Meiosis - where Cell Biology meets Evolution
Mating - where Yeast meets Yeast
Previous
and current research
Our group is interested in the various cellular processes
that underlie the sexual cycle of budding yeast [mating and
meiosis]. In the past we have addressed the meiosis
specific pathways that regulate spore morphogenesis with
respect to spindle pole body function, membrane formation
and morphogenesis and cytokinesis (Figure
1
and
Figure 2).
We mainly focused on the processes that regulate spore
morphogenesis in comparison to cell division by bud
formation. Among others, we concentrated on the regulation
of spindle pole function in controlling vesicle fusion and
in the initiation of spore morphogenesis and on membrane
shaping of the spore.
Figure 1
The
spore assembly pathway of yeast.
more...
Figure 2
This
picture shows a cell in meiosis II in the progress of
forming 2 spores (yellow), which relies on the selective
activation of 2 spindle pole bodies (green).
more ...
Mating is another important aspect of the life cycle of
yeast. How do yeast cells faithfully find a mating partner?
We study the MAP kinase signal transduction pathway that
underlies signal transduction during mating. We established
Fluorescence (Cross-) Correlation Spectroscopy
[FCCS]
and FLIM (Figure
3)
to work with yeast cells (->Ref).
These new quantitative imaging methods enable us to
measure protein complex formation and to visualize the
activity of the MAP kinases. This yields important new
insights into the dynamics and the spatial organization
of the signaling process.
Figure 3
High
Fus3 MAP kinase activity in the mating projection of
pheromone stimulated yeast cells. Fus3 activity was
detected using FLIM (in collaboration with Mark Hink and
Philippe Bastiaens).
See our publication (Maeder et al.,
2007)
and the
press release.
Future
projects and goals
We continue to use quantitative microscopy approaches and
subsequently expand our investigation to 3 interconnected
MAP kinase signaling pathways by using semi-high throughput
screening microscopy to quantify protein concentration,
protein-protein interaction and protein localization of all
the major components involved. We consider both, quiescent
and signaling conditions. The goal is to enhance our
understanding of the spatial and dynamic organization of
the signaling processes. This will help us to derive and
further develop quantitative models of the processes that
regulate signaling through theses pathways.
Our work on meiosis has gradually shifted to questions that
relate to the role and function of genome recombination in
meiosis. As a model, we use computer simulations of
population of yeast-alike genomes that undergo yeast-alike
live cycles (->Ref).
Here we address the role of meiosis and recombination
and the impact of genome architecture on handling
deleterious mutational load (Figure
4).
To complement these approaches, we use yeast as a model
for experimental evolutionary studies where we address
the consequences of random mutations on fitness, and on
the role of meiosis and recombination to purge
deleterious load.
Figure 4
Evolution
is fueled by mutations. Sexual cycles (mating and meiosis)
constitute processes that enable efficient handling of good
(beneficial) and bad (deleterious) mutations.
Furthermore, we study a novel yeast species with similar
live-cycle properties as
S. cerevisiae,
but which has one notable and most interesting difference:
this species appears to not recombine its genome during
meiosis. We use genome sequencing and experimental
approaches to address how this species performs meiosis I
and to understand the impact of absent recombination on the
evolution of the genome.