Projects
of the
Küpper group
We are interested in the
physiology, biophysics and biochemistry (incl. molecular biology) of
photosynthetic organisms (green/brown/red algae, terrestrial and
submerged higher plants, cyanobacteria). Past and present research
projects deal(t) with the response of these organisms to abiotic and
biotic stress.
As shown
by
some sample graphs from our publications
below, our research mainly deals with mechanisms of active uptake of
metals (with hyperaccumulator plants as model organisms), mechanisms of
metal toxicity (in particular effects on photosynthesis), and
mechanisms of metal detoxification.
Some of these mechanisms are plant-specific (e.g.
inhibition of photosynthesis or detoxification by sequestration into
vacuoles), but many of them are very similar to mechanisms found in
animals (incl. humans). For example, all major families of metal
transporting proteins that are important in plants are found in
animals, and often in bacteria as well. In this way, analysing such
mechanisms in a plant model (e.g. using the natural overexpression of
metal transporters in hyperaccumulators), which is a major topic of our
research, is also directly relevant for understanding metal metabolism
in other groups of organisms, incl. humans. As an example, we
investigate the mechanism of function of metal transporting ATPases
from capturing the metal ions (number per cycle not known) out of the
solution on one side of the membrane and translocating them using
energy from ATP (coupling of the processes not yet known) to the other
side of the membrane, where they have to be released into solution
again by a so far unknown decrease of affinity of the binding site(s).
Further, we investigate how expression of such metal transport proteins
varies depending on physiological state and development of a tissue, we
investigate which ligands bind to the metals inside various cells and
cellular comparments, and with which kinetics and in which quantities
metals are sequestered into storage sites. In terms of toxicity, we
analyse in which sequence, in which causal relationship, in which metal
concentration range and under which environmental conditions (e.g.
irradiance) damage mechanisms occur that were proposed in previous
studies. This concerns in particular the much discussed oxidative
stress with consequences like protein oxidation and membrane damage in
comparison to the inhibition of the photosynthetic light reactions and
the Calvin cycle as well as the much-discussed genotoxicity. An
investigation of the time sequences, concentration dependence and
causal relationships is particularly important in the case of these
potential damage mechanisms because, in principle, they can strongly
influence each other. For example, a decreased efficiency of exciton
usage for photosynthesis can increase the formation of reactive oxygen
species. And the other way round, photosynthesis may become inhibited
as a consequence of oxidative damage to the thylakoid membranes and the
proteins involved in photosynthesis.
Although our research primarily aims at analysing
basic mechanisms of function, it is often closely related to practical
applications. For example, even today heavy metal toxicity is still a
major problem in many regions of the world - including middle Europe,
where e.g. Cu- and Zn-toxicity is often caused by the agricultural use
of Cu und Zn containing pesticides. In addition, metal refineries and
abandoned hazardous sites in former and current industry cause such
environmental problems. Thus, our research on mechanisms of toxicity is
combined with investigations of toxicity in heavy metal contaminated
habitats. Further, hyperaccumulator plants, which naturally use an
active accumulation of heavy metals in their above-ground tissues as a
defence against herbivores and pathogens, are already successfully used
for biotechnological detoxification ("phytoremediation", especially of
Cd) and for commercial extraction of metals ("phytomining", important
mainly for Ni).
In our projects, we do not only use various
terrestrial and aquatic species of higher plants, but also
microorganisms (algae and cyanobacteria). First, we use such organisms
as models for specific experiments that investigate general questions
that are relevant for higher plants and possibly animals but that are
difficult to analyse with such "higher" organisms. This applies e.g. to
questions concerning the ecotoxicology of heavy metals. In addition, in
recent years (since 2001) the investigation of the regulation of
photosynthesis for nitrogen fixation in cyanobacteria has become an
independent part of our research.
For these investigations, we also developed methods
of our own, e.g. the "Fluorescence kinetic Microscope" (FKM), a chamber
for measuring photosynthesis and oxygen evolution of filamentous algae,
quantification of pigments in complex mixtures by Gauss-Peak-Spectra
(GPS), quantitative mRNA in situ hybridization
Key methods applied in our projects involve (in
our
and collaborating labs):
(1) Spectroscopy:
(a) UV/Vis- absorbance and fluorescence spectroscopy, with
special emphasis on the analysis of chlorophyll fluorescence kinetics,
microscopic (single-cell, time-resolved and in vivo) spectroscopy and pigment
analysis in complex mixtures
(b) X-ray spectroscopy: energy dispersive x-ray emission microanalysis
(EDXA), x-ray absorption spectroscopy (XANES, EXAFS);
(c) elemental analysis (ICP-AES, ICP-MS, AAS)
(2) Microscopy:
(a) light microscopy: spatially and spectrally resolved fluorescence
kinetic microscopy
(to study biophysics of photosynthetis and metal trafficking); confocal
microscopy for quantitative mRNA in
situ hybridisation; classical
transmission and fluorescence microscopy
(b) SEM: energy dispersive x-ray microanalysis (EDXA) of bulk-frozen
samples and
dried samples from micropipettes
(3) Molecular biology:
quantitative mRNA in situ
hybridisation, Western Blotting
(4) Preparative work:
FPLC,
HPLC;
gel electrophoresis; isolation and work with protoplasts;
single-cell sap sampling with
picolitre-pipettes
Heavy metals in plants
|
Mechanisms
of
heavy
metal stress
|
 
 
 
|
Mechanisms
of
heavy
metal resistance and hyperaccumulation
|
 
 
|
Regulation of photosynthesis
|
Regulation
of
photosynthesis
for nitrogen fixation in cyanobacteria
|
|
Photosynthetic
oscillations
|
|
Development of methods and scientific
instruments
|
The
Fluorescence kinetic
Microscope
(FKM)
and
Chambers for
physiological measurements under the microscope
|
 2007
 June
'09
|
Chamber
for
measuring
photosynthesis
and oxygen evolution of filamentous algae
|
|
Quantification
of
pigments
in
complex mixtures by Gauss-Peak-Spectra (GPS)
|
|
Quantitative
mRNA
in
situ hybridisation
|
|
designed by Hendrik Küpper, last
modified 31 August 2011
|
