Seminarkalender

September 2016
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Seminare

Seminare

Das Max-Planck-Institut für Molekulare Pflanzenphysiologie hat regelmäßig herausragende Forscher zu Gast, die Vorträge über ihre aktuellen Projekte halten und so den Austausch unter den Wissenschaftlern fördern.

Eine Übersicht über die kommenden Veranstaltungen finden Sie hier. Seminare finden für gewöhnlich Mittwochs in der Zeit von 14:00 Uhr bis 15:30 Uhr im Seminarraum im Zentralgebäude (1.052 und 1.053) statt, Abweichungen in Zeit und Ort sind jedoch möglich.

October 2016

Dave Savage - Fixed: Systems and synthetic biological approaches for understanding photosynthetic CO2 fixation

Cells usestructure to catalyze and facilitate the chemical reactions of metabolism. Thisprinciple is exemplified by the process of carbon dioxide assimilation inphotosynthetic cyanobacteria, which coordinate myriad biochemical components inspace and time, in order to achieve a single physiological goal – convert solarpower into fixed chemical energy. An essential player in this process is thecarboxysome, a protein-based organelle composed of an icosahedral proteinshell, which encapsulates the enzymes RuBisCO and carbon anhydrase within a~100 nm structure. Despite knowledge of the overall structure of thecarboxysome, much less is known about the molecular interactions driving itsself-assembly and how this process is capable of occurring in the complex invivo environment. Here, I describe our biochemical efforts to elucidate amechanistic picture of how the carboxysome assembles and functions in the cell.At the same time, our lab is also interested in developing a holistic pictureof how a coordinated physiology emerges from the many different proteinactivities, including the carboxysome and numerous transporters, found incyanobacteria. To this end, I present our recent efforts at reconciling theseactivities using a mathematical reaction-diffusion model of carbon dioxideassimilation. Finally, a general challenge to studying physiology is the lowthroughput of assays for quantifying metabolism. I therefore conclude with ourefforts at using protein engineering for constructing fluorescent metabolitebiosensors and enabling high-throughput studies of metabolism.  [mehr]

Patricia Leon-Mejia - Chloroplastsignals that impact leaf development

Chloroplast signals that impactleaf developmentThe most conspicuousfunction of chloroplasts is photosynthesis. However, these organelles alsofunction as factories that synthesized a pletora of essential compounds forplant life. Chloroplasts are thus central an enviromental sensor of the cell,and this information is transmitted to the ncucleus through retrogradesignaling, modulating the expression of nuclear-genes to fine-tune the generalplant developmental and external responses. Recent advances have demonstratedthe existence of multiple retrograde signaling pathways, but only few signalsresponsible for this regulation have been identified.  In recent years,evidence has supported that apocarotenoids are important signals that regulatediverse aspects of plant and animal development. The characterization of an Arabidopsisclb5 mutant, impaired in early chloroplast development, provided geneticand molecular evidences that the accumulation of apocarotenoid profoundlyaffects nuclear and plastid gene expression as well as leaf development. Thealbino clb5 mutant of Arabidopsis displays a unique defect in themorphology of the leaf with radial shape and defects in leaf polarity, that isnot observed in other albino mutants supporting the idea that chloroplaststatus is tightly monitored and strongly correlated with leaf development.These phenotypes are a consequence of the defect in the zeta carotenedesaturase (ZDS) activity that results in the accumulation of phytofluene andz-carotenoid intermediates. Our work also demonstrates that the signal responsiblefor the clb5 phenotypes is produced through specific cleavage ofphytofluene or z-carotenoids by the CCD4 enzyme. Furthermore, theanalysis of gene expression for ZDS and CCD4 shows an correlation acrossmultiple tissues and developmental stages. Using wide genome analysis, we havefound that this signal affects the expression of key nuclear-encoded genesimportant for leaf and plastid development as well as genes from thechloroplast genome in comparison to the carotenoid-deficient pds3 mutantplant, supporting the unique role that these carotenoids have over plantdevelopment. Finally, we found that the regulation on gene expression dependson specific cis-acting sequences located in the promoter region of thetarget genes. [mehr]

Christopher Grefen - Genetic analysis of GET pathway components in Arabidopsis thaliana

SNARE proteins catalyse the final step inmembrane fusion with their cognate SNARE partners through tight interaction viatheir cytosolic N-terminal domains. Their C-terminal membrane anchor pulls theopposite membranes together, overcoming the strong dehydration forces associatedwith the lipid bilayer and ultimately leading to fusion of the two membranes.This important function is prerequisite to a multitude of vital cellularfunctions such as trafficking of cargo to the outside of the cell or addingadditional membrane material to the plasma membrane for expansion.In yeast and mammals integration oftail-anchored (TA) membrane proteins seems to be facilitated via cytosoliccomponents in an ATP-dependent fashion. This ‘Guided-Entry of TA proteins’(GET) pathway has not been described in plants where research focusses on theimport pathways into chloroplasts and mitochondria. How the abundance of SNAREand other important TA proteins are integrated into the ER membrane in plantsis currently entirely unknown.We have identified the candidates involved in aputative GET pathway of Arabidopsis.Our data show that plants have evolved multiple orthologues of specific GETpathway components, albeit in a compartment-specific manner. In contrast,others seem to be absent in plants suggesting differences in the proteininsertion mechanism or the development of alternative pathways. The latterhypothesis is supported by highly specific rather than general phenotypesassociated with loss-of-function lines highlighting the plant’s need for backupinsertion mechanisms. [mehr]

November 2016

Jane Mellor

[mehr]

Łucja Kowalewska

[mehr]

Magalie Uyttewaal

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Jenny Russinova

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January 2017

Steve Penfield

[mehr]

Marja Timmermans

[mehr]

March 2017

Keiko Sugimoto

[mehr]

 
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