Highly Similar Morphologies Between Chromosomes Bearing U2 snRNA Gene Clusters in the Group Astyanax Baird and Girard, 1854 (Characiformes, Characidae): An Evolutionary Approach in Species with 2n = 36, 46, 48, and 50

Abstract

Repetitive sequences and their chromosomal locations have been widely studied in species of the Astyanax genus. However, the chromosomal organization of U2 snDNA remains largely unknown. The aims of this study were to examine the chromosomal contexts of U2 snRNA and 5S rRNA genes in Astyanax species and determine the degree of chromosome morphological similarity between species with different diploid numbers. Clusters of U2 snDNA and 5S rDNA were determined in nine species of Astyanax, including two karyomorphs of Astyanax fasciatus Cuvier, 1819. All species exhibited U2 snDNA clusters on two chromosome pairs, except Astyanax mexicanus De Filippi, 1853 (one pair). The 5S rDNA clusters were located on one chromosome pair in Astyanax altiparanae Garutti and Britski, 2000, and Astyanax marionae Eigenmann, 1911, two pairs in Astyanax abramis Jenyns, 1842, Astyanax asuncionensis Géry, 1972, Astyanax bockmanni Vari and Castro, 2007, Astyanax eigenmanniorum Cope, 1894, A. fasciatus (karyomorphs I and II), and Astyanax schubarti Britski, 1964, and four pairs in A. mexicanus. The relationships between the repetitive sequences in different species suggest that A. schubarti and A. mexicanus exhibit an unusual U2 snDNA chromosomal format as a result of events occurring in the evolutionary history of the Astyanax group.

Chromosomal organization of retrotransposon Rex1 in Astyanax species (Characiformes, Characidae)

“…This study is a continuation of previous publications from our group (Piscor et al 2015(Piscor et al , 2016Parise-Maltempi 2016a, 2016b). Amplification of Rex1 sequences from Astyanax species resulted in fragments of approximately 600 bp for all the samples analyzed.…”

“…Given the important roles of retrotransposable elements on fish evolution, their mapping is very important for understanding the genome structure and evolution process in Astyanax (Characiformes, Characidae) genus (Silva et al 2013(Silva et al , 2014Daniel et al 2015;. Astyanax is an interesting group because present high karyotype diversity, including species with 2n = 52, 50, 48, 46 and 36 chromosomes (Tenório et al 2013;Piscor et al 2015;Nishiyama et al 2016;Piscor et al 2016;Parise-Maltempi 2016a, 2016b).…”

Cytogenetic markers using single-sequence probes reveal chromosomal locations of tandemly repetitive genes in scleractinian coral Acropora pruinosa

“…This suggests the possible presence of other repetitive histone loci that can be observed in scleractinian chromosomes. Surprisingly, a unique arrangement of repetitive arrays involving linkage between histone and 5S rRNA genes was observed among crustaceans 44 and fish 45 , 46 .…”

Dynamics of tandemly repeated DNA sequences during evolution of diploid and tetraploid botiid loaches (Teleostei: Cobitoidea: Botiidae)

“…Together with species in our study, this tandemly repeated multigene family has been mapped already in about 80 species placed in ten fish orders (reviewed in [ 105 ]; among more recent papers, see, e.g. : [ 89 , 123 – 125 ]), with our study adding the first records for Cypriniformes. About half of the surveyed teleost fish species exhibits a single pair of U2-bearing chromosomes and internal or proximal chromosomal localization [ 89 , 105 , 124 ].…”