Characterization of TTAGG telomeric repeats,their interstitial occurrence and constitutively active telomerase in the mealybug <Emphasis Type="Italic">Planococcus lilacinus</Emphasis> (Homoptera; Coccoidea) |
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Authors: | Kommu Naga Mohan B Sandya Rani Pooja Swaroop Kulashreshta Jayarama S Kadandale |
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Institution: | (1) Centre for Human Genetics, Biotech Park, Next to Aravind Mills, Bangalore, 560100, India |
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Abstract: | We confirmed the occurrence of the insect TTAGG telomeric repeats in the mealybug Planococcus lilacinus, a radiation-resistant coccid, by single primer polymerase chain reaction (PCR) and Southern hybridization. Analysis of Bal31 nuclease-digested DNA by Southern hybridization and chromosomes by FISH suggests that these repeats occur mainly at the
ends of the chromosomes. However, sequence analysis of the PCR products of TTAGG-associated sequences from genomic DNA showed
their interstitial occurrence and association with certain unrelated low-copy repeats. Because of their shorter length, the
interstitial TTAGG sequences were detectable by primed in situ hybridizations but not by FISH. Analysis of chromosomes recovered
after irradiation by fluorescent in situ hybridization suggested acquisition of TTAGG repeats at a majority of the healed
ends. We also observed mild telomerase activity in unirradiated insects which was further enhanced after irradiation. Taken
together, these results suggest that the mealybug has an efficient mechanism of formation of TTAGG repeats at radiation-induced
chromosome ends and constitutively active telomerase may be a feature associated with rapid recovery of chromosome ends damaged
by ionizing radiation. |
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