Abstract
BackgroundNucleolar dominance is an epigenetic phenomenon that occurs in interspecific hybrids and involves the expression of 45S rRNA genes inherited from one progenitor due to the silencing of the other progenitor’s rRNA genes. In this paper, changes in the genetics and expression of 45S rRNA genes in F1 and F2 hybrid progeny of blunt snout bream (BSB, Megalobrama amblycephala) × topmouth culter (TC, Culter alburnus) are investigated.ResultsThe 45S rDNA loci were analyzed by cloning, RT-PCR and sequencing methods. The results show that nucleolar dominance patterns differ in the F1 and F2 hybrids. In the F1 hybrids of BSB × TC, all the tested individuals inherited and expressed the 45S rRNA genes of both BSB and TC, indicating that nucleolar dominance is not established in the F1 hybrids. However, in the F2 hybrids of BSB × TC, five patterns are observed. Pattern 1 inherits and expresses only the 45S rRNA gene of BSB. Pattern 2 inherits the 45S rRNA gene from both BSB and TC, but only expresses the 45S rRNA of BSB. Pattern 3 inherits and expresses the 45S rRNA gene from both BSB and TC. Pattern 4 inherits the 45S rRNA gene from both BSB and TC, but only expresses the 45S rRNA gene of TC. Pattern 5 inherits and expresses only the 45S rRNA gene of TC.ConclusionsNucleolar dominance shows distinctive patterns in intergeneric hybrids of BSB × TC. It is not established in F1 hybrids and is random in F2 hybrids. This study provides new insights into the phenomenon of nucleolar dominance in genetic hybrids in vertebrates.Electronic supplementary materialThe online version of this article (doi:10.1186/s12863-016-0457-3) contains supplementary material, which is available to authorized users.
Highlights
Nucleolar dominance is an epigenetic phenomenon that occurs in interspecific hybrids and involves the expression of 45S rRNA genes inherited from one progenitor due to the silencing of the other progenitor’s rRNA genes
In eukaryotes, 45S rRNA genes are tandemly arrayed by the hundreds, and sometimes by the thousands, at chromosomal loci spanning millions of base pairs. rRNA genes are transcribed by RNA polymerase I (Pol I) into a precursor RNA that encodes the three largest RNA components of ribosomes [1, 2]
The results show that the genetics and expression patterns of 45S rRNA genes in the liver of mature individuals differ in F1 and F2 hybrids
Summary
Nucleolar dominance is an epigenetic phenomenon that occurs in interspecific hybrids and involves the expression of 45S rRNA genes inherited from one progenitor due to the silencing of the other progenitor’s rRNA genes. Nucleolar dominance is an epigenetic phenomenon that occurs in genetic hybrids and involves expression of the 45S rRNA genes inherited from only one progenitor. The genetics and expression of 45S rRNA genes have been studied by detecting single nucleotide polymorphism (SNP) sites in the 18S rRNA gene [12]. Total aNote: Pattern 1 inherits and expresses the single 45S rRNA gene of BSB. Pattern 4 inherits both the 45S rRNA gene from BSB and TC, but only expresses the 45S rRNA gene of TC. Pattern 5 inherits and expresses the single 45S rRNA gene of TC discovery. SNPs are detected because two peaks are observed in sequence traces in the heterozygous state, compared with a single peak in the homozygous state
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