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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 teleost Wt1 proteins and other WT1 orthologs.Dre-a-WT1- Danio rerio, Omy-a-WT1; Omy-b-WT1- Oncorhynchus mykiss, Aja-WT1- Anguilla japonica; Ola-WT1- Oryzias latipes; Hsa-WT1- Homo sapiens, Gga-WT1- Gallus gallus, Mmu-WT1- Mus musculus, and Rno-WT1- Rattus norvegicus. Bootstrap values are shown above the branches. Bootstrap values are shown above the branches. ▴ S. pyrenaicus (PP).
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pone-0006401-g002: Unrooted Neighbour-Joining tree obtained among the teleost Wt1 proteins and other WT1 orthologs.Dre-a-WT1- Danio rerio, Omy-a-WT1; Omy-b-WT1- Oncorhynchus mykiss, Aja-WT1- Anguilla japonica; Ola-WT1- Oryzias latipes; Hsa-WT1- Homo sapiens, Gga-WT1- Gallus gallus, Mmu-WT1- Mus musculus, and Rno-WT1- Rattus norvegicus. Bootstrap values are shown above the branches. Bootstrap values are shown above the branches. ▴ S. pyrenaicus (PP).

Mentions: Of all primer combinations tested, only the ones involving WT1-F1a and, WT1-R1a and WT1-R1b, respectively (Table 1) resulted in the production of sequence segments that could be identified as wt1. BLAST comparison revealed an overall similarity of all amplified fragments with WT1a transcripts of other teleosts. A larger PCR fragment was amplified with primers WT1 F5 and WT1-R1a (Table 2), using S. pyrenaicus gonad cDNA as template. The closer homology of our isolate to a-form Wt1 proteins of other telelosts was confirmed both in the phylogenetic tree comparing other Wt1 orthologs (Figure 2) and the alignments of the predicted amino acid sequence (Figure S2). Three distinct domains were identified in the S. pyrenaicus Wt1 isolate (Figure S2): a Wilm's tumour specific domain, and two (of the four) zinc finger DNA-binding motifs that characterize the C terminus of this transcription factor.


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 teleost Wt1 proteins and other WT1 orthologs.Dre-a-WT1- Danio rerio, Omy-a-WT1; Omy-b-WT1- Oncorhynchus mykiss, Aja-WT1- Anguilla japonica; Ola-WT1- Oryzias latipes; Hsa-WT1- Homo sapiens, Gga-WT1- Gallus gallus, Mmu-WT1- Mus musculus, and Rno-WT1- Rattus norvegicus. Bootstrap values are shown above the branches. Bootstrap values are shown above the branches. ▴ S. pyrenaicus (PP).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0006401-g002: Unrooted Neighbour-Joining tree obtained among the teleost Wt1 proteins and other WT1 orthologs.Dre-a-WT1- Danio rerio, Omy-a-WT1; Omy-b-WT1- Oncorhynchus mykiss, Aja-WT1- Anguilla japonica; Ola-WT1- Oryzias latipes; Hsa-WT1- Homo sapiens, Gga-WT1- Gallus gallus, Mmu-WT1- Mus musculus, and Rno-WT1- Rattus norvegicus. Bootstrap values are shown above the branches. Bootstrap values are shown above the branches. ▴ S. pyrenaicus (PP).
Mentions: Of all primer combinations tested, only the ones involving WT1-F1a and, WT1-R1a and WT1-R1b, respectively (Table 1) resulted in the production of sequence segments that could be identified as wt1. BLAST comparison revealed an overall similarity of all amplified fragments with WT1a transcripts of other teleosts. A larger PCR fragment was amplified with primers WT1 F5 and WT1-R1a (Table 2), using S. pyrenaicus gonad cDNA as template. The closer homology of our isolate to a-form Wt1 proteins of other telelosts was confirmed both in the phylogenetic tree comparing other Wt1 orthologs (Figure 2) and the alignments of the predicted amino acid sequence (Figure S2). Three distinct domains were identified in the S. pyrenaicus Wt1 isolate (Figure S2): a Wilm's tumour specific domain, and two (of the four) zinc finger DNA-binding motifs that characterize the C terminus of this transcription factor.

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