The cloning of Dmc1 cDNAs and a comparative study of its expression in different ploidy cyprinid fishes

Abstract

Dmc1 (disrupted meiotic cDNA) is a functionally specific gene, which was firstly discovered in yeast and then found to encode a protein required for homologous chromosome synapsis during the process of meiosis. In this investigation, we cloned the partial cDNAs of Dmc1 of diploid red crucian carp, Japanese crucian carp, common carp, triploid crucian carp and allotetraploid hybrids by using a pair of degenerate primers based on the conservative sequence of amino acids of the DMC1 protein in yeast, mouse and human. The full length cDNAs were then obtained by rapid amplification of cDNA ends (RACE). Our data showed that the full length cDNAs of Dmc1 in the three diploid fishes are all 1375 bp long, while it is 1383 bp long in triploids and 1379 bp long in allotetraploids. And despite of the variation in length, all the cDNAs encode a protein of 342 amino acids. A high homology of 97.3% of the DMC1 protein can be drawn by comparing the amino acid sequences in the three diploids, which is also of 86%, 86% and 95% similarity to human, mouse and zebrafish, respectively. A comparative study of the expression pattern of Dmc1 was carried out by RT-PCR using specific primers against the same sequences of coding regions in different ploidy cyprinid fishes, from which it was showed that Dmc1 was expressed only in gonads of these five kinds of fishes. The expression pattern of Dmc1 in both ovaries and testes from different ploidy fishes within breeding season was also studied by Real-time PCR, and the results showed that the expression of this gene was greatly different among the three different ploidy fishes, which was the highest of triploid and lowest of allotetraploids. The histological sections data showed matured gonads of both diploid red crucian carp and allotetraploids in breeding season, although the latter demonstrated a higher maturation, and no gonadal maturation could be observed in triploids. In conclusion, we suggest that Dmc1 is specifically expressed in the period of meiosis in all the ploidy cyprinid fishes and directly related with the development of gonad in a manner of ploidy-independent way. And further, the high expression of Dmc1 in female triploids might be associated with abnormal meiosis and sterility.

Homoeologue expression insights into the basis of growth heterosis at the intersection of ploidy and hybridity in Cyprinidae

“…The expression level of the reference gene β-actin in the hybrids was estimated using the ratio of the transcript abundance to the gene copy using PCR and qRT-PCR of co-extracted DNA and RNA from the ovaries of diploid and allotetraploid individuals. β-actin expression is the same between fish of different ploidy and genome constitution, and in somatic organs and gonads16434445. In addition, we performed the multiple linear regression analysis on mstn and igf2 gene between the method of RNA-seq and qRT-PCR (Supplementary Fig.…”

Distant hybridization leads to different ploidy fishes

“…For example, 4nAT had two pairs of short barbels while the CC had two pairs of longer barbels and RCC had no barbel. The lateral scale number (30)(31)(32)(33)(34) of 4nAT was intermediate between that of CC (34)(35)(36)(37)(38)(39) and that of RCC (28)(29)(30).…”

“…The expression of this gene during the breeding season markedly differed among the three different ploidy fishes. The high expression of Dmc1 in female 3nJCs might be associated with their abnormal meiosis and sterility [30].…”

Determination of dosage compensation and comparison of gene expression in a triploid hybrid fish

“…The expression pattern of homologous genes is the focus of our attention. Recent reports show that duplicate gene pairs in hybrids may display homoeolog expression bias (HEB), where the two homoeologs are expressed unequally and often vary among tissues [19, 20]. The epigenetic remodeling including nuclear enlargement and increased complexity of the processes during cell division always results in both the activation and suppression of gene expression in polyploids [2].…”