Allelic silencing is an important mechanism for coping with gene dosage changes in polyploid organisms that is well known in allopolyploid plants. Only recently, it was shown in the allotriploid fish Squalius alburnoides that this process also occurs in vertebrates. However, it is still unknown whether this silencing mechanism is common to other allopolyploid fish, and which mechanisms might be responsible for allelic silencing. We addressed these questions in a comparative study between Squalius alburnoides and another allopolyploid complex, the Amazon molly (Poecilia formosa). We examined the allelic expression patterns for three target genes in four somatic tissues of natural allo-anorthoploids and laboratory-produced tri-genomic hybrids of S. alburnoides and P. formosa. Also, for both complexes, we evaluated the correlation between total DNA methylation level and the ploidy status and genomic composition of the individuals. We found that allelic silencing also occurs in other allopolyploid organisms besides the single one that was previously known. We found and discuss disparities within and between the two considered complexes concerning the pattern of allele-specific expression and DNA methylation levels. Disparities might be due to intrinsic characteristics of each genome involved in the hybridization process. Our findings also support the idea that long-term evolutionary processes have an effect on the allele expression patterns and possibly also on DNA methylation levels.
The authors declare no competing or financial interests.
I.M.N.M. performed the S. alburnoides fish capture, carried out the crosses to obtain TGH, performed the experiments, analyzed the data, participated in the design of the study and drafted the manuscript. M.M.C. participated in the design of the study and helped draft the manuscript. M.S. participated in the design of the study, supervised its different components, produced the P. formosa TGHs and revised the manuscript. All authors gave final approval for publication.
This work was supported by Project PTDC/BIA-BIC/110277/2009 to M.M.C. and by a PhD grant (SFRH/BD/61217/2009) to I.M.N.M., both from the Portuguese National Science Foundation, Fundação para a Ciência e a Tecnologia.
The nucleotide sequences supporting this study are available from GenBank (accession numbers: KX681470 to KX681478; KX870949 to KX870952; KX870953 to KX870956; KX870957 to KX870960; KX870961 to KX870968; KX871034 to KX871041; KX871114 to KX871121; KX870969 to KX870978; KX870979 to KX870988; KX870989 to KX870999; KX871000 to KX871009; KX871010 to KX871015; KX871016 to KX871021; KX871022 to KX871027; KX871028 to KX871033; KX871042 to KX871053; KX871054 to KX871064; KX871065 to KX871077; KX871078 to KX871089; KX871090 to KX871095; KX871096 to KX871101; KX871102 to KX871107, KX871108 to KX871113; KX871122 to KX871132; KX871133 to KX871142; KX871143 to KX871150; KX871151 to KX871160; KX871161 to KX871166; KX871167 to KX871172; KX871173 to KX871178; KX871179 to KX871184).
Supplementary information available online at http://jeb.biologists.org/lookup/doi/10.1242/jeb.140418.supplemental
- Received March 13, 2016.
- Accepted July 19, 2016.
- © 2016. Published by The Company of Biologists Ltd