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.

Richard S. Smith - Quantifying morphogenesis with MorphoGraphX

Morphogenesis emerges from complex interactions between genetic and mechanical processes. Computer simulation models are becoming increasingly important to aid our understanding of the complexity involved, in an emerging field that is now being called Computational Morphodynamics. Key to this methodology is the combination of experimental work with dynamic, spatial simulation modeling. In order to analyze shape change in developing organs, it is essential to be able to quantify cell shape and gene expression changes at cellular resolution, over multiple time points. Ideally, a full 3D quantification of shape change and gene reporter expression over time is desired. Unfortunately, this is often technically challenging. In cases where the processes of interest occur on a surface layer of cells, 2D (i.e. max) projections can be used. However on highly curved organs and tissues, flat projections can introduce too much distortion to accurately record cell shape change. Here I will present a new image processing software called MorphoGraphX that bridges this gap by working directly with curved surface images extracted from 3D data. After recognizing the shape of a 3D sample, the surface is extracted and the signal is projected on the surface to form a curved “2.5D” image. I will demonstrate many of the tools we have developed to enable image processing on these 2.5D images, and how to use them to quantify 4D confocal time-lapse data sets. Finally, I will present our inroads towards developing an integrated simulation and imaging environment for Computational Morphodynamics. [mehr]

July 2016

Jerry Eichler - Sweet and Extreme: N-glycosylation in the Archaea

It is now clear that N-glycosylation, the covalent linkage of glycans to select asparagine residues of target proteins, is a post-translational modification that occurs across evolution. While understanding of the eukaryal and bacterial versions of this universal protein-processing event is relatively advanced, far less is known of N-glycosylation in Archaea. This, despite the fact that N-glycosylation is seemingly widespread in Archaea and that archaeal N-linked glycans present diversity in composition and structure not seen elsewhere. Relying on the halophilic archaea Haloferax volcanii, originally isolated from the Dead Sea, as a model system, work in our group has tried to fill this void. Accordingly, bioinformatics, genetic, mass spectrometry and biochemical approaches have been employed to delineate the pathways used for the assembly of two distinct glycans N-linked to target proteins in Hfx. volcanii. The same general strategy is now being used to better understand N-glycosylation pathways in other Archaea. As such, our studies on archaeal N-glycosylation not only expand understanding of a universal post-translational modification, they also provide novel insight into life at extremes. [mehr]

Freek T. Bakker - Herbarium plastomics and Pelargonium (Geraniaceae) as a system for studying organellar evolution

Second generation sequencing has caused major breakthroughs in the use of archival DNA, and in the use of herbarium specimens in particular. Whereas this enables testing of historical biological hypotheses, concerns remained about accuracy of herbarium sequence data and the possibility of post-mortem damage. Using a panel of angiosperm trees we compared fresh and historic samples of the same individuals and concluded that such damage is negligible, and that specimen age per se does not predict sequencing success. 2nd generation sequencing retrieves herbarium plastomes surprisingly well, which opens up possibilities for further taxonomic and time sampling. One such clades is Pelargonium (Geraniaceae) which is well-known for its horticultural importance as well as its elevated levels of (organellar) genomic evolution, or genome instability. Whereas some family members have lost Inverted Repeats alltogether, the hybrid P x hortorum is usually cited as having the largest Inverted Repeats known in angiosperms. However, to what extend this is a natural phenomenon or a ‘breeding artefact’ remains to be ascertained. In addition, it is in this Pelargonium clade that both bi-parental inheritance and cytonuclear incongruence occurs. In the context of increased taxonomic sampling of plastomes around the parent species of P x hortorum, be it from herbarium or fresh material, we hope to elucidate this and other questions further. [mehr]

Jan Traas - Flower development: from morphodynamics to morphomechanics

Flower development : from morphodynamics to morphomechanics The shoot apical meristem (SAM) continuously generates leaves, flowers, and branches in higher plants. In the past decades, many components of the gene regulatory networks in the SAM have been identified. However, little is known about the spatiotemporal coordination between gene expression patterns and growth at cellular resolution. This lack of understanding is mainly due to the lack of comprehensive quantification of organ wide cell properties over time with regards to the underlying molecular networks. We address this problem in early flower development of Arabidopsis thaliana using high resolution confocal time lapse imaging, combined with genetic and biophysical approaches. Hereby we are focusing on the cell wall, which plays a central role in the control of growth rates and growth directions. Recent relevant publications from our team : Ali O, Traas J* (2016) Force-Driven Polymerization and Turgor-Induced Wall Expansion. Trends Plant Sci. 2016 May;21(5):398-409. Theoretical analysis. Boudon F, Chopard J, Ali O, Gilles B, Hamant O, Boudaoud A, Traas J*, Godin* C. (2015) A computational framework for 3D mechanical modeling of plant morphogenesis with cellular resolution.PLoS Comput Biol. 2015 Jan 8;11(1):e1003950. Sassi M, Ali O, Boudon F, Cloarec G, Abad U, Cellier C, Chen X, Gilles B, Milani P, Friml J, Vernoux T, Godin C, Hamant O, Traas J. (2014) An auxin-mediated shift toward growth isotropy promotes organ formation at the shoot meristem in Arabidopsis . Curr Biol. 2014 Oct 6;24(19):2335-42 Vernoux T, Brunoud G, Farcot E, Morin V, Van den Daele H, Legrand J, Oliva M, Das P, Larrieu A, Wells D, Guédon Y, Armitage L, Picard F, Guyomarc'h S, Cellier C, Parry G, Koumproglou R, Doonan JH, Estelle M, Godin C, Kepinski S, Bennett M, De Veylder L, Traas J. (2012) The auxin signalling network translates dynamic input into robust patterning at the shoot apex. Mol Syst Biol. 2011 Jul 5;7:508. [mehr]

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