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Telomere length compensation mechanisms as players in longevity and stress adaptation of insects
SÁBOVÁ, Michala
Telomeres are nucleoprotein structures at the ends of eukaryotic chromosomes that are important for genome stability and integrity. They are shortened with each cell cycle and during organismal aging. Although the most common telomere length compensation mechanism is the activity of a special reverse transcriptase, telomerase, in Drosophila telomeres are maintained by the retrotransposition of telomeric elements. In mammals, telomere length and telomerase activity can be influenced by lifestyle and the environmental conditions. This thesis is focused on activity of telomere length maintenance mechanism in insects in relation to aging and stress response.
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Effect of low doses of herbicide paraquat on antioxidant defense in Drosophila
SÁBOVÁ, Michala
Disruption of cell equilibrium between production of free radicals and antioxidant defence is named oxidative stress. The main component of antioxidant mechanism is activity of antioxidant enzymes, which include superoxide dismutase (SOD) and catalase. In this study we evaluated the effect of herbicide paraquat on response of SOD and catalase, their transcription level and locomotion activity in Drosophila melanogaster. We exposed the flies to a wide range of paraquat concentration. Our results revealed that transcript and enzymatic levels of both SOD and catalase have a similar biphasic dose response with the peaks at 2,5 ?M paraquat concentration, resembling hormetic effect. Then, males were more sensitive than females. However, females had an increased locomotion activity. We found that paraquat susceptibility is increased in males and mating flies. Therefore, this study supports hypothesis of stress sensitivity elevation as a physiological cost of reproduction.
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Transcriptional analysis of the \kur{HeT-A} retrotransposon in \kur{Drosophila melanogaster}
SÁBOVÁ, Michala
Instead of using telomerase, Drosophila melanogaster extends its telomeres by transposition of special telomeric retroelements (HeT-A, TART and TAHRE) targeted specifically to chromosome ends. One key step of the transposition mechanism is a transcription of the elements. Using the expression of a reporter Tomato transgene under HeT-A promoter control we obtained a spatial and temporal visualization of HeT-A promoter activity during the whole Drosophila development. This analysis confirmed that the activity of the HeT-A promoter is up-regulated by cell proliferation, however HeT-A promoter activity is not limited only to proliferating diploid cells. One important outcome of this study is the observation of variation in HeT-A promoter activity in both location and intensity.
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Genetic variability of natural populations of the \kur{Diuraphis noxia} (Aphididae)
SÁBOVÁ, Michala
Genetic variability of natural populations of the species Diuraphis noxia (Aphididae) was studied with RAPD method. First goal was to establish the chosen method in the laboratory and to optimize conditions of RAPD-PCR for D. noxia. This was followed by the pilot study, in which 12 populations were analyzed. Expected variability among individual populations and within population was acknowledged. The results of this investigation came up to the noted progress of diffusion of this species around the World. Results will be used in further more complex study of D. noxia.
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