Comparative analysis of the location of rDNA in the Palaearctic bushcricket genus Isophya (Orthoptera: Tettigoniidae: Phaneropterinae)

Abstract

Abstract. The present study focused on the evolution of the karyotype in 21 taxa of the genus Isophya, which was done by mapping the location on the chromosomes of ribosomal RNA (rRNA) coding genes using fluorescence in situ hybridization (FISH) with an 18S rDNA probe and using silver staining (AgNO3) to evaluate the activity of major rDNA clusters. Since the chromosome number and sex determination do not vary in this genus, the above markers were used in a detailed comparison of the cytogenetic features of species of Isophya. The species analyzed were placed into three groups based on the location of rDNA on their chromosomes: (1) rDNA-FISH signals only on the two long pairs of autosomes, (2) rDNA-FISH signals on one long and one short pair of autosomes, and (3) rDNA-FISH signals on three to five different sized pairs of autosomes. These groupings partly correspond to the morphological groupings proposed in earlier studies. One long pair of autosomes frequently carried rDNA in all the Isophya species and probably is a plesiomorphic character for these taxa. The cytogenetic mapping revealed great variability among Isophya species in the chromosomal location of major rDNA clusters. Our results suggest that the observed variation in the number of rDNA clusters can be an important species-group specific phylogenetic marker. Analysis of 18S rDNA hybridization signals showed that the evolutionary dynamics of rDNA in this genus is remarkably high and accompanied by changes in the structure of chromosomes bearing rDNA at an inter-and intra-specific level. The telomeric sequence (TTAGG)n hybridized with the termini of most of chromosomes, however, some chromosome ends lacked signals probably due to a low copy number of telomeric repeats.

Review of the Plangia graminea (Serville) complex and the description of new Plangia species from East Africa (Orthoptera: Phaneropteridae, Phaneropterinae) with data on habitat, bioacoustics, and chromosomes

“…The presence of rDNA loci only on a single bivalent, preferentially located in the paracentromeric region distally, was previously observed in other Phaneropterinae with different chromosome numbers in the European genera Odontura (Grzywacz et al 2014). The present study demonstrates clearly that the telomeric regions of the chromosomes in Plangia are composed of the (TTAGG) n telomeric repeats similar to the African Lunidia viridis (Hemp et al 2010a) and other tettigoniids (e.g., Warchałowska-Śliwa et al 2011Warchałowska-Śliwa et al , 2013Grzywacz et al 2011). In conclusion, our results on mechanisms changing the morphology of the X chromosome resulting in differences of the heterochromatin composition and distribution on the chromosomes are probably good markers to illuminate genomic evolution in Plangia species.…”

Interstitial NORs, Fragile Sites, and Chromosome Evolution: A Not So Simple Relationship - The Example of <b><i>Melolontha melolontha</i></b> and Genus <b><i>Protaetia </i></b>(Coleoptera: Scarabaeidae)

“…, and particularly in the short arms or centromeric regions of acrocentrics, as in man and great apes [Henderson et al, 1972 and many insects, such as grasshoppers [Cabrero and Camacho, 2008] and bushcrickets [Grzywacz et al, 2011]. In many species, telomeric NORs are multiple and variable in number [Volleth, 1987;Nirchio et al, 2007].…”

The genus Ectadia (Orthoptera: Phaneropteridae: Phaneropterinae) in East Asia: description of a new species, comparison of its complex song and duetting behavior with that of E. fulva and notes on the biology of E. fulva

“…Constitutive heterochromatin was revealed by the C-banding technique as described by Sumner (1972). Fluorescence in situ hybridization (FISH) with ribosomal 18S rDNA (rDNA) genes was performed exactly as described in Grzywacz et al (2011). Diagnosis.-Differs from all species of the genus in proportions of anal (1/3) and basal (2/3) part of the stridulatory file and number (about 100; Table 1) and distribution of teeth on the stridulatory file (Figs 2, 3).…”