Dokument 1.pdf - OPUS - Friedrich-Alexander-Universität Erlangen ...

Summary
Summary
Tribolium castaneum is an outstanding model for comparative developmental bi-
ology and is well on the way to become an important system for Insect biology in
general. This is largely due to its amenability for systemic RNA interference, allowing
straightforward functional studies.
In the first chapter of this thesis I used these techniques to analyze the function of
the posterior group genes nanos and pumilio in early embryonic patterning of Tri-
bolium. In the second chapter I present the development and testing of a procedure
using RNAi for a genomewide screen to identify new developmental gene functions.
In the long germ insect Drosophila, localized polarity cues serve as starting points
for the antero-posterior regionalization of the embryo. The posterior to anterior
NANOS gradient is part of this system and – in concert with PUMILIO - crucial for the
formation of abdominal segments. To elucidate to which degree this system is con-
served in short-germ embryogenesis, I analyzed nanos and pumilio function in Tri-
bolium. I could show that both genes are indeed involved in abdomen formation in
Tribolium as well. However, this is apparently not due to a role in blastodermal re-
gionalization, but related to an interaction with the terminal system. In addition, I
found an effect of nanos and pumilio on the formation of anterior segments. This
unexpected influence on head patterning appears to be mediated by an impact on
the formation of anterior Gap-Gene expression domains. Thus, the function of Tri-
bolium nanos and pumilio differs from their Drosophila orthologs, which may be due
to the special needs of short germ development.
The candidate gene approach, which has been very successful throughout the
last decade, is conceptually limited for the in depth analysis of Tribolium biology. To
overcome these limitations and to further transform Tribolium into a primary model of
basic insect research, the German Tribolium community is initiating a genomewide
RNAi screen: iBeetle. In the second part of my thesis, I present the development of
the iBeetle screening procedure, which allows rapid and efficient screening of gene
functions for embryonic and postembryonic developmental processes, ranging from
embryonic axis formation to the development of odoriferous glands.
To test this concept, I designed and performed a pilot-screen, which demon-
strated that important developmental genes can be detected with high sensitivity and
that the approach is suitable to reveal unknown gene function with high frequency.
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