Isabel Jungkunz


C2 Functional analysis of the interaction between host chaperones and viral transport proteins

Principal investigator
Uwe Sonnewald

Yves Muller

PhD exam: 18.04.2011

Role of molecular chaperones for virus spread in infected Arabidopsis thaliana plants

Molecular chaperones of the DnaK/DnaJ family (also called HSP40/HSP70) are essential host factors of viral replication in host cells. In humans, they are supposed to be involved in assembly and disassembly of viruses but can additionally initiate the ubiquitin-mediated degradation of some target proteins and hence may be involved in host defence. In case of phytopathogenic viruses only circumstantial evidence for the involvement of chaperones in replication and spreading exists. In our preparatory work we were able to demonstrate for the first time that a specific member of the DnaJ-protein family, NtCPIP1, interacts with the viral coat protein of the potato virus Y (PVY-CP) and that this protein is essential for potyvirus infection of host plants. Over-expression of J-domain deficient variants of PVY-CP interacting DnaJ-like proteins strongly increased virus resistance of transgenic tobacco plants indicating a crucial role of functional DnaJ-proteins during PVY infection. The negative effect of impaired chaperone function on viral pathogenicity seemed to be the consequence of strongly delayed cell-to-cell movement, as visualized by particle bombardment of transgenic plants with GFP-tagged PVY. Therefore, we propose that DnaJ-like proteins act as important susceptibility factors during PVY infection, possibly by recruiting heat shock protein 70 (HSP70) chaperones for viral assembly and/or cellular spread. Based on this preparatory work we would like to understand the molecular processes in more detail. Therefore, we propose to search for interacting HSP70 and additional co-chaperones involved in potyvirus infection and to characterize their mode of action.

Figure: The CLSM pictures show a GFP-AtHsp70-1-fusion expressed in stable transformed Nicotiana tabacum plants after incubation of leave discs for 2 or 3 hours at 43°C or room temperature. After heat treatment besides of the cytosolic and nuclear localization aggregates like stress granules appear (scale bar =10 µm).



Vogel, F., Hofius, D., Paulus, K. E., Jungkunz, I. and Sonnewald, U. (2010). The second face of a known player: Arabidopsis silencing suppressor AtXRN4 acts organ-specifically. New Phytol 189, 484-493.

Jungkunz, I., Link, K., Vogel, F., Voll, L. M., Sonnewald, S. and Sonnewald, U. (2011). AtHsp70-15-deficient Arabidopsis plants are characterized by reduced growth, a constitutive cytosolic protein response and enhanced resistance to TuMV. Plant J 66, doi: 10.1111/j.1365-313X.2011.04558.x.

Hofius, D., Maier, A., Dietrich, C., Jungkunz, I., Börnke, F., Maiss, E. and Sonnewald, U. (2007). Capsid protein-mediated recruitment of host DnaJ-like proteins is required for Potato virus Y infection in tobacco plants. J Virology 81, 11870-11880.



September 2010 2nd Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
AtHsp70-15 deficient Arabidopsis plants are characterized by reduced growth, a constitutive cytosolic protein response and enhanced resistance to TuMV”
September 2009 First Annual Retreat, Erlangen School of Molecular Communication, Schloss Atzelsberg, Atzelsberg, Germany
Silencing of the proposed nucleotide exchange factor AtHsp70-14/15 results in impaired plant growth and enhanced virus tolerance”
February 2009 22. Tagung Molekularbiologie der Pflanzen, Dabringhausen, Germany
„Charakterisierung der cytosolischen Hsp70-Isoformen in Arabidopsis thaliana“
September 2009 Botanikertagung 2009 – Plants for the future, Leipzig, Germany
„AtHsp70-14/15 silenced Arabidopsis plants are characterized by impaired stomata closure and reduced plant size”