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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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Related in: MedlinePlus

Expression patterns of figla in the adult gonads S. pyrenaicus and S. alburnoides.(a) S. alburnoides (AA genotype) testis; (b) S. alburnoides (PAA genotype) ovary and S. pyrenaicus (PP genotype) ovary with (c) antisense and (d) sense probes (positive signals in primary oocytes exemplified with black arrows; lower expression in early stage oocytes exemplified with grey arrows; cells in different maturation stages, not expressing the transcript are indicated by grey arrowheads). Germ cells (GS), early perinuclear (P), cortical alveolar (CA) and vitellogenic (V) oocytes. Scale bar = 100 µm (a, c, d); scale bar = 200 µm (b).
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pone-0006401-g006: Expression patterns of figla in the adult gonads S. pyrenaicus and S. alburnoides.(a) S. alburnoides (AA genotype) testis; (b) S. alburnoides (PAA genotype) ovary and S. pyrenaicus (PP genotype) ovary with (c) antisense and (d) sense probes (positive signals in primary oocytes exemplified with black arrows; lower expression in early stage oocytes exemplified with grey arrows; cells in different maturation stages, not expressing the transcript are indicated by grey arrowheads). Germ cells (GS), early perinuclear (P), cortical alveolar (CA) and vitellogenic (V) oocytes. Scale bar = 100 µm (a, c, d); scale bar = 200 µm (b).

Mentions: No sexual dimorphic expression of figla was observed in S. alburnoides. Amplification of a figla specific fragment was conducted successfully both in male and female gonad cDNA templates (Figure S8). Expression was observed in testes in locations compatible with expression in Sertoli cells (Figure 6a). In ovaries figla was highly expressed in late primary oocytes, both in bisexual parental species S. pyrenaicus and in the S. alburnoides hybrids, while only a faint signal was detected in primary oocytes (Figure 6b and c).


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)

Expression patterns of figla in the adult gonads S. pyrenaicus and S. alburnoides.(a) S. alburnoides (AA genotype) testis; (b) S. alburnoides (PAA genotype) ovary and S. pyrenaicus (PP genotype) ovary with (c) antisense and (d) sense probes (positive signals in primary oocytes exemplified with black arrows; lower expression in early stage oocytes exemplified with grey arrows; cells in different maturation stages, not expressing the transcript are indicated by grey arrowheads). Germ cells (GS), early perinuclear (P), cortical alveolar (CA) and vitellogenic (V) oocytes. Scale bar = 100 µm (a, c, d); scale bar = 200 µm (b).
© Copyright Policy
Related In: Results  -  Collection

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

pone-0006401-g006: Expression patterns of figla in the adult gonads S. pyrenaicus and S. alburnoides.(a) S. alburnoides (AA genotype) testis; (b) S. alburnoides (PAA genotype) ovary and S. pyrenaicus (PP genotype) ovary with (c) antisense and (d) sense probes (positive signals in primary oocytes exemplified with black arrows; lower expression in early stage oocytes exemplified with grey arrows; cells in different maturation stages, not expressing the transcript are indicated by grey arrowheads). Germ cells (GS), early perinuclear (P), cortical alveolar (CA) and vitellogenic (V) oocytes. Scale bar = 100 µm (a, c, d); scale bar = 200 µm (b).
Mentions: No sexual dimorphic expression of figla was observed in S. alburnoides. Amplification of a figla specific fragment was conducted successfully both in male and female gonad cDNA templates (Figure S8). Expression was observed in testes in locations compatible with expression in Sertoli cells (Figure 6a). In ovaries figla was highly expressed in late primary oocytes, both in bisexual parental species S. pyrenaicus and in the S. alburnoides hybrids, while only a faint signal was detected in primary oocytes (Figure 6b and c).

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