Localization and activity of rDNA Genes in tiger beetles (Coleoptera: Cicindelinae)
ABSTRACT Siver staining of male meiotic nuclei of six species f the tiger beetle genus Cicindela (tribe Cicindelini), with multiple sex chromosomes, reveals the presence of active nucleolar organizing regions (NORs) in the sex vesicle. In one species, Cicindela melancholica, fluorescence in situ hybridization b(FISH) with a ribosomal probbe showed that rDNA genes are in one of the three X chromosomes and in the Y chromosome. Silver staining and FISH show that the related species Cicindela paludosa with a male XO system. has NORs located in one pair of autosomes. In Megacephala euphratica (tribe Megacephalini) these techniques indicate that NORs are located in three autosomal pairs but not in the single X chromosomes of males. In all these species the nucleolus can be seen from the onset of meiosis to the end of the diffuse stage; it disappears from diplotene to the end of meiosis and appears again during the spermatid stage. From these results it is concluded that: (i) the nucleolus does not seem to play a major role in the pairing and association of the multiple sex chromosomes during first meiotic prophase and metaphase; (ii) the occurrence of NORs in the heterosomes of species having multiple sex chromosomes is thought to be an ancestral condition for the genus Cicindela; and (iii) changes of location of NORs from heterosomes to the autosomes have occurred within species of this genus, at least in species showing extensive karyotypic repatterning.
Full-textDOI: · Available from: Eduard Petitpierre, Aug 20, 2015
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- "Mapping of the 45S region in certain species of the suborder Adephaga (Carabidae and Cicindelidae) showed a prevalence of ribosomal cistrons in an autosomal pair. However, some species exhibit variations , including a relatively large number of pairs carrying ribosomal cistrons or even cistrons in sex chromosomes [Galián et al., 1995; Proença et al., 2004; Schneider et al., 2007]. A greater number of families have been studied for the suborder Polyphaga (Scarabaeidae, Chrysomelidae , Tenebrionidae, Coccinelidae and Geotrupidae), which had shown that ribosomal genes are present in autosomal chromosomes, in sex chromosomes or in both [Vitturi et al., 1999; Schneider et al., 2007; Almeida et al., 2010; Cabral-de-Mello et al., 2011a]. "
ABSTRACT: The organization and mapping of multigene families can produce useful genetic markers, and its use may elucidate the mechanisms of karyotype variation and genomic organization in different groups of eukaryotes. To date, few species of Coleoptera have been analyzed using FISH for the location of multigene families. The purpose of this study was to use high-resolution chromosome mapping to establish the genomic organization of the 18S rDNA, 5S rDNA and histone H3 gene families in Lagria villosa. FISH was performed using 18S rDNA, 5S rDNA and histone H3 probes prepared via PCR labeling. Fiber-FISH for 18S and 5S rDNA indicated that both ribosomal elements are colocalized in the short arm of chromosome 4. Additionally, FISH, using the histone H3 probe, revealed that this sequence is found in only one autosomal pair and did not colocalize with rDNA. Fiber-FISH with 5S and 18S probes, used to improve the mapping resolution of these regions, showed that both genes are closely interspersed with varying amounts of both DNA classes. © 2015 S. Karger AG, Basel.Cytogenetic and Genome Research 05/2015; DOI:10.1159/000382047 · 1.91 Impact Factor
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- "Silver nitrate impregnation and fluorescent in situ hybridization (FISH) with ribosomal DNA probes are very useful, in general, to determine the pattern of NOR distribution among related species. In the case of Coleoptera , as a means to elucidate the nature of the association between the Xy p sex chromosomes [Galián et al., 1995; Petitpierre, 1996; Wolf, 1997], few (approximately 1%) were analyzed in recent decades with higher resolution techniques. These analyses could show differences between the systems and their modes of association even when all are Xy p . "
ABSTRACT: The Xy(p) sex determination mechanism is the system most frequent and ancestral to Coleoptera. Moreover, the presence of argyrophilous material associated with the sex bivalent is described as being responsible for the maintenance and association of these chromosomes. There are no karyotype data available regarding the genus Lagria and no consensus in the literature regarding the argyrophilous material present in the lumen of sex bivalent. Therefore, the aim of this work was to investigate the mechanism of sex chromosome bivalent association in Lagria villosa by analyzing the argyrophilous nature of the material present in the Xy(p) lumen. It was also intended to characterize L. villosa cytogenetically. The analysis of meiotic cells showed 2n = 18 = 16+Xy(p) for males and 2n = 18 = 16+XX in females and the meiotic formula was 2n = 8(II)+Xy(p). The C-banding showed blocks of pericentromeric heterochromatin in all chromosomes except in the y(p) chromosome. In these regions, the use of fluorochromes revealed the presence of heterochromatin containing GC rich DNA sequences. The study of synaptonemal complex showed a gradual increase in the electron-density of the axial elements of the sex chromosomes and their association with strongly electron-dense material. The pepsin pretreatment revealed that the material impregnated by silver is protein.Cytogenetic and Genome Research 08/2013; DOI:10.1159/000341674 · 1.91 Impact Factor
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- "In the tribes Carabini and Harpalini rDNA usually occurs in only one autosomal pair [De la Rúa et al., 1996; Martínez-Navarro et al., 2004]. However, the same is not observed in the tribes Cicindelini, Scaritini and Zabrini, which show high variation [Galián et al., 1995, 1999; Sánchez-Gea et al., 2000]. Sánchez-Gea et al.  studied 19 taxa in Zabrini and detected quantitative and qualitative variation among related species, subspecies, populations, and even individuals. "
ABSTRACT: The location of rDNA on chromosomes has been found to be highly variable in different groups of insect families of various orders. Yet, in other insect families the rDNA position is relatively constant. This contrast so far has received limited attention. We investigated the rDNA position on mitotic chromosomes in 18 species of Drosophila, 16 of which are from the tripunctata radiation, subgenus Drosophila, through fluorescent in situ hybridization (FISH). All species showed fluorescent signals only on the sex chromosomes. On the X chromosome a single fluorescent mark, but with variable locations, was found. On the Y, we observed variation both in location and in number of fluorescent marks (from 1 to 5). This constancy of chromosome location, in contrast to the great variability found in other groups, is consistent with the work carried out in other species of Drosophila. This suggests that the presence of a nucleolus organizer region (NOR) on each sex chromosome is probably an ancestral condition in the genus. Moreover, this difference in the variation of rDNA position among groups points out an interesting evolution question, which deserves further study.Cytogenetic and Genome Research 08/2009; 125(2):149-57. DOI:10.1159/000227840 · 1.91 Impact Factor