Distribution of TTAGG-specific telomerase activity in insects

Abstract

In most eukaryotes, telomeres consist of tandem arrays of a short repetitive DNA sequence. Insect telomeres are generally constituted by a (TTAGG)n repeat motif. Usually, telomeres are maintained by telomerase, a specialized reverse transcriptase that adds this sequence to chromosome ends. We examined telomerase activity in 15 species across Insecta. Telomerase activity was revealed in Isoptera, Blattaria, Lepidoptera, Hymenoptera, Trichoptera, Coleoptera, and Sternorrhyncha. In contrast, we were not able to detect telomerase activity in Orthoptera, Zygentoma, and Phasmida. Because we found telomerase activity in phylogenetically distant species, we conclude that a distribution pattern of (TTAGG)n sequence in Insecta is generally consistent with that of telomerase activity. Thus, the TTAGG-telomerase system is functional across the Insecta. Using real-time quantitative telomeric repeat amplification protocol (RTQ-TRAP) system, we quantified telomerase activity in different developmental stages and different tissues of a cockroach, Periplaneta americana. We show that telomerase is upregulated in young instars and gradually declines during development. In adults, it is most active in testes and ovaries. Thus, the telomerase activity of hemimetabolous insects seems to be associated with cell proliferation and organismal development.

Telomere structure in insects: A review

“…domestica ) revealed the TTAGG telomeric repeat in both those insects (Frydrychová et al, ). Nevertheless, real‐time quantitative telomeric repeat amplification protocol (RTQ‐TRAP) did not detect telomerase activity in L. saccharina (Korandová et al, ); however, the authors concluded that this failure could be explained either by a low amount of telomerase or by the presence of inhibitors of TRAP assays.…”

“…TTAGG‐specific telomerase activity was studied in a number of insect orders (Korandová, Krůček, Vrbová, & Frydrychová, ; Sasaki & Fujiwara, ). Distribution of this nucleotide sequence in insects is predominantly, but not universally, consistent with that of telomerase activity, and therefore suggests that the TTAGG‐telomerase system is functional in this group.…”

“…These contradictory results could be explained by a number of factors, e.g., the low amount of telomerase (Korandová et al, ). Also, the presence/absence of the TTAGG telomeric repeat coincides with the presence/absence of a candidate telomerase gene in several model insect species (reviewed in Robertson & Gordon, ).…”

The presence of the ancestral insect telomeric motif in kissing bugs (Triatominae) rules out the hypothesis of its loss in evolutionarily advanced Heteroptera (Cimicomorpha)

“…For example several insect groups do not exhibit this telomeric repeat, such as Diptera, Ephemeroptera, Odonata, Dermaptera, Siphonaptera, Mecoptera, Raphidioptera and parasitic Hymenoptera. In addition, Coleoptera, Neuroptera and Hemiptera orders include species with and without the ancestral (TTAGG) n telomeric motif (Frydrychová et al 2004, Gokhman et al 2014, Korandová et al 2014). In these insect groups, the ancestral telomeric motif is replaced by other alternative telomeric sequences such as (TCAGG) n in some coleopteran species (Mravinac et al 2011), non-(LTR)long terminal repeat retrotransposons in Drosophila Fallén, 1823 (Mason et al 2008), arrays of long satellite repeats in Culicomorpha dipteran (Walter et al 2001), or by unknown sequences as in damselflies, mayflies and some aphid species (Frydrychová et al 2004, Vítková et al 2005).…”

Telomere fusion in Drosophila: The role of subtelomeric chromatin

“…Most insect orders and species possess telomerase, although they can vary in sequence of the RNA component (TERC) used as template for telomeric DNA (see ref. 26 and references therein). Drosophila elongates its telomeres by transposon addition, and mosquitoes and chironomids rely on gene conversion of terminal satellite sequences for telomere maintenance.…”