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Research report:
Plant Physiology and Photobiology AG Galland

Prof. Dr. Paul Galland
Born March 26 1948
1971 Diploma, University Freiburg i.Br.
1975 Ph.D., University Freiburg i.Br.
1982-1987 Research Assistant professor,Syracuse University N. Y.
1988 Habilitation, University Marburg
C3-Professor for Plant Physiology, University Jena
C4-Professor for Plant Physiology and Photobiology in Marburg


Franz Grolig
Born February 08 1956
1983 Diploma, University Giessen
1986 Ph.D., University Giessen
1987 Visiting FelIow , Plant Cell Biology Group, Research School of Biological Sciences, Australian National University, Canberra
1988-94 Associate Professor, University Giessen
1995-97 Visiting FelIow, UniversityGiessen and Biocenter, Frankfurt
1998-2001postdoc, University Marburg
2002Senior sientist, Plant Physiology and Photobiology, University Marburg


Main research
projects:





Blue- and red-light reception


In the fungal and plant kingdoms numerous processes of movement and development are regulated by near-UV and blue light. The requisite blue-light receptors are flavoproteins whose photochemical primary responses and associated signal transduction chains are known only in part.

In our group we employ three model systems, the crucifer Arabidopsis thaliana, the coleoptile of Avena sativa and the sporangiophore (fruiting body) of the single-celled zygomycete fungus, Phycomyces blakesleeanus. We are particularly interested in those physiological functions of the signal transduction chain that occur at the level of the photoreceptor.

In this context we direct our efforts at the identification of the photochemical primary reactions. In physiological and genetic studies we could show that fundamental functions such as wavelength discrimination, sensitivity as well as dark- and light-adaptation are processed at the level of the blue-light receptors.

Fig1galland

Figure 1: Phototropism of the sporangiophore (fruiting body) of the zygomycete, Phycomyces blakesleeanus (photograph by D.S. Dennison).


To detect photoprimary reactions of the requisite receptors we employ in-vivo rapid-scan spectroscopy (Schmidt 2004a,b) and fluorescence spectroscopy. With these methods we were able to detect in sporangiophores of Phycomyces blue-light elicited absorbance changes that indicate the formation of flavosemiquinones (half-reduced flavin radicals). These flavosemiquinones must be generated by the blue-light photoreceptors, because they are absent in photoreceptor mutants.

The semiquinones absorb beside near-UV and blue light also green and yellow light and they can thus explain a number of photophysiological responses that are elicited by long-wavelength light and that had remained unexplained in the past. By employing in-vivo fluorescence spectroscopy we obtained further evidence for the formation of flavosemiquinones upon blue-light absorption. Our physiological investigations indicate that the blue-light receptor(s) of Phycomyces undergo upon light absorption a reduction to the semiquinone radical (Galland and Tölle 2003).

The role of flavosemiquinones in blue-light perception is further investigated in Arabidopsis thaliana. Cryptochromes 1 and 2 of this plant contain as chromophores tetrahydrofolate and FAD, and irradiation of isolated cryptochrome generates flavosemiquinone radical (FADH). Presently it is, however, unknown whether or not the flavosemiquinone plays a role in the photoreception of Arabidopsis. Our own investigations indicate that this is indeed the case and that the semiquinones enable Arabidopsis to react to green and yellow light.



Graviperzeption


Plants and fungi require light and gravity as environmental cues to orient in space (Corrochano and Galland, 2006). The vector of earth acceleration is detected by heavy cell inclusions, so-called statoliths, that function as gravisusceptors. In plants these are generally amyloplasts in gravisensitive tissue, i.e. statenchyms. The gravireceptors proper have not been identified yet. We are interested in graviperception and in the mechanisms by which light and gravistimuli interact. In this context we focus on the (fast) primary responses that are associated with graviperception (Werner Schmidt) and also on the cytoskeleton (Franz Grolig).

