Limits...
Evidence for a genetic sex determination in Cnidaria, the Mediterranean red coral ( Corallium rubrum )

View Article: PubMed Central - PubMed

ABSTRACT

Sexual reproduction is widespread among eukaryotes, and the sex-determining processes vary greatly among species. While genetic sex determination (GSD) has been intensively described in bilaterian species, no example has yet been recorded among non-bilaterians. However, the quasi-ubiquitous repartition of GSD among multicellular species suggests that similar evolutionary forces can promote this system, and that these forces could occur also in non-bilaterians. Studying sex determination across the range of Metazoan diversity is indeed important to understand better the evolution of this mechanism and its lability. We tested the existence of sex-linked genes in the gonochoric red coral (Corallium rubrum, Cnidaria) using restriction site-associated DNA sequencing. We analysed 27 461 single nucleotide polymorphisms (SNPs) in 354 individuals from 12 populations including 53 that were morphologically sexed. We found a strong association between the allele frequencies of 472 SNPs and the sex of individuals, suggesting an XX/XY sex-determination system. This result was confirmed by the identification of 435 male-specific loci. An independent test confirmed that the amplification of these loci enabled us to identify males with absolute certainty. This is the first demonstration of a GSD system among non-bilaterian species and a new example of its convergence in multicellular eukaryotes.

No MeSH data available.


Related in: MedlinePlus

Plot of the number of male-specific loci possessed by an individual as a function of the individual coordinate on the fifth axis of the PCA. Morphologically sexed individuals are indicated (red: females, blue: males).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC5383831&req=5

RSOS160880F3: Plot of the number of male-specific loci possessed by an individual as a function of the individual coordinate on the fifth axis of the PCA. Morphologically sexed individuals are indicated (red: females, blue: males).

Mentions: Finally, as a validation test, we crossed the results obtained by PCA and by sex-specific loci by searching the presence of the 435 male-specific loci in all 354 individuals (figure 3). Twenty-four per cent of PCA-identified males possessed all 435 male-specific loci and 80% of the individuals possessed 90% of these loci. Some of these loci may have been lost during library preparation and sequencing, or due to allele dropout, thereby explaining their absence in some of the males. Furthermore, the male-specific loci have been found from 25 individuals, and it is likely that some of them have been detected erroneously if the pattern of technical missing data for a locus followed by chance the male/female distribution. All of the 435 male-specific loci were absent in 40% of PCA-identified females, and 97% of PCA-identified females contained less than 1% of male-specific loci. Figure 3 illustrates the correlation between the three methods of sex identification presented here (coordinate on the fifth axis of the PCA, number of male-specific loci and morphological identification). We observed an extremely good correlation between these three methods, the groups of males and females being well defined in each case. The three misclassified females identified from the PCA also possessed a high number of male-specific loci, and seemed to be genetically male. Such incongruence between sex genotype and phenotype may result from an environmental sexual reversal during sexual differentiation [34], or from the existence of females with the XY genotype, as already described in several mammals [35]. Finally, four individuals that have not been sexed morphologically presented female genotypes but between 15 and 65 male-specific loci. Further analysis is needed to determine the sexual identity of these individuals.Figure 3.


Evidence for a genetic sex determination in Cnidaria, the Mediterranean red coral ( Corallium rubrum )
Plot of the number of male-specific loci possessed by an individual as a function of the individual coordinate on the fifth axis of the PCA. Morphologically sexed individuals are indicated (red: females, blue: males).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383831&req=5

RSOS160880F3: Plot of the number of male-specific loci possessed by an individual as a function of the individual coordinate on the fifth axis of the PCA. Morphologically sexed individuals are indicated (red: females, blue: males).
Mentions: Finally, as a validation test, we crossed the results obtained by PCA and by sex-specific loci by searching the presence of the 435 male-specific loci in all 354 individuals (figure 3). Twenty-four per cent of PCA-identified males possessed all 435 male-specific loci and 80% of the individuals possessed 90% of these loci. Some of these loci may have been lost during library preparation and sequencing, or due to allele dropout, thereby explaining their absence in some of the males. Furthermore, the male-specific loci have been found from 25 individuals, and it is likely that some of them have been detected erroneously if the pattern of technical missing data for a locus followed by chance the male/female distribution. All of the 435 male-specific loci were absent in 40% of PCA-identified females, and 97% of PCA-identified females contained less than 1% of male-specific loci. Figure 3 illustrates the correlation between the three methods of sex identification presented here (coordinate on the fifth axis of the PCA, number of male-specific loci and morphological identification). We observed an extremely good correlation between these three methods, the groups of males and females being well defined in each case. The three misclassified females identified from the PCA also possessed a high number of male-specific loci, and seemed to be genetically male. Such incongruence between sex genotype and phenotype may result from an environmental sexual reversal during sexual differentiation [34], or from the existence of females with the XY genotype, as already described in several mammals [35]. Finally, four individuals that have not been sexed morphologically presented female genotypes but between 15 and 65 male-specific loci. Further analysis is needed to determine the sexual identity of these individuals.Figure 3.

View Article: PubMed Central - PubMed

ABSTRACT

Sexual reproduction is widespread among eukaryotes, and the sex-determining processes vary greatly among species. While genetic sex determination (GSD) has been intensively described in bilaterian species, no example has yet been recorded among non-bilaterians. However, the quasi-ubiquitous repartition of GSD among multicellular species suggests that similar evolutionary forces can promote this system, and that these forces could occur also in non-bilaterians. Studying sex determination across the range of Metazoan diversity is indeed important to understand better the evolution of this mechanism and its lability. We tested the existence of sex-linked genes in the gonochoric red coral (Corallium rubrum, Cnidaria) using restriction site-associated DNA sequencing. We analysed 27 461 single nucleotide polymorphisms (SNPs) in 354 individuals from 12 populations including 53 that were morphologically sexed. We found a strong association between the allele frequencies of 472 SNPs and the sex of individuals, suggesting an XX/XY sex-determination system. This result was confirmed by the identification of 435 male-specific loci. An independent test confirmed that the amplification of these loci enabled us to identify males with absolute certainty. This is the first demonstration of a GSD system among non-bilaterian species and a new example of its convergence in multicellular eukaryotes.

No MeSH data available.


Related in: MedlinePlus