ayout 1 - EMBL Grenoble

EMBL Research at a Glance 2009
Michael Knop
PhD 1995, University of
Stuttgart.
Postdoctoral research at the
MPI for Biochemistry, Munich
and the Beatson Institute for
Cancer Research, Glasgow.
Group leader at the MPI for
Biochemistry, Munich.
Group leader at EMBL since
2001.
Systems biology of meiosis and mating in
budding 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).
We mainly focussed on the processes that
regulate spore morphogenesis in comparison
to cell division by bud formation.
Among other things, 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.
Mating is another important aspect of the
life cycle of yeast. How do yeast cells 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 (fluorescence lifetime imaging, figure 2) to work with
yeast cells. These new quantitative imaging methods enable us to measure protein complex
formation and to visualise the activity of the MAP kinases. This yields important
new insights into the dynamics and the spatial organisation of the signalling process.
Future projects and goals
We continue to use quantitative microscopy approaches and subsequently expand our investigation to
three interconnected MAP kinase signalling pathways by using semi-high throughput screening microscopy
to quantify protein concentration, protein-protein interaction and protein localisation of all
the major components involved. We consider both quiescent and signalling conditions. The goal is to
enhance our understanding of the spatial and dynamic organisation of the signalling processes. This
will help us to derive and further develop quantitative models of the processes that regulate signalling
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-like
genomes that undergo yeast-like life cycles. Here we address the role of meiosis and recombination and
the impact of genome architecture on handling deleterious mutational load. 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 1: Electron micrograph of a forming spore. The
picture shows a spindle pole body (SPB) that is in
progress of forming a spore membrane.
2.2 Lifetime (ns) 2.6
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 not to 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.
Tau avg (ns)
Figure 2: High relative Fus3 MAP
kinase activity in the mating
projection (shmoo) of pheromone
stimulated yeast cells. Fus3 activity
was detected using FLIM (in
collaboration with Mark Hink and
Philippe Bastiaens).
Selected references
Maier, P., Rathfelder, N., Maeder, C.I., Colombelli, J., Stelzer, E.H.K.
& Knop, M. (2008). The SpoMBe pathway drives membrane bending
necessary for cytokinesis and spore formation in yeast meiosis.
EMBO J., 27, 2363-237
Maeder, C.I., Hink, M.A., Kinkhabwala, A., Mayr, R., Bastiaens, P.I. &
Knop, M. (2007). Spatial regulation of Fus3 MAP kinase activity
through a reaction-diffusion mechanism in yeast pheromone
signalling. Nat. Cell Biol., 9, 1319-1326
Maier, P., Rathfelder, N., Finkbeiner, M.G., Taxis, C., Mazza, M.,
Panse, S.L., Haguenauer-Tsapis, R. & Knop, M. (2007). Cytokinesis
in yeast meiosis depends on the regulated removal of Ssp1p from
the prospore membrane. EMBO J., 26, 183-52
Knop, M. (2006). Evolution of the hemiascomycete yeasts: on life
styles and the importance of inbreeding. Bioessays, 28, 696-708
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