The conservation of number and location of 18S sites indicates the relative stability of rDNA in species of Pentatomomorpha (Heteroptera)

Abstract

Fluorescent in situ hybridization (FISH) with rDNA probes has been used for comparative cytogenetics studies in different groups of organisms. Although heteropterans are a large suborder within Hemiptera, studies using rDNA are limited to the infraorder Cimicomorpha, in which rDNA sites are present in the autosomes or sex chromosomes. We isolated and sequenced a conserved 18S rDNA region of Antiteuchus tripterus (Pentatomidae) and used it as a probe against chromosomes of 25 species belonging to five different families of Pentatomomorpha. The clone pAt05, with a length of 736 bp, exhibited a conserved stretch of 590 bp. FISH analysis with the probe pAt05 always demonstrated hybridization signals in sub-terminal positions, except for Euschistus heros. Apparently, there is a tendency for 18S rDNA sites to locate in autosomes, except for Leptoglossus gonagra and Euryophthalmus rufipennis, which showed signals in the m- and sex chromosomes, respectively. Although FISH has produced evidence that rearrangements are involved in rDNA repositioning, whether in different autosomes or between sex and m-chromosomes, we have no conclusive evidence of what were the pathways of these rearrangements based on the evolutionary history of the species studied here. Nevertheless, the diversity in the number of species analyzed here showed a tendency of 18S rDNA to remain among the autosomes.

Chromosomal evolutionary dynamics of four multigene families in Coreidae and Pentatomidae (Heteroptera) true bugs

“…Among previously studied Coreidae as well as the species analyzed in this study, no change in the number of 18S rDNA sites per diploid genome was evident. Moreover, the location was conserved terminally in one autosomal pair, except in L. gonagra, with clusters in the m-chromosomes (Bardella et al 2013). These data suggest that the mechanisms that could cause dispersion of 18S rDNA sites are operating more efficiently in Pentatomidae than in Coreidae.…”

“…The published data for 18S rDNA mapping in Pentatomidae reveal that the modal pattern is two autosomal clusters per diploid genome, described in eight species. Variant cases have been documented; for example, one to three clusters per diploid genome with variable locations involving autosomes and one or both sex chromosomes (González-García et al 1996;Papeschi et al 2003;Grozeva et al 2011;Bardella et al 2013). These variable situations could be considered as derived characteristics.…”

“…This contrasts with the data for Pentatomidae, with a conserved gross karyotype but a discrete diversity in the location of the clusters of multigene families, indicating genome dynamics for these markers. The findings are discussed to shed light on the possible causes for the Communicated (Bardella et al 2013). The Pentatomomorpha infraorder includes families exhibiting distinct macro-chromosomal features, i.e., diploid numbers.…”

“…Among these, some multigene families are tandemly organized, and the chromosomal location of these sequences has been useful for the elucidation of chromosomal evolution in different groups, including insects (see for example Cabrero et al 2009;Nguyen et al 2010;Cabral-de-Mello et al 2011a, b;Bardella et al 2013;Anjos et al 2015). The multigene families most used as chromosomal markers in insects; i.e., rDNAs, histone genes and, to a lesser extent, U snDNA, have revealed variable patterns for the number and location of the clusters, depending on the group studied.…”

“…In the suborder Heteroptera, which comprises approximately 40,000 species with holocentric chromosomes (Ueshima 1979;Weirauch and Schuh 2011), the mapping of multigene families is restricted to 18S rDNA (Panzera et al 2012; Bardella et al 2013;Chirino et al 2013;Golub et al 2015). Among the infraorders studied, the data have revealed diversity in the number and location of clusters in Triatoma, and conservation in the genus Rhodnius (Reduviidae, Cimicomorpha) (Panzera et al 2012;Pita et al 2013).…”