Analysis of embryonic development in Tribolium castaneum using a versatile live fluorescent labelling technique

Change log

Studies on new arthropod models are shifting our knowledge of embryonic patterning and morphogenesis beyond the Drosophila paradigm. In contrast to Drosophila, most insect embryos exhibit the short or intermediate-germ type and become enveloped by extensive extraembryonic membranes. The genetic basis of these processes has been the focus of active research in several insects, especially Tribolium castaneum. The processes in question are very dynamic, however, and to study them in depth we require advanced tools for fluorescent labelling of live embryos. In my work, I have used a transient method for strong, homogeneous and persistent expression of fluorescent markers in Tribolium embryos, labelling the chromatin, membrane, cytoskeleton or combinations thereof. I have used several of these new live imaging tools to study the process of cellularisation in Tribolium, and I found that it is strikingly different to what is seen in Drosophila. I was also able to define the stage when cellularisation is complete, a key piece of information that has been unknown until now. Lastly, I carried out extensive live imaging of embryo condensation and extraembryonic tissue formation in both wildtype embryos, and embryos in which caudal gene function was disrupted by RNA interference. Using this approach, I was able to describe and compare cell and tissue dynamics in Tribolium embryos with wild-type and altered fate maps. As well as uncovering several of the cellular mechanisms underlying condensation, I have proposed testable hypotheses for other aspects of embryo formation. The work presented in this thesis will serve as a foundation for future studies on cellularisation and tissue morphogenesis in Tribolium. Furthermore, the live imaging method, the fluorescent labelling constructs, and the analysis I carried out should be easily adaptable to other non-model arthropod species.

Akam, Michael
Development, Morphogenesis, Tribolium, Embryo, Patterning
Doctor of Philosophy (PhD)
Awarding Institution
University of Cambridge