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KU Leuwen (2013)

Regulation of RNA interference in the desert locust, Schistocerca gregaria

Wynant, Niels

Titre : Regulation of RNA interference in the desert locust, Schistocerca gregaria

Auteur : Wynant, Niels

Université de soutenance : KU Leuwen

Grade : Doctor in de Wetenschappen : Biochemie en biotechnologie (Leuven) 2013

RNA interference (RNAi) is a natural gene silencing mechanism that is triggered by double stranded (ds)RNA. Whereas RNAi is an essential endogenous process of regulating gene expression, it has also become a widely used research tool to knock down and analyse the function of genes in eukaryotes. In addition, several recent studies have shown that RNAi may also contribute to strategies for selectively controlling agricultural pests, including a number of insect species, and might serve to protect beneficial and vector insects against viral infections. Yet, for these purposes, the organism should display systemic (sys)RNAi, a phenomenon that is characterized by the fact that injection or oral delivery of dsRNA induces gene silencing effects throughout the body. SysRNAi-responses were first described in the nematode Caenorhabditis elegans, where individual cells have the ability to take up extracellular dsRNA. For other organisms, such as the insect model organisms Drosophila melanogaster and Bombyx mori, as well as all mammalian species investigated, injection of dsRNA does not result in potent gene-silencing effects. Yet, several recent studies have illustrated that sysRNAi displays a strong inter-species variation in insects. In this PhD-thesis, we demonstrate that the desert locust, Schistocerca gregaria, displays a highly sensitive and robust RNAi-response upon injection of dsRNA into its body cavity. Moreover, we present S. gregaria as an interesting model to study the regulatory mechanisms of sysRNAi in insects, since the RNAi-efficiency in these locusts varies between different tissues and S. gregaria is less sensitive towards orally delivered dsRNA. In a second part of our research, we have identified factors contributing to the tissue-dependency and the distinct RNAi-susceptibility upon injection and oral delivery of dsRNA. Furthermore, regarding the fact that cellular import of dsRNA is a prerequisite for sysRNAi, we identified a functional RNAi-transport route in S. gregaria. Taken together, the data presented in this PhD-thesis significantly improve our knowledge on the regulatory mechanisms of RNAi in the desert locust and might contribute to the development of new methods to enhance the (sys)RNAi-susceptibility in less-responsive insect species.


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