The molecular composition of the telomeres in true bugs’ chromosomes remains a mystery

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An international team from the Zoological institute RAS (St Petersburg) and the Institute of Biodiversity and Ecosystem Research, BAS (Sofia) showed that true bugs differed from the majority of other insects in molecular composition of telomeres. The study was published in Comparative Cytogenetics.

In the 1930s B. McClintock from the University of Missouri, Columbia and H.J. Muller from the University of Edinburgh discovered (independently of one another) that chromosomes carry special components, or “telomeres”, which stabilize their structure and protect them from destruction. At present, it is known, that telomeres regulate cellular senescence (the cellular equivalent of aging) and their shortening plays the role of a molecular clock for the organism.

In most animal and plants, the telomeres consist of short DNA tandem motifs (repeated millions of times) and associated proteins. Comparative analysis of these motifs in various groups of organisms has showed that they are evolutionarily stable being invariant within a group.

The most common and (most probably) ancestral DNA motif of insect telomeres is known to be (TTAGG)n. Some Authors suggested the absence of this motif in true bugs (a large group of insects, among them bedbugs, firebugs, and significant agricultural pests) however this conclusion was based on available data, which are very scarce.

On the basis of the results obtained in several phylogenetically distant species studied by FISH (a technique for visualizing specific DNA sequences onto chromosomes) and dot-blot hybridization (a technique for detecting the presence/absence of target biomolecules in a sample) with a TTAGG probe, we confirmed that the insect consensus telomeric motif (TTAGG)n was lost in the evolution of true bugs.

To clarify the molecular composition of telomeres in these insects we used dot-blot hybridization of the genomic DNA from several true bug species with a number of telomeric probes known as specific to other organisms (ciliates, nematodes, shrimps, vertebrates, and plants). The result of these hybridization experiments was negative allowing suggesting that these telomerase-depended sequences are likewise not characteristic of the true bug telomeres.

Hence, the question of the molecular composition of true bug telomeres remains open and needs further studies.

Original source:
Grozeva S, Kuznetsova VG, Anokhin BA (2011) Karyotypes, male meiosis and comparative FISH mapping of 18S ribosomal DNA and telomeric (TTAGG)n repeat in eight species of true bugs (Hemiptera, Heteroptera). Comparative Cytogenetics 5(4): 355–374. doi: 10.3897/CompCytogen.v5i4.2307

Snejana Grozeva
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