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Sex determination in the Squalius alburnoides complex: an initial characterization of sex cascade elements in the context of a hybrid polyploid genome.

Pala I, Schartl M, Thorsteinsdóttir S, Coelho MM - PLoS ONE (2009)

Bottom Line: Dmrt1 and wt1 transcripts were found at early stages of male development in S. alburnoides and are most likely implicated in the process of gonad development.For the first time in the study of this hybrid complex, it was possible to directly compare the gene expression patterns between the bisexual parental species and the various hybrid forms, for an extended set of genes.The contribution of these genes to gonad integrity maintenance and functionality is apparently unaltered in the hybrids, suggesting that no abrupt shifts in gene expression occurred as a result of hybridisation.

View Article: PubMed Central - PubMed

Affiliation: Centro de Biologia Ambiental, Departamento de Biologia Animal, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal. iapala@fc.ul.pt

ABSTRACT

Background: Sex determination processes vary widely among different vertebrate taxa, but no group offers as much diversity for the study of the evolution of sex determination as teleost fish. However, the knowledge about sex determination gene cascades is scarce in this species-rich group and further difficulties arise when considering hybrid fish taxa, in which mechanisms exhibited by parental species are often disrupted. Even though hybridisation is frequent among teleosts, gene based approaches on sex determination have seldom been conducted in hybrid fish. The hybrid polyploid complex of Squalius alburnoides was used as a model to address this question.

Methodology/principal findings: We have initiated the isolation and characterization of regulatory elements (dmrt1, wt1, dax1 and figla) potentially involved in sex determination in S. alburnoides and in the parental species S. pyrenaicus and analysed their expression patterns by in situ hybridisation. In adults, an overall conservation in the cellular localization of the gene transcripts was observed between the hybrids and parental species. Some novel features emerged, such as dmrt1 expression in adult ovaries, and the non-dimorphic expression of figla, an ovarian marker in other species, in gonads of both sexes in S. alburnoides and S. pyrenaicus. The potential contribution of each gene to the sex determination process was assessed based on the timing and location of expression. Dmrt1 and wt1 transcripts were found at early stages of male development in S. alburnoides and are most likely implicated in the process of gonad development.

Conclusions/significance: For the first time in the study of this hybrid complex, it was possible to directly compare the gene expression patterns between the bisexual parental species and the various hybrid forms, for an extended set of genes. The contribution of these genes to gonad integrity maintenance and functionality is apparently unaltered in the hybrids, suggesting that no abrupt shifts in gene expression occurred as a result of hybridisation.

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Unrooted Neighbour-Joining tree obtained among the FIGLA family of proteins.Dre-FIGLA- Danio rerio, Tni-FIGLA- Tetraodon nigroviridis, Kma-FIGLA- Kryptolebias marmoratus, Hsa- FIGLA- Homo sapiens, Rno-FIGLA- Rattus norvegicus, and Xtr FIGLA- Xenopus (Silurana) tropicalis. Bootstrap values are shown above the branches. ▴ S. pyrenaicus males (PP-M); ▵ females (PP-F) and • S. alburnoides (AA).
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pone-0006401-g004: Unrooted Neighbour-Joining tree obtained among the FIGLA family of proteins.Dre-FIGLA- Danio rerio, Tni-FIGLA- Tetraodon nigroviridis, Kma-FIGLA- Kryptolebias marmoratus, Hsa- FIGLA- Homo sapiens, Rno-FIGLA- Rattus norvegicus, and Xtr FIGLA- Xenopus (Silurana) tropicalis. Bootstrap values are shown above the branches. ▴ S. pyrenaicus males (PP-M); ▵ females (PP-F) and • S. alburnoides (AA).

Mentions: Fragments of approximately 300 bp corresponding to a putative figla product were obtained using S. alburnoides (AA) and S.pyrenaicus (PP) as templates. Successful amplification was obtained both with male and female gonad samples and no sequence differences were found according to sex. This is a surprising finding, as figla was expected to be an exclusive ovarian marker and the presence of a specific transcript of this gene was only expected in female gonads. The alignment of the predicted amino acid sequences (Figure S4) revealed a high identity with Figla proteins of several teleosts. A Helix-loop-helix domain was identified (Figure S4), which is a diagnostic feature of the Figla transcription factor, enabling the conversion of monomers to trans-activating dimmers. The phylogenetic analysis (Figure 4) revealed a preferential grouping with zebrafish Figla, and a closer evolutionary relatedness to other teleosts' proteins, thus confirming our isolate as a partial sequence of the Squalius Figla ortholog.


Sex determination in the Squalius alburnoides complex: an initial characterization of sex cascade elements in the context of a hybrid polyploid genome.