For the sporangiophores of Phycomyces we have identified the statoliths of gravitropism. These are octahedral protein crystals that occur in the central vacuoles of the sporangiophore. The crystals are associated with pterin- and flavin-like pigments that exist largely in the reduced state. In addition to the octahedral protein crystals sporangiophore possess also other organelles that play a prominent role in graviperception. These are apical lipid globules that form a lose complex hold together in a cage of actin filaments. Upon reorientation of the sporangiophore the lipid globules are displaced, i.e. they float "upward". The fact that the gravitropic bending correlates with the number of apical lipid globules indicates that they play an essential role in graviperception (Grolig et al. 2004). The lipid globules represent a novel type of gravisusceptors, i.e. "buoys", that possess a lower specific weight than the surrounding cytoplasm. Even though the existence of such "buoys" had been predicted for many years, they have remained elusive in plants. Microirradiation of the lipid globules has shown that they may also play a role in photoreception. As a matter of fact, they may represent an element of the transduction chain that integrates gravi- and photo-signals.



Magnetoreception


From all environmental cues to which plants, fungi and microbial organisms are subjected, the magnetic field and its interaction with living matter is least understood. Even though there is ample evidence that the weak geomagnetic field and strong magnetic fields affect the growth pattern, differention and in certain instances also the orientation of plants and fungi, systematic physiological analyses of these phenomena are lacking (Galland and Pazur 2005). We have begun to analyze the effect of the geomagnetic field on chlorophyll biosynthesis, gravitropism and phototropism. The experiments are devised largely on the theory of the “radical-pair mechanism”, which predicts that various radical pairs – such as for example the above mentioned flavosemiquinones – contribute to magnetoreception. Our preliminary results indicate that Phycomyces as well as Arabidopsis are able to respond to the geomagnetic field.


2. Werner Schmidt

Fast primary reactions associated with gravireception


To identify the primary reactions that are associated with graviperception we employed in-vivo rapid-scan spectroscopy. The requisite equipment was devised by Prof. Dr. Werner Schmidt and constructed by the electronic and fine mechanical machine shops of the Biology Department in Marburg (Schmidt 2004a,b,c). The spectrometers make either fast spectral scans or measure in the dual-wavelength mode in a time scale of 5 ms. We found that gravitropic stimulation of sporangiophores of Phycomyces elicits absorbance changes that indicate the reduction of a cytochrome.

Fig2agalland

Fig2bgalland

Figures 2a,b: Weightlessness during 11 seconds of upward and another 11 seconds of downward flight of the airbus A300 ZERO-G. Coastline of Northern Spain, Mediterranean Sea, 2003.


These absorbance changes are specific and prerequisite for graviperception, because they are lacking in mutants with defective graviperception. In parabola flights of the ESA (European Space Agency) and the DLR (Deutsches Zentrum für Luft- und Raumfahrt) we analyszed these absorbance changes under weightlessness (duration 22 seconds) and hypergravity (1.8 X g; duration 30 seconds).
Fig3agalland
Fig3bgalland

Figure 3a,b: The experience of weightlessness in the airbus A300 ZERO-G. 2003 over the Mediterranean Sea (upper photograph: Paul Galland; lower: Werner Schmidt).


In these experiments we were able to show that the absorbance changes occur instantaneously (latency smaller than 20 ms). The gravity-induced absorbance changes (GIACs) represent thus the fastest graviresponses that are presently known (Schmidt and Galland 2004).


3. Franz Grolig

Cytoskeletal mechanisms of organelle transport and positioning


In particular in large and/or polarized cells more or less extensive long range transport systems in form of dynamic cytoskeletal "tracks" (microfilaments (MFs) and microtubules (MTs)) permit effective translocation of cargo hooked on track-associated molecular motor proteins (myosins, kinesins, dyneins) fuelled by ATP. Beside being a means of convection, intracellular motility often accomplishes (re)distri-bution and positioning of cellular constituents (organelles) as governed by internal (cell cycle-related) or external stimuli. Positioning can be considered as the result of an ongoing redistribution process leading to a stochastic non-random position as e.g. in case of light-governed relocation of chloroplasts in cells exposed to fluctuating light conditions. Premitotic relocation of the nucleus, a process which determines the site of the division wall, is one of the most intriguing examples of precise positioning in plant cells (where both, cargo and it´s destination, are highly specified), involving the interaction of MT- and MF-based forces.

