Welcome to the research projects of Prof. Dr. Julia Kehr

Long-distance signalling through the phloem plays a crucial role in regulating growth and development, as well as responses to environmental stresses and pathogen attack in higher plants. We characterise specific mobile RNAs that can act as such systemic signals and RNA-binding proteins (RBPs) involved in their transport. Many of the RBPs forming ribonucleoprotein complexes (RNPs) are able to undergo phase separation to build biomolecular condensates. We study the dynamics and functions of such protein-RNA condensates in vitro and in vivo.

Projects currently running include:

Systemic signalling during environmental stress and infection

In order to identify signalling molecules in the long-distance transport systems, we expose plants to various stress conditions (e.g. nutrient deficiency, drought, pathogens) in order to find RNAs and proteins that are increasingly transported under these conditions and are thus possible information transmitters (Buhtz et al. 2010).

Mobile RNAs, proteins, and RNA-protein complexes

To identify phloem proteins, RNAs and protein-RNA complexes, we extract phloem sap samples and study them using mass spectrometry-based proteomics and high-throughput RNA sequencing (Giavalisco et al. 2006, Kehr Kragler 2018). Native RNA-protein complexes are isolated and separated by specialised electrophoresis techniques (Ostendorp et al. 2017).

Protein-RNA condensates

Macromolecules such as proteins and RNAs can form membrane-free compartments, so-called condensates or granules, in cells by phase separation. In plants, these condensates can have a decisive influence on development, signal transduction or adaptation to stress conditions. We apply different microscopy- and assay-based methods in vitro and in vivo to decipher the composition of such condensates and the mechanism of their formation (Ostendorp et al. 2022).

Extracellular RNAs in infections

Extracellular RNAs (exRNAs) can play a key role in the infection of plants by pathogens and therefore have a high potential for improving plant health. The DFG Research Unit 5116 aims to develop a mechanistic understanding of RNA-mediated cross-kingdom communication between plant hosts and their pathogens. We are investigating the extent to which extracellular RNA exchange between plant hosts and the vascular wilt pathogen Verticillium longisporum is involved in the infection process and how extracellular RNAs and RNA-RBP complexes can be exchanged between hosts and pathogens.

RNA binding proteins in infection

The most harmful plant viruses are RNA viruses. Like endogenous RNAs, these viruses can spread throughout the plant via the phloem long-distance transport stream. We are characterising RNA-binding proteins from the plant host and the virus mediating systemic translocation.