Pereira, C.S.A., Pazian, M.F., Ráb, P. & Collares-Pereira, M.J. (2015) Dynamics of Rex3 in the genomes of endangered Iberian Leuciscinae (Teleostei, Cyprinidae) and their natural hybrids.Molecular Cytogenetics, 8(81), 1-10. DOI:10.1186/s13039-015-0180-1 (IF2015 1,506; Q4 Genetics & Heredity)
Iberian Leuciscinae are greatly diverse comprising taxa of hybrid origin. With highly conservative karyotypes, Iberian Chondrostoma s.l. have recently demonstrated sub-chromosomal differentiation and rapid genome restructuring in natural hybrids, which was confirmed by ribosomal DNA (rDNA) transposition and/or multiplication. To understand the role of repetitive DNAs in the differentiation of their genomes, a genetic and molecular cytogenetic survey was conducted in Achondrostoma oligolepis, Anaecypris hispanica, Iberochondrostoma lemmingii, I. lusitanicum,Pseudochondrostoma duriense, P. polylepis, Squalius pyrenaicus and hybrids between A. oligolepisx (P. duriense/P. polylepis), representing ‘alburnine’, chondrostomine and Squalius lineages.
Partial Rex3 sequences evidenced high sequence homology among Leuciscinae (≥98 %) and different fish families (80–95 %) proposing a relatively recent activity of these elements in the species inspected. Low nucleotide substitution rates (I. lusitanicum, P. duriense, P. polylepis and S. pyrenaicus demonstrating rapid and independent differentiation. Natural hybrids followed the same patterns of accumulation and association with repetitive sequences. An increased number of Rex3 clusters now associating also with translocated 45S rDNA clusters vouched for other genomic rearrangements in hybrids. Rex3 sequence phylogeny did not agree with its hosts’ phylogeny but the observed distribution pattern is congruent with an evolutionary tendency to protect its activity, a robust regulatory system and/or events of horizontal transfer.
This is the first report directed at retroelement physical mapping in Cyprinidae. It helped outlining conceivable ancestral homologies and recognizing retrotransposon activation in hybrids, being possibly associated with genome diversification within the subfamily. The extensive diversity of Iberian Leuciscinae makes them excellent candidates to explore the processes and mechanisms behind the great plasticity distinguishing vertebrate genomes.