Identification of a new repetitive element in the sex chromosomes of <i>Leporinus elongatus</i> (Teleostei: Characiformes: Anostomidae): new insights into the sex chromosomes of <i>Leporinus</i>

Abstract

Leporinuselongatus represents an interesting model for studies on chromosome evolution since it possesses a conspicuous ZZ/ZW sex chromosome system that has been characterized mainly by basic cytogenetic techniques. In the present study we describe a dispersed repetitive element (named LeSpeI) related to the sex chromosomes of L.elongatus. Females revealed clusters of LeSpeI on the long arm of the W chromosome and in the acrocentric NOR-bearing chromosome pair. In males, the signal was restricted to the pericentromeric region of the NOR-bearing chromosomes. Considering the results obtained in the present study using FISH, NOR and C-banding, together with findings from previous studies, it can be inferred that the sex chromosome system of L. elongatus is still undergoing an evolutionary process. The data suggest novelties in relation to the sex chromosomes of the genus Leporinus with the description of a multiple sex chromosome system involving the NOR-bearing chromosomes. Therefore, it is hypothesized that the simple ZW chromosome system previously described for L. elongatus rather is a multiple Z₁Z₁Z₂Z₂/Z₁W₁Z₂W₂ system.

The Birds and the Bees and the Flowers and the Trees: Lessons from Genetic Mapping of Sex Determination in Plants and Animals

“…Among fish whose genomes have been sequenced, the pufferfish (Takifugu rubripes, order Tetraodontiformes) has a male-heterozygous region (Kikuchi et al 2007). In the zebrafish (Danio rerio, Cypriniformes), sex is determined by a combination of genetic and environmental influences (Siegfried and Nusslein-Volhard 2008), while among its relatives, the goldfish has an XY system of GSD (Zhang and Wu 1985) and Leporinus (Characiformes) has a strongly heteromorphic ZW system, with largely heterochromatic W chromosomes, which have probably undergone W-autosome translocations (Parise-Maltempi et al 2007). …”

Sex chromosome composition revealed in Characidium fishes (Characiformes: Crenuchidae) by molecular cytogenetic methods

“…clear correlation between these sequences and sex chromosomes has been established by numerous studies (e.g., Nanda et al 1990Nanda et al , 2000Matsubara et al 2006;Kejnovsky et al 2009) including several Neotropical fish groups (e.g., Parise-Maltempi et al 2007;Cioffi et al 2011Cioffi et al , 2012Machado et al 2011), suggesting that the differentiation of sex chromosomes' mechanism is often associated with the accumulation of repetitive DNA. Accordingly, repetitive sequences represent a powerful tool to elucidate both the processes of morphological differentiation of sex chromosomes in fishes and to possibly understand some of the diversity of the differentiation systems observed in this group of vertebrates (Cioffi et al 2011).…”

“…Fishes, however, express all possible forms of sex determination systems somehow associated with the huge biodiversity levels observed among them (reviewed in Volff et al 2007). In the particular case of Neotropical fishes, female heterogamety was reported in Characidium Reinhardt, 1867 and Parodon genera Valenciennes, 1850 (e.g., Vicente et al 2003;Vicari et al 2008;Machado et al 2011), male heterogamety was found in, e.g., Hoplias malabaricus (Bloch, 1794) (Cioffi et al 2011(Cioffi et al , 2012, and other species have multiple sex chromosomes, such as Leporinus elongatus Valenciennes, 1850 (Parise-Maltempi et al 2007) or Harttia carvalhoi Miranda Ribeiro, 1939 (Cioffi et al 2012) among others. Despite the differences in sex chromosome determination, these chromosomes share some features: Y and W are mostly heterochromatic while X and Z usually have more euchromatic regions.…”

“…gomesi Travassos, 1956 has clearly differentiated Z and W chromosomes, with heterochromatin occupying most of the W chromosome but only the pericentromeric region of the Z chromosome, becoming easily distinguishable from the autosomes (Vicari et al 2008;Pansonato-Alves et al 2011;Machado et al 2011). While heterochromatin is known to be rich in repetitive DNA (e.g., Charlesworth et al 2005;Volff et al 2007), the identification and characterization of repetitive DNAs specific to sex chromosomes has also been performed in fishes (Parise-Maltempi et al 2007;Takehana et al 2012). However, no known function has been attributed to these sequences in fishes or in any other group of organisms where they were described.…”

Estudos citogenéticos no genêro Characidium (Teleostei, Characiformes, Chrenuchidae), com análise estrutural e molecular do sistema ZZ-ZW de cromossomos sexuais

“…Considerando que o DNA satélite consiste em repetições em tandem que geralmente estão localizadas em regiões cromossômicas com conhecidas restrições a recombinação, como regiões pericentroméricas (Oliveira e Wright, 1998), regiões adjacentes ao DNAr 5S (Martins et al, 2006), regiões periteloméricas (Saito et al, 2007) e em cromossomos sexuais e B (Reed e Phillips, 1995;Mandrioli et al, 2003;Parise-Maltempi et al, 2007), pode-se supor que a significativa variabilidade cariotípica observada em populações de C. cf. gomesi da bacia do rio Tietê esteja diretamente relacionada a uma elevada taxa de mutação cromossômica principalmente nestas regiões, bem como a alguns aspectos relacionados ao hábito de vida da espécie e à geografia da região da Cuesta de Botucatu, que facilitariam a fixação de populações apresentando novas variantes cromossômicas.…”