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P 19 - Prof. Dr. Klaus Palme

Functional specificity of protein interaction networks in plant hormone dependent regulation of cell fate determination




Prof. Dr. Klaus Palme

Institut für Biologie II/Botanik

Schänzlestr. 1

79104 Freiburg

Phone: +49 761 203-2707/2954

Fax: +49 761 203-2899



Project Summary


Multicellular life depends on the functional compartmentalization of cells through co-ordinated differentiation. In plants, several of the processes, which specify cell fate, are driven by transport of the growth regulator auxin. Auxin forms instructive concentration gradients and is transported both within and between cells by members of the PIN protein family. PIN proteins regulate both the cytosolic concentration of auxin and its access to nuclear receptors. In the current funding period, we have biochemically characterized the protein environment of PIN1, its functional specificity and mechanisms which regulate its activity. Now we plan to investigate how, when, where and to what extent spatially and temporally-defined PIN regulation modules (phosphorylation, localized inhibitor production, regulation of protein stability and cytoskeleton structure) connect to control cell differentiation. In the planned work program, we will exploit novel techniques which have been developed within the project over the last funding period. These include the use of iRoCS, an integrated root co-ordinate system, which automatically recognizes cell boundaries and normalizes their co-ordinates, allowing rigorous statistical analysis of root structure at cellular resolution to assess functional specificity of protein complexes at cellular resolution. We will perform a mechanistic examination of the structural basis for PIN1 inhibition by phytotropins and evaluate the spatial distribution of active and inhibitor-bound PIN1. We will further functionally analyze PIN1 interacting proteins through the general and tissue-specific manipulation of PIN1 complex structure with respect to location and transport dynamics, complex reconstitution and functional analysis in single cells. We also plan  to analyze the composition of endoplasmic reticulum-localized PIN5, 6 and 8 protein environments and comparatively investigate the factors which define subcellular PIN localization. Finally we plan to analyze the trafficking and turnover of PIN1 by endocytosis, quality control, and subsequent direction either back to the membrane, or to degradation pathways, and the consequences for cell fate and development. In this way, we will follow the functional specificity of PIN interacting proteins and determine in which contexts and how their functional specificity affects PIN protein localization and function.

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