Characterization of a Novel Tc1-Like Transposon From Bream (Cyprinidae, Megalobrama) and Its Genetic Variation in the Polyploidy Progeny of Bream–Red Crucian Carp Crosses

Abstract

Crossing the cyprinids diploid blunt snout bream Megalobrama amblycephala (BSB) and Carassius auratus red var. (RCC) generated sterile triploid (3nRB) and fertile tetraploid (4nRB) hybrid offspring. Utilizing inverted terminal repeats (ITRs) of transposon Tdr1 from Danio rerio as PCR primer, the results showed that evident change in the number of Tc1-like transposons in 4nRB relative to BSB occurred, whereas such change did not arise in 3nRB compared to BSB. No Tc1-like transposon was found in RCC. A novel transposon was isolated from both BSB and 3nRB and designated as Tma1, which consisted of multiple copies after dot-blot hybridization. Based on the analysis of PCR amplified flanking sequence, characterization of Tma1 indicated that this element flanked by a duplicated TA dinucleotide and harbored an ITR of about 224 bp. Tma1 also harbored an incomplete transposase gene. Another novel transposon designated as Tte1 was detected in 4nRB, which harbored an ITR of roughly 130 bp and consisted of multiple copies, but had no transposase gene. The analysis of PCR amplification and Southern blot hybridization showed that DNAs of 4nRB, which were hybridized to DIG-labeled pTma1, did not give band by PCR with Tma1 primer, on the other hand, 7 of 15 DNA samples from BSB, which were hybridized to DIG-labeled pTte1, did not produce band by PCR with Tte1 primer. These results suggest that Tte1 may be a recent invasion in BSB population and burst in 4nRB offspring. Our data provide clues as to the possible role of transposons as a driving mechanism for genomic evolution.

Distant hybridization leads to different ploidy fishes

“…A novel transposon termed Tte1 was detected in the 4nRB [46], suggesting that the 4nRB was also a good polyploid model species for investigating evolution.…”

Analysis of the spotted gar genome suggests absence of causative link between ancestral genome duplication and transposable element diversification in teleost fish

“…Rediploidization often observed after tetraploidization during evolution might also generate the massive formation of pseudogenes that can serve as new insertion territories for TEs. Beside sporadic studies in fish and other species (De Boer, Yazawa, Davidson, & Koop, 2007;Liu et al, 2009), almost nothing is known on the relationship between polyploidization and TE activity in animals. Particularly, the effect of 3R on TE evolution has not been studied so far in fish.…”

Genetic and Epigenetic Changes Involving (Retro)transposons in Animal Hybrids and Polyploids

“…Genomic studies of such hybrids have not yet been initiated, and therefore poeciliid, cyprinid, and cobitid fish would be particularly attractive targets for genome-wide surveys. In polyploid carp hybrids, a Tc1-like retrotransposon was shown to be mobilized [Liu et al, 2009]. In the cyprinid Squalius alburnoides , transcriptomic studies point at increased miRNA expression in triploids in comparison to mid-parent values, possibly reflecting restoration of dosage balance to the diploid level [Inácio et al, 2012].…”