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Trade-offs in parasitoid resistance and competitive ability in Drosophila
SIDWELL, Jeni
Trade-offs in fitness traits in Drosophila were studied in a laboratory environment. Fly and wasp lines originated from an ecological community in a tropical rainforest in Queensland, Australia and were established in České Budějovice. Experimental evolution was used to impose selective pressures on populations of flies to select for parasitoid resistance and competitive ability. The selection regimes were followed by two separate phenotyping experiments to measure the resulting phenotypic changes and impose novel conditions to the evolved flies in order to identify trade-offs.
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Mechanisms structuring host-parasitoid communities in a global warming perspective
THIERRY, Mélanie Jeanne
Ecological communities are composed of a multitude of interacting species, and the outcome of pairwise interactions depends on other co-occurring species within the community. With current global environmental changes, both abiotic and biotic environment are changing, affecting the structure and dynamics of communities. I used a series of laboratory experiments on a set of Drosophila species and their parasitic wasps to investigate the effects of biotic and abiotic factors on interactions and communities. I first compared the outcome of host-parasitoid interactions across community modules commonly found in host-parasitoid communities (i.e., pairwise interaction, exploitative competition, apparent competition, and both exploitative and apparent competition). I found generally higher host suppression with multiple parasitoid species, but species-specific effects for parasitoid performance. I then observed that warming impacts host communities through direct effects on species performance rather than altered competitive interactions and parasitism. Finally, I found that temperature strongly influences the effects of multiple parasitoids on host suppression across different parasitoid assemblages, suggesting a general pattern for the environmental dependence of trophic and non-trophic interactions. My thesis emphasizes the importance of considering environmental factors and different interaction types to better predict community dynamics in a rapidly changing world.
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Biotic, abiotic and symbiotic factors that influence a host-parasitoid food web
BROWN, Joel James
The aim of this thesis was to investigate the deterministic patterns of insect-associated microbiome community composition and to investigate the role of symbiotic bacteria in insect model systems. I have shown that life stage is a key factor influencing microbiome composition, in both holometabolous and hemimetabolous insects, in addition to host species identity and local environment. I was able to find these deterministic patterns by controlling for diet in field studies of microbiomes, which is a well-known influential factor of microbiome communities. My thesis emphasises the importance of investigating the taxonomic and functional diversity of insect microbiomes and including symbiotic microbes in community level studies.
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Expression and purification of adhesive recombinant proteins, sericin 2 and salivary gland secretion 3
VU, Trang Thanh
Recombinant proteins derived from Bombyx mori Ser-2 gene and Drosophila melanogaster Sgs3 gene were expressed in bacterial expression systems, purified and partially characterised. The identity of the expressed recombinant proteins was verified by mass spectroscopy. The recombinant proteins were tested for their ability to coat hydrophobic surfaces and sequentially serve as a substrate for the attachment of cells in tissue culture. The quality of the recombinant protein surface coating was examined by scanning electron microscopy. The results show that further optimisation for the purification, solubilization and refolding of these recombinant proteins is needed to incorporate their potential as biomaterials in the future.
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Characterisation of \kur{Drosophila melanogaster} mutated for all genes of the Sirtuin family
PEKÁČOVÁ, Aneta
The aim of my study was to create a Drosophila line lacking the expression of all Sirtuin genes, check its developmental phenotype and characterise its response in stress conditions. The flies had bigger weight than controls, they had decreased fertility and fecundity and they developed more slowly. They showed a trend towards increased resistance to chill coma, but they did not show a significant difference in starvation or oxidative stress assay. Its effect on lifespan is being investigated.
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Study of adipokinetic hormone role in insects stressed by entomopathogenic nematodes
IBRAHIM, Emad Ahmed Sayed
In this thesis, the effect of infection elicited by entomopathogenic nematodes (EPNs) Steinernema carpocapsae on Pyrrhocoris apterus and Drosophila melanogaster models were evaluated, and a role of adipokinetic hormones (AKHs) during the infection was characterized. These were monitored by determination of mortality, and various biochemical and physiological characteristics such as AKH levels both in the central nervous system (CNS) and in hemolymph, AKH gene expression in CNS, level of anti-oxidative stress markers, general metabolism and level of nutrients in normal and genetically modified insects. At P. apterus the mortality tests revealed that application of AKH increases the efficacy of EPN treatment. This result was confirmed using the firebugs with AKH receptor deficiency. Further, the increase of AKH expression and AKH levels in CNS and hemolymph seemed to be coordinated after the nematode treatment. At the D. melanogaster model also, the effect of adenosine into the above-mentioned characteristics was included. For this, mutants in AKH (AHK1), adenosine receptor (AdoR1) genes, and in both these genes together (AHK1 AdoR1 double mutant) were employed. Altogether, the results confirmed the involvement of AKH, and partially also adenosine into the antistress defense reactions elicited by the nematobacterial infection. Finally, the last part of the study was focused on examination of the vitellogenin (Vg) role in the defense reaction in firebug body P. apterus affected by two entomopathogenic organisms, the nematode S. carpocapsae and the fungus Isaria fumosorosea. The results revealed that Vg proteins play an important role in the defense against both types of the infections and are also able to kill entomopathogenic bacteria Xenorhabdus nematophila, that are symbionts of S. carpocapsae and that increase toxicity of this nematode.
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Role of IDGFs and adenosine signaling in cell survival and energy homeostasis
BROŽ, Václav
Two groups of growth regulators were described in Drosophila imaginal disc cell culture Cl.8+. Imaginal disc growth factors (IDGFs) belonging to chitinase-like protein family of carbohydrate binding proteins and Adenosine deaminase-related growth factors (ADGFs), which are active adenosine deaminases influencing homeostasis of key cellular metabolite adenosine. The functions of two of the IDGFs, as well as the effects of extracellular adenosine and its receptor were studied primarily in in vitro cell culture. Our results supported their roles in the regulation of cell survival and energy homeostasis especially in imaginal disc cells. Both the IDGFs and adenosine also play important roles in organismal responses to stress and infection and may interact in vivo.
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