The 5S rDNA in two Abracris grasshoppers (Ommatolampidinae: Acrididae): molecular and chromosomal organization

Abstract

placed in one bivalent, while type-I occurred in multiple copies in distinct chromosomes. In Abracris, the evolution of 5S rDNA was apparently influenced by the chromosomal distribution of clusters (single or multiple location), resulting in a mixed mechanism integrating concerted and birth-and-death evolution depending on the unit.

Uncovering the molecular organization of unusual highly scattered 5S rDNA: The case of Chariesterus armatus (Heteroptera)

“…Extreme genome variability for this sequence was reported in fishes reaching up to ten different variants (Campo et al, 2009;Merlo et al, 2013;Barman et al, 2016). Similar cases have been reported in invertebrates with up to five variants per genome (Vierna et al, 2009;Freire et al, 2010;Perina et al, 2011;Vizoso et al, 2011;Bueno et al, 2016).…”

“…In C. armatus, the highly scattered hybridization signals of 5S rDNA, forming multiples blocks over C. armatus chromosomes, suggest putative duplication episodes for this gene that have acquired genome mobility. This contrasts with T. fosteriana that showed discrete blocks (Mizuochi et al, 2007) as commonly seen in other Heteroptera (Bardella et al, 2016) and other animal groups (Insua et al, 2001;Martins and Galetti, 2001;Martins et al, 2002;da Silva et al, 2011;Rodrigues et al, 2012;Merlo et al, 2013;Bueno et al, 2016;Liu et al, 2017). The scattered chromosomal pattern of 5S rDNA seen in C. armatus is unusual, however, it has been reported for other multigene families, such as U2 snDNA in the fish Amphuchthys cryptocentrus and Porichtys plectrodon (Úbeda-Manzanaro et al, 2010).…”

“…In some species, different variants of 5S rDNAvariable in size and compositionoccupy different chromosomal loci (see Martins and Galetti, 2001;Martins et al, 2002;Rodrigues et al, 2012;Merlo et al, 2013;Bueno et al, 2016;Liu et al, 2017). 5S rDNA variants were noticed for example in grasshoppers (Bueno et al, 2016), crustaceans (Perina et al, 2011), mollusks (Vierna et al, 2009;Vizoso et al, 2011), amphibians (Rodrigues et al, 2012;Liu et al, 2017), freshwater stingrays (Pinhal et al, 2011) and fish (Martins and Galetti, 2001). Interestingly, in H. histrio, which has one cluster per haploid genome, more than two variants of 5S rDNAs were recognized based on the NTS regions; this is similar to the fish D. sargus, which has multiple 5S rDNA variants but exhibits restriction of the clusters to only two chromosomes (Merlo et al, 2013).…”

“…The 5S rDNA transcriptional unit consists of a 120-bp that is evolutionarily conserved, even between phylogenetically distant organisms, and a non-transcribed spacer (NTS) that is subject to sequence modification, exhibiting variations in size and/or nucleotide sequence (Denis and Wegnez, 1978;Long and David, 1980;Wasko et al, 2001;Rebordinos et al, 2013). Variability within NTS sequences is caused by nucleotide insertions-deletions or substitutions, as well as by the presence of microsatellites and transposable elements (TEs), contributing for NTS evolution within and between taxa (Pasolini et al, 2006;da Silva et al, 2011;Merlo et al, 2010;Merlo et al, 2013;Bueno et al, 2016).…”

“…Concerted evolution results in repeat homogenization, while birthand-death promotes sequence diversification (Nei and Rooney and Ward, 2005). Mixing patterns involving concerted evolution and birth-and-death have been proposed for 5S rDNA evolution in some groups such as freshwater stingrays (Pinhal et al, 2011), mollusks (Freire et al, 2010;Vizoso et al, 2011), echinoderms (Caradonna et al, 2007) and grasshoppers (Bueno et al, 2016). Furthermore, the 5S rDNA association with other sequences, as well as loci number and chromosomal location, could influence the evolution of 5S rDNA (Cross and Rebordinos, 2005;Manchado et al, 2006;Vierna et al, 2011;Bueno et al, 2016).…”