The mechanisms underlying the sequential changes (preprophase band, phragmosome, phragmoplast) of the higher plant MT- and MF-cytoskeleton accompanying cytokinesis are still largely obscure. Comparative studies of cytokinesis in related organisms provide a chance to discover the evolutionary sequence leading from a primitive precursor structure to the derived structures, and therefore may help to identify functionally significant elements in the advanced cytokinetic apparatus.

Both aspects of organelle movement - transport and positioning - are studied in members of the charophycean green algae (Spirogyra, Mougeotia, Chara), a group closely related to the ancestors leading to the higher plants, and in the zygomycete Phycomyces blakesleeanus.

Fig4galland

Figure 4: Three-dimensional arrangement of chloroplast bands in the peripheral cytoplasm of Spirogyra crassa (Micrograph by Silke Lehmann).


Fig5galland

Figure 5: In Spirogyra crassa microfilaments in cooperation with microtubules mediate the central - transversal as well as longitudinal - positionioning of the nucleus (indirect immunofluorescence of microtubules; Grolig 2004).


Currently, we are particularly interested in the contribution of MFs and MTs to the cytomechanics of central nuclear positioning and of (light-governed) chloroplast positioning in Spirogyra (Mougeotia) to the positioning of gravisusceptors and to the cytomechanics of gravisusception in the sporangiophore of Phycomyces.
Fig6galland

Figure 6: Actin cytoskeleton in the apex of a stage-1 sporangiophore (without sporangium) of Phycomyces blakesleeanus (Grolig et al. 2005).


Experimental approaches include advanced microscopy (video and confocal), image analysis, cell models of reduced complexity, cell fractionation and biochemistry, reconstitution of in vitro motility.

4. Rainer Schmid and Sylvia Busch


In all brown algae (Phaeophyta) that have been investigated so far photosynthesis depends on blue light. Blue light activates a mechanism that makes CO2 available for photosynthesis. In the past the research activities were directed at the analysis of this CO2-concentrating mechanism and its regulation by blue light. In addition we also investigated steps of the signal transduction chain including photoreception. The research paper by Pearson et al. (2004) on the role of blue and green light for gamete release in Silvetia compressa concludes the research activities of the former coworkers, PD Dr. Rainer Schmid and Dr. Sylvia Busch (1995 – 2003).


5. Vitaly Sineshchekov


Dr. Vitaly Sineshchekov (Lomonosov state University Moscow) was a research visitor during the fall of 2005. He investigated on the basis of in-vivo fluorescence spectroscopy the role of two different phytochrome A populations in etiolated maize coleoptiles. He was particularly interested in the influence of gravity and specific phosphatase inhibitors on the behaviour of these phytochrome species (Sineshchekov and Galland 2005).



Publications


Corrochano, L.M. and P. Galland (2005) Photomorphogenesis and gravitropism in fungi. In: The Mycota I, Growth, Differentiation and Sexuality (edited by U. Kües and R. Fischer), pp. 231-257. Springer-Verlag Berlin Heidelberg, in press.

Galland, P. (2004) Phototropism. In: Handbook of Organic Photochemistry and Photobiology. Photobiology (W. M. Horspool and F. Lenci, eds.). pp. 132-1 – 132-17. Uniscience Series, CRC Press, Boca Raton, Florida, USA.

Galland, P., H. Finger and Y. Wallacher (2004) Gravitropism in Phycomyces: threshold determination on a clinostat centrifuge. J. Plant Physiol. 161, 733-739.

