Chromosomal mapping of telomeric and interstitial TTAGG repeats in six species of Belostoma (Heteroptera: Belostomatidae)

M. DALÍKOVA; CHIRINO M. G.; F. MAREC; M. J. BRESSA; M. DALÍKOVA; CHIRINO M. G.; M. J. BRESSA; F. MAREC

Foz do Iguaçu

Congreso; 21st International Chromosome Conference; 2016

International Chromosome and Genome Society, Brazilian Genetics Society

The (TTAGG)n sequence, the ancestral motif of insect telomeres, shows highly conserved chromosomal localization across the phylogenetic tree of insects except those orders, in which it was replaced with another motif or an alternative mechanism of telomere elongation. However, in a few species additional interstitial telomeric sequences (ITS) were found. The occurrence of ITS has been associated with the karyotype evolution through telomere-telomere fusions. In giant water bugs of the genus Belostoma, karyotypes of individual species differ from each other in chromosome number and sex chromosome system. The chromosome number changed during speciation by fragmentation of the single ancestral X chromosome, resulting in a multiple sex chromosome system. Furthermore, several autosome-autosome fusions and a fusion between sex chromosome pair and NOR-autosome pair resulted in reducing the number of chromosomes and increasing their size. In this study, we mapped the chromosomal distribution of TTAGG repeats in Belostoma candidulum (2n = 12 + XY/XX), B. dentatum (2n = 26 + X1X2Y/X1X1X2X2), B. elegans (2n = 26 + X1X2Y/X1X1X2X2), B. elongatum (2n = 26 + X1X2Y/X1X1X2X2), B. micantulum (2n = 14 + XY/XX), and B. oxyurum (2n = 6 + XY/XX) by FISH with the insect telomeric probe. Hybridization signals of the probe at the end of chromosomes confirmed the presence of TTAGG repeats in the telomeres of all species examined. In species with reduced chromosome numbers, we observed additional hybridization signals in interstitial positions, indicating the occurrence of ITS. Comparison of the ITS distribution between the closely related species supports the hypothesis that chromosome fusions played a major role in the karyotype evolution during speciation of the genus Belostoma.