Pala I, Schartl M, Thorsteinsdóttir S, Coelho MM - PLoS ONE (2009)

Unrooted Neighbour-Joining tree obtained among the FIGLA family of proteins.Dre-FIGLA- Danio rerio, Tni-FIGLA- Tetraodon nigroviridis, Kma-FIGLA- Kryptolebias marmoratus, Hsa- FIGLA- Homo sapiens, Rno-FIGLA- Rattus norvegicus, and Xtr FIGLA- Xenopus (Silurana) tropicalis. Bootstrap values are shown above the branches. ▴ S. pyrenaicus males (PP-M); ▵ females (PP-F) and • S. alburnoides (AA).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2713423&req=5

pone-0006401-g004: Unrooted Neighbour-Joining tree obtained among the FIGLA family of proteins.Dre-FIGLA- Danio rerio, Tni-FIGLA- Tetraodon nigroviridis, Kma-FIGLA- Kryptolebias marmoratus, Hsa- FIGLA- Homo sapiens, Rno-FIGLA- Rattus norvegicus, and Xtr FIGLA- Xenopus (Silurana) tropicalis. Bootstrap values are shown above the branches. ▴ S. pyrenaicus males (PP-M); ▵ females (PP-F) and • S. alburnoides (AA).
Mentions: Fragments of approximately 300 bp corresponding to a putative figla product were obtained using S. alburnoides (AA) and S.pyrenaicus (PP) as templates. Successful amplification was obtained both with male and female gonad samples and no sequence differences were found according to sex. This is a surprising finding, as figla was expected to be an exclusive ovarian marker and the presence of a specific transcript of this gene was only expected in female gonads. The alignment of the predicted amino acid sequences (Figure S4) revealed a high identity with Figla proteins of several teleosts. A Helix-loop-helix domain was identified (Figure S4), which is a diagnostic feature of the Figla transcription factor, enabling the conversion of monomers to trans-activating dimmers. The phylogenetic analysis (Figure 4) revealed a preferential grouping with zebrafish Figla, and a closer evolutionary relatedness to other teleosts' proteins, thus confirming our isolate as a partial sequence of the Squalius Figla ortholog.

Bottom Line: Dmrt1 and wt1 transcripts were found at early stages of male development in S. alburnoides and are most likely implicated in the process of gonad development.For the first time in the study of this hybrid complex, it was possible to directly compare the gene expression patterns between the bisexual parental species and the various hybrid forms, for an extended set of genes.The contribution of these genes to gonad integrity maintenance and functionality is apparently unaltered in the hybrids, suggesting that no abrupt shifts in gene expression occurred as a result of hybridisation.

View Article: PubMed Central - PubMed

Affiliation: Centro de Biologia Ambiental, Departamento de Biologia Animal, Faculdade de Ciências da Universidade de Lisboa, Lisbon, Portugal. iapala@fc.ul.pt

ABSTRACT

Background: Sex determination processes vary widely among different vertebrate taxa, but no group offers as much diversity for the study of the evolution of sex determination as teleost fish. However, the knowledge about sex determination gene cascades is scarce in this species-rich group and further difficulties arise when considering hybrid fish taxa, in which mechanisms exhibited by parental species are often disrupted. Even though hybridisation is frequent among teleosts, gene based approaches on sex determination have seldom been conducted in hybrid fish. The hybrid polyploid complex of Squalius alburnoides was used as a model to address this question.

Methodology/principal findings: We have initiated the isolation and characterization of regulatory elements (dmrt1, wt1, dax1 and figla) potentially involved in sex determination in S. alburnoides and in the parental species S. pyrenaicus and analysed their expression patterns by in situ hybridisation. In adults, an overall conservation in the cellular localization of the gene transcripts was observed between the hybrids and parental species. Some novel features emerged, such as dmrt1 expression in adult ovaries, and the non-dimorphic expression of figla, an ovarian marker in other species, in gonads of both sexes in S. alburnoides and S. pyrenaicus. The potential contribution of each gene to the sex determination process was assessed based on the timing and location of expression. Dmrt1 and wt1 transcripts were found at early stages of male development in S. alburnoides and are most likely implicated in the process of gonad development.

Conclusions/significance: For the first time in the study of this hybrid complex, it was possible to directly compare the gene expression patterns between the bisexual parental species and the various hybrid forms, for an extended set of genes. The contribution of these genes to gonad integrity maintenance and functionality is apparently unaltered in the hybrids, suggesting that no abrupt shifts in gene expression occurred as a result of hybridisation.

Show MeSH
Related in: MedlinePlus