Kitzmann, Peter

English

Natural selection and the struggle for ecological niches were the driving force for the origin of a tremendous number of animal groups with different body shapes. The segmental organization of insects enhanced their evolutionary specialization. Adaptations led to different morphologies, for instance with respect to the head. The head, which carries the feeding apparatus and the main sensory centers enabling interaction with the environment, is one prerequisite for evolutionary success. The segmental structure of the insect head facilitated evolution of adaptations with respect to morphology. However, although the head is of great importance for the evolutionary success, there is no comprehensive understanding of the gene network regulating anterior head development until now. Furthermore, the genetic basis for the different insect head morphologies is unknown. Moreover, there are open questions concerning the segmental structure of the head and how morphogenetic movements lead to the adult head. 
During the last years the red flour beetle Tribolium castaneum was developed as a major model organism for studying insect head development. Recent studies were able to successively uncover the genetic interactions of anterior head development. However, so far the gene set and its interaction are not comprehensively unraveled. Tc-foxq2 is a novel regulator of head development identified with a highly specific head phenotype in the iBeetle screen. Hence, I studied its potential function in the anterior head gene regulatory network. Another open question is the contribution of the different embryonic head regions to the adult head. To provide new insights regarding this question I wanted to provide new features for the Tribolium toolbox.
In this study I was able to show that Tc-foxq2 is specifically expressed in the anterior pre-segmental head region, similar to the conserved expression pattern, which is located at the anterior pole in metazoan species. Further, I was able to show that Tc-foxq2 is an upstream player within the anterior head gene regulatory network, forming a conserved patterning unit together with Tc-six3. Tc-foxq2 knock-down results in an increased cell death rate within the clypeo-labral region, which consequently leads to reduced labral buds at embryonic stages. This defect is also reflected in L1 larval cuticles showing a labrum that is strongly reduced or completely absent. Further, using neurogenic in vivo imaging reporter lines I was able to show that embryonic knock-down of Tc-foxq2 function leads to central body and mushroom body defects. Moreover, I was able to generate new reporter lines that drive expression of the chimeric H2Av::EGFP nuclear marker protein under control of the Tc-αTubulin1 promoter or the Tc-ribosomal protein subunit3 promoter. I analyzed the lines with respect to localization of the marker protein, signal distribution within the embryo, signal intensity in different developmental stages and tissues, and viability of the different transgenic lines. I could show that the lines are functional and that the Tc-αTubulin1 promoter line is best suited for being analyzed with light-sheet imaging. Finally, I was able to generate and to show functionality of new in vivo imaging lines for laser-induced cell marking and genetic cell marking

Georg-August-University Göttingen

Morphogenesis and Genetic Regulation of the Insect Head

https://ediss.uni-goettingen.de/bitstream/11858/00-1735-0000-002B-7C11-E/1/Ph.D.%20Thesis%20-%20Peter%20Kitzmann.pdf

Morphogenesis and Genetic Regulation of the Insect Head

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Georg-August-University Göttingen