Grolig, F. (2004) Organelle movements: transport and positioning. In Hussey, P.J. (ed.) The plant cytoskeleton in cell differentiation and development, Annual Plant Reviews, Vol. 10, pp. 148-175, Blackwell Publishing, Oxford, CRC Press, Boca Raton

Grolig, F., H. Herkenrath, T. Pumm and P. Galland (2004) Gravity susception by buoyancy: floating lipid globules in sporangiophores of Phycomyces. Planta 218, 658-667.

Grolig, F., J. Moch, A. Schneider and P. Galland (2005) Actin cytoskeleton and organelle movements in the stage-1 sporangiophore of Phycomyces blakesleeanus: implications for growth and tropism. Planta, submitted. Grolig, F., M. Döring and P. Galland (2005) Graviperception by buoyancy: a mechanism ubiquitous among fungi? Protoplasma, in press.

Kosegarten, H., B. Hoffmann, E. Rroco, F. Grolig, K.-H. Glüsenkamp and K. Mengel (2004) Apoplastic pH and FeIII reduction in young sunflower (Helianthus annuus) roots. Physiol. Plant. 122, 95-106.

Pearson, G.A., E.A. Serrão, M. Dring and R. Schmid (2004) Blue- and green-light signals for gamete release in the brown alga, Silvetia compressa. Oecologia 138, 193-201.

Schmidt, W. (2004a) A high performance micro-dual-wavelength spectrophotometer (MDWS). J. Biochem. Biophys. Methods 58, 15-24.

Schmidt, W. (2004b) A mini-rapid-scan-spectrophotometer. J. Biochem. Biophys. Methods 58, 125-137.

Schmidt, W. (2004c) Quickly changing acceleration forces (QCAFs): vibration analysis on the A300 ZERO-G. Microgravity Sci. Technol. 15, 42-48.

Schmidt, W. and P. Galland (2004) Optospectroscopic detection of primary responses associated with the graviperception of Phycomyces: effects of micro- and hypergravity. Plant Physiol. 135, 183-92.

Sineshchekov, V.A. and P. Galland (2005) PhyA’/phyA’’ equilibrium in etiolated maize seedlings is connected with the activities of PP1 and/or PP2A phosphatases. Photochem. Photobiol. Submitted.

Tsolakis, G., N.K. Moschonas, P. Galland and K. Kotzabasis (2004) Involvement of G proteins in the mycelial photoresponses of Phycomyces. Photochem. Photobiol. 79, 360-70

Galland, P. and A. Pazur (2005) Magnetoreception in plants. J. Plant Res. 118, 371–389.


Doctoral theses


Fries, Volker (2004) Oktaedrische vakuoläre Proteinkristalle in Phycomyces blakesleeanus: Biochemische und fluoreszenzspektroskopische Charakterisierung


State examination theses


Gleim, Tatjana (2004) Gravitropismus in Phycomyces blakesleeanus.

Hörwick, Lisa (2004) Magnetoperzeption in Pflanzen und Pilzen.


Research grants


Galland: Grant of the DLR/BMBF: Investigation of rapid gravitropic primary reactions of fungi and higher plants in response to different accelerations - 50WB0146. 2004-2007.

Galland and V.A. Sineshchekov (Lomonosov State University Moscow): Binational grant of the DFG (436 RUS 17/99/04): Physiological role of the two native phyA populations in the light-induced modulation of photo- and gravitropisms in plants. Oct. – Dec. 2005.


Members of the group


Debelius, Agnes, technician
Fries, Volker, Ph.D. student (2000-04)
Gleim, Tatjana, student 2004
Göttig, Marco, technician
Grolig, Dr. Franz, senior scientist
Hörwick, Lisa, student 2004
Schmidt, Prof. Dr. Werner, senior scientist (coinvestigator of the DLR-/BMBF projects)
Schuchart, Dr. Hartwig, senior scientist
Seger, Norman, Ph.D. student
Sineshchekov, Dr. Vitaly, visiting senior scientist 2005
Völk, Sigrid, technician


Address


AG Prof. Dr. Paul Galland
Karl-von-Frisch-Str. 8
35032 Marburg

Zuletzt aktualisiert: 04.05.2006 · dohle

 
 
 
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