located in tandem with the amhΔY gene (a truncated form) on the Y chromosome. X and Y chromosome markers based on the amh genes have been validated only on a few domestic strains but not in wild populations. Here, we used four of these markers in order to examine (1) the possible variation in sex determination of a wild population of Nile tilapia living in Lake Kou (Burkina Faso), (2) putative polymorphisms for these amh copies and (3) the existence of sex reversed individuals in the wild. Our genotyping of 91 wild Kou individuals with the amh sex-diagnostic markers of LG23 showed that while phenotypic females were all XX, phenotypic males were either XY or XX. Progeny testing of eight of these XX males revealed that one of these males consistently sired all-female progenies, suggesting that it is a wild sex reversed male (which could result from high temperature effects). The other XX males gave balanced sex ratios, suggesting that sex is controlled by another locus (possibly on another LG) which may be epistatically dominant over the LG23 locus. Finally, identification of unexpected amh genotypes was found for two individuals. They produced either balanced or female-biased sex ratios, depending on the breeder with whom they were crossed, suggesting possible recombination between the X and the Y chromosomes.

Mots-clés Agrovoc : Oreochromis niloticus, écologie animale, marqueur génétique, polymorphisme génétique, lac

Mots-clés géographiques Agrovoc : Burkina Faso

Mots-clés libres : Nile tilapia, Sex determination, Sex-reversal, Sex chromosomes, Wild population

Classification Agris : M40 - Écologie aquatique
L10 - Génétique et amélioration des animaux

Champ stratégique Cirad : CTS 1 (2019-) - Biodiversité

Auteurs et affiliations

• Sissao Rokyatou, Université Nazi Boni (BFA) - auteur correspondant
• D'Cotta Helena, CIRAD-PERSYST-UMR ISEM (FRA) ORCID: 0000-0003-2739-3476
• Baroiller Jean-François, CIRAD-PERSYST-UMR ISEM (FRA) ORCID: 0000-0002-0992-1725
• Toguyeni Aboubacar, Université Nazi Boni (BFA)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/594967/)

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