Localization and activity of rDNA Genes in tiger beetles (Coleoptera: Cicindelinae)
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.
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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.
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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.
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- "Fluorescent in situ hybridization (FISH) has proven to be an efficient and routine method for the physical location of ribosomal genes in the chromosomes of several species. However, few species of Coleoptera have been studied using this procedure (Juan et al., 1993; Galián et al., 1995; Petitpierre, 1996; Galián and Hudson, 1999; Proenç a et al., 2002a,b; Bione et al., 2005a,b). Some studies using the FISH method on chromosomes of Coleoptera species have found different results from those obtained with silver nitrate impregnation. "
ABSTRACT: Alticinae has the greatest amount of biodiversity among the Chrysomelidae, with 40,000 described species, only 290 of which have been analyzed cytogenetically. The majority of studies refer to conventional staining and few species have been analyzed or have responded to differential staining methods. The aim of the present study was to describe an 18S rDNA probe for Alticinae and the location of this cluster in species of the Omophoita genus. The fragment of approximately 750bp obtained through a PCR (Polymerase Chain Reaction) amplification reaction with specific oligonucleotides to 18S rDNA was cloned and denominated pTZ_Ooct_18Sp and then submitted to automatic sequencing. The alignment of the sequences obtained through the sequencing of the clones generated a consensus sequence of 722bp for Omophoita octoguttata with 98% homology with other species of Alticinae. The analysis of mitotic cells of O. octoguttata and Omophoita magniguttis submitted to fluorescent in situ hybridization (FISH) with the 18S rDNA probe revealed that the ribosomal genes are located in 6th pair. O. magniguttis also has a second labeled pair. Omophoita personata exhibited nucleolar organizer regions associated to one autosome pair. The analysis of meiotic cells submitted to FISH revealed one labeled bivalent in metaphase I in O. octoguttata and O. personata and in one chromosome in metaphase II in O. octoguttata. FISH data suggest a conserved pattern in the species analyzed and an apomorphy of O. magniguttis karyotype. The rDNA 18S probe could be considered an important marker to evidence the karyotypic differentiation, not observed with conventional methodologies, in species considered karyotypically conserved and uniform.