|
| |
|
|
Anti-oxidative stress response in Drosophila melanogaster - The role of adipokinetic hormone and adenosine
ZEMANOVÁ, Milada
In this thesis, the phenomena of the oxidative stress (OS) and anti oxidative stress responses in insects are described in a comprehensive review, and the outcomes of the experimental work are presented. The focus of the work was on defence reactions and their putative control by the adipokinetic hormone (AKH) and adenosine in the Drosophila melanogaster model. For this purpose, we studied the effect of the paraquat (oxidative stressor) treatment on adult flies and larvae carrying mutations in Akh (Akh1) and adenosine receptor (AdoR1) genes, and in both these genes together (Akh1 AdoR1 double mutant). The initial mortality tests revealed the double mutant Akh1 AdoR1 was more sensitive to OS than either of the single mutants. The AKH synthesis under the OS condition seems to be out of the gene expression control, since the increase of an AKH amount in CNS was not linked with the stimulation of Akh gene expression after a paraquat treatment. Further, the gene expression of the antioxidant enzyme glutathione S transferase D1 (GstD1) increased rapidly with OS, though the enzyme activity increased negligibly regardless of both the OS and mutations. Interestingly, the relative expression of GstD1 gene was minimal in the double Akh1 AdoR1 mutant; thus, it was concluded that both AKH and adenosine are employed in the GstD1 gene expression control. Similarly, AKH and adenosine seem to act in tandem in glutathione (GSH) regeneration, since the GSH level was significantly lower in all untreated deficient flies with the maximal effect in the Akh1 AdoR1 double mutant; accordingly, the reduction in the GSH level was enhanced by paraquat treatment. Altogether, the important roles of both AKH and adenosine in the anti oxidative stress response in D. melanogaster were demonstrated.
|
|
|
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.
|
|
|
Efekt ADGF-A RNAi na imunitní odpověď \kur{Drosophily melanogaster} po infekci parazitickou vosou
ŠNEBERGEROVÁ, Pavla
In previous studies the extracellular adenosine has been proved as an important signaling molecule controlling dynamics of the immune response in Drosophila melanogaster. In mammals the adenosine signaling and control is more complex process. Since there is a certain genetic and evolutionary conservation between mammals and invertebrates, Drosophila represents simple system how to study such a complex regulation in vivo. Mutations of adenosine receptor in all cells as well as downregulation of ENT2 in immune cells caused decrease of resistance of the immune system against Drosophila parazitoid. The aim of the thesis is to determine whether RNAi targeted against mRNA of adenosine deaminase ADGF-A, which degrades e-Ado under natural conditions, would have any effect on immune response.
|
|
|
Analýza promotorových sekvencí telomerického elementu \kur{HeT-A} u \kur{Drosophila melanogaster}
ŠVELLEROVÁ, Hana
Drosophila melanogaster extends its telomeres by transposition of special telomeric retroelements (HeT-A, TART and TAHRE) targeted specifically to chromosome ends. Retroelement HeT-A is the most studied of telomeric elements and recent studies revealed significant sequence variability of the element HeT-A, not only along its length but also in areas with regulatory activity. This thesis is focused on the activity of different HeT-A promotors during the whole Drosophila development and comparision of transgenic lines with HeT-A promotor and reporter Tomato transgen and it was confirmed the sequence variability of the promotor HeT-A element and its tissue and organ specificity.
|
|
|
Role adipokinetic hormone in fruit fly \kur{Drosophila melanogaster}
KUTHANOVÁ, Michaela
The aim of the thesis was evaluation of the adipokinetic hormone (AKH) effect on the fruit flies Drosophila melanogaster with AKH production deficiency, and adenosine receptor dysfunction. A nutrition level was measured in those flies to evaluate involvement of AKH and adenosine into the metabolic pathways. Results revealed that application of external Drome-AKH significantly increased the free glycide level in the fly bodies. On the other hand only limited effect of hormonal treatment on other nutrients (lipids, proteins) was recorded. The role of adenosine was unclear, but its involvement cannot be excluded.
|
|
|
Mode of action of adipokinetic hormone at the sub-cellular level in potentiating anti-oxidative responses in insects.
BEDNÁŘOVÁ, Andrea
Adipokinetic hormones (AKHs) are neuropeptides from the arthropod AKH/RPCH (adipokinetic hormone/ red pigment concentrating hormone) family. The typical AKH is an octa-, nona- or decamer that is synthesized, stored and released by the neurosecretory cells of the corpora cardiaca (CC) connected to the brain and primarily involved in the mobilization of energy reserves from the fat body in insects. In addition to its well established role in energy metabolism, AKH has also been implicated to be involved in stress responses specifically to oxidative stress. Oxidative stress induced elevation of AKH levels as well as a modulation of biomarkers of oxidative damage following exogenous application of AKH have been demonstrated. However, the discrete steps involved in the mode of action of AKH in triggering an anti-oxidative response is far from clear. Given the role of AKH as a neuroendocrine factor that mediates a response to oxidative stress, the mode of action of AKH at the sub-cellular level was investigated. Using isolated central nervous system (brain) as an in vitro model, we establish that AKH can potentiate an anti-oxidative response to oxidative stress. Further, we also demonstrate that AKH uses a conserved signal transduction mechanism involving both protein kinase C (PKC) and cyclic adenosine monophosphate (cAMP) and by mobilizing both intra as well as extra-cellular Ca2+ stores to elaborate its anti-oxidative response. Finally, using the genetically tractable fruit fly Drosophila melanogaster, we demonstrate through RNAi mediated knockdown of AKH synthesis as well as overexpression of AKH using the GAL4/UAS system, that the fork-head box transcription factor (dFoXO) might function downstream of AKH signaling in its stress responsive role. These results implicate AKH as a stress hormone while offering possibilities to further identify specific regulatory mechanisms and downstream effector molecules. Since stress signaling pathways are conserved, insights obtained from such studies on insects will offer some unique avenues for understanding stress responses and related pathologies in vertebrates including humans.
|
|
|
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.
|
|
| |
|
|
Use of \kur{Notch} gene for the production of genetic "sexing" lines of codling moth.
ŠVELLEROVÁ, Hana
The codling moth, Cydia pomonella, is the key pest of pome fruit and walnut orchards in the temperate regions of the world. The extensive use of insecticides for a control of this pest has resulted in the development of resistance to these chemicals, and there is an increasing demand on the use of environment-friendly control tactics, such as the Sterile Insect Technique (SIT). Codling moth SIT relies on the mass rearing and release of genetically sterile both males and females into a wild population. However, male-only releases could significantly reduce costs of the mass rearing and increase SIT efficiency. In this thesis I focused on the use of a temperature-sensitive mutant allele of the Notch gene for production of genetic "sexing" lines of codling moth.
|
guest ::
