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Technical University of Munich

Research interests Dr. Philipp Denninger

Cell polarity and signalling in plants

During the development of multicellular organisms, cellular growth and differentiation need to be coordinated and tightly regulated, which may require asymmetric cell divisions and polar growth. The polar distribution of proteins and their enrichment in membrane domains within a cell underlies these mechanisms. In plants, key regulators of this cell polarity are the RHO OF PLANTS (ROP) RhoGTPases, which are activated by GUANINE NUCLEOTIDE EXCHANGE FACTORS (ROPGEFs). The Denninger group studies these proteins to understand how they polarize and how they activate polar growth. 

To address this, we use pollen tube growth, cell division, and other cell polarization events in Arabidopsis thaliana, Marchantia polymorpha and Zea maize as model systems. With these results we aim to identify the general mechanisms that initiate and regulate cell polarity, which are responsible for cellular growth and general plant development.

Previous results

  • We identified a novel ROPGEF required for root hair initiation and discovered that individual ROPGEFs have distinct functions within one cell (Denninger et al., 2009).
  • We identified which ROPGEFs drive pollen germination and described that polar membrane domains can flexibly shift within the cell (Bouatta et al., 2024).

Research goals

  • We want to understand how cell polarity domains are initially selected and established. We investigate this during pollen germination and in dividing root cells, to study how these cells can for a novel polarity domain that leads to reorientation of cellular growth.
  • We want to identify the spatiotemporal composition of ROP signalling complexes during polar growth. We use different in vivo (e. g. Microscopy) and in vitro (e.g. Proteomics) techniques to study the pollen ROP signalling complex, which will allow us to understand which proteins are required for polar growth. 
  • We want to understand how premature polar growth and signalling can be restrained. We use different cellular systems (e. g. pollen tubes, root hairs, papilla cells) to investigate how cellular signalling pathways are negatively regulated, which is required for normal plant development, as uncontrolled cellular signalling and growth is prevented.

Main methods

  • Confocal microscopy
  • Image analysis and quantification
  • Quantitative protein-protein interaction studies (MST, FRET) 
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