Abstract
BackgroundGrasshoppers from the Romaleidae family are well distributed in the Neotropical Region and represent a diversified and multicolored group in which the karyotype is conserved. Few studies have been conducted to understand the evolutionary dynamics of multigene families. Here, we report the chromosomal locations of the 18S and 5S rDNA and H3 histone multigene families in four grasshopper species from the Romaleidae family, revealed by fluorescent in situ hybridization (FISH).ResultsThe 5S rDNA gene was located in one or two chromosome pairs, depending on the species, and was found in a basal distribution pattern. Its chromosomal location was highly conserved among these species. The 18S rDNA was located in a single medium-sized chromosomal pair in all species analyzed. Its chromosomal location was near the centromere in the proximal or pericentromeric regions. The location of the H3 histone gene was highly conserved, with slight chromosomal location differences among some species. To our knowledge, this is the first report of a megameric chromosome carrying both the chromosomal markers 18S rDNA and the H3 histone genes, thereby expanding our understanding of such chromosomes.ConclusionsThe 5S and 18S rDNA genes and the H3 histone genes showed a conservative pattern in the species that we analyzed. A basal distribution pattern for 5S rDNA was observed with a location on the fourth chromosomal pair, and it was identified as the possible ancestral bearer. The 18S rDNA and H3 histone genes were restricted to a single pair of chromosomes, representing an ancestral pattern. Our results reinforce the known taxonomic relationships between Chromacris and Xestotrachelus, which are two close genera.
Highlights
Grasshoppers from the Romaleidae family are well distributed in the Neotropical Region and represent a diversified and multicolored group in which the karyotype is conserved
On the other hand, when data from the 10 ribosomal sites found in B. gigas, C. nuptialis, C. speciosa, and X. robustus are correlated with information from previous studies [22,25] related to the constitutive heterochromatin (CH) pattern, the results indicate four ribosomal sites in CH regions and six ribosomal sites outside CH regions
In summary, the 5S and 18S rDNA genes were preferentially located in medium-sized chromosomes among the Romaleidae grasshoppers, showing a conservative distribution pattern for these sequences
Summary
Grasshoppers from the Romaleidae family are well distributed in the Neotropical Region and represent a diversified and multicolored group in which the karyotype is conserved. Repetitive DNA elements constitute a large portion of eukaryotic genomes. These elements include tandemly arrayed satellites, minisatellites and microsatellites, multigene families, and dispersed repeats, such as transposons and retrotransposons [1]. The major ribosomal DNA family is formed by the association of one copy of 28S, 5,8S, and 18S rRNA, and these genes are separated by internal transcribed spacers (ITS1 and ITS2). Another ribosomal RNA gene is 5S rRNA, with a length of 160 bp. The repeats of this gene are separated by non-transcribed spacers (NTS). The 45S rRNA subunits are synthesized, processed, and partially assembled to form the ribosome subunits in the nucleolus, the 5S rRNA is synthesized elsewhere in the genome [1,4]
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