The confused flour beetle, Tribolium confusum A model for investigating Wolbachia-host interactions
by Yeganeh Gharabigloozare
Date of Examination:2022-05-03
Date of issue:2022-07-20
Advisor:Prof. Dr. Christoph Bleidorn
Referee:Prof. Dr. Gregor Bucher
Referee:Prof. Dr. Elvira Hörandl
Persistent Address:
http://dx.doi.org/10.53846/goediss-9301
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Abstract
English
Summary Wolbachia, a group of maternally inherited intracellular endosymbiotic Alphaproteobacteria, are found in a wide range of arthropods and nematodes. It has been estimated that over 65% of insect species are infected with at least one Wolbachia strain. A major proportion of global biodiversity is represented by insects, and that a single symbiont can infect half of the presented species in the world shows how extraordinarily successful Wolbachia is. However, while Wolbachia is well known as a manipulative reproductive parasite specially by inducing cytoplasmic incompatibility, they are also significant regulators of host fitness by distributing in somatic tissues as well. Therefore, their role in host biology and physiology is undeniable. It has been suggested that more than 30% of Drosophila stocks, a ubiquitously used model system, are infected with these intracellular bacteria, Wolbachia, which also illuminates their fundamental role in evolutionary studies. In addition, some Wolbachia strains help to protect their insect hosts against viral infections, and their antiviral effects have been utilized as a biocontrol tool to inhibit the transmission of some viruses, related to human infections. Not surprisingly, Wolbachia also attract a great interest of biologists, since they may apply as a novel environment friendly agent to control insect pest species. Species of the flour beetles genus Tribolium are small darkling beetles, two of which, T. castaneum and T. confusum, are the most notorious global pests of flour mills and stored food products, but at the same time are widely used as model organisms in fields of evolution, genetics and development. Consequently, adapting Tribolium beetles as a model system for Wolbachia research next to the widely used classical model systems such as Drosophila flies, Culex mosquitoes and nematodes, opens possibilities for a wide range of studies, taking advantage of the already established culturing methods and genetical tools. Regarding Wolbachia-host association, T. confusum is known to be naturally infected with endosymbiont bacteria, Wolbachia. Surprisingly, research infrastructure of Wolbachia-host interaction in T. confusum is considerably less established than other models, even though the number of such studies is recently growing. In order to contribute to the potential role of T. confusum beetles in host symbiosis relationship, we outlined the potential of establishing T. confusum as a model for Wolbachia research, assembled and annotated genome of the Wolbachia strain (wTcon), investigated the fitness effects of wTcon in relation to temperature in an experimental approach and performed behavioral studies to investigate the influence on the locomotion and action selection of Tribolium confusum beetles. Hereby, we confirmed that the wTcon genome is sharing the characteristics as the other Wolbachia strains and especially the ones in supergroup B. Also, we showed that wTcon is temperature specific and the density of the endosymbiont reduces under heat stress, although the cytoplasmic incompatibility (CI) was intact. In addition, we observed that Wolbachia infection alters the locomotion of T. confusum beetles, so as to increase the wTcon transmission in the host population.
Keywords: Tribolium confusum, Wolbachia, Cytoplasmic incompatibility