MicroRNA profiles reveal female allotetraploid hybrid fertility.

BACKGROUND: The bisexual fertile tetraploid fish is important in biological evolution. Tetraploid fish fertility is the key factor for stable inheritance. Therefore, elucidating tetraploid fish fertility at the molecular level is essential. MicroRNAs regulate gene expression and are involved in many aspects of gonad development. METHODS: Total RNA was isolated using TRIzol, followed by constructing small RNA libraries. And then, the qualified libraries were sequenced with the HiSeq 2500 SE50 system. The obtained clean reads were analyzed to identify conserved and novel miRNAs, and evaluate the expression, and also predict the target genes. The differential expressions of miRNAs were confirmed by RT-PCR. RESULTS: In this study, allotetraploid hybrid fish (4nAT) and diploid red crucian carp (RCC) ovaries were used to compare miRNA profiles. The results indicated that most of the highly expressed miRNAs were closely correlated with ovary maturation, and displayed no significant differences in expression. Moreover, 34 up-regulated and nine down-regulated miRNAs were found in 4nAT. The differentially expressed miRNAs were primarily involved in metabolism, defense mechanisms, and cytoskeleton production. CONCLUSIONS: This is the first study to provide new epigenetic evidences for tetraploid fish fertility and phenotypic changes as a result of increased ploidy.