Michalea Böhm

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Z1 Central project: Analytics & Imaging

Principal investigator
Uwe Sonnewald

Mentor
Andreas Burkovski

Proteomic Investigation of the Role of Stint, a Stress Induced Phosphoprotein in Nicotiana tabacum in Pathogen Defense

Stint (Stress Induced Phosphoprotein in Nicotiana tabacum) - a Hop (Hsp90/Hsp70 organization protein) homologue - contains three tetratricopeptid repeat (TPR) domains, two aspartate-proline (DP) repeats and one nuclear localization signal (NLS) (figure 1, Hedtmann 2012) as in yeast Sti1 (Nicolet and Craig 1989) and human HOP (Honore et al. 1992). As the name “Hsp90/Hsp70 organization protein” implies, Hop plays an important role in the Hsp90 chaperone cycle by binding and directing Hsp70 to Hsp90 as a co-chaperone. Besides this well-known function in protein transport, folding and stability, Hsp90 plays also a role in plant immunity. Liu et al. (2003) reported an association of Hsp90 with the resistance protein N in tobacco being responsible for TMV resistance. Furthermore Chen et al. (2010) demonstrated that Hop and Hsp90 are required for efficient transport of OsCERK1 – a Pattern Recognition Receptor (PRR) – from the Endoplasmatic Reticulum (ER) to the plasma membrane (PM) in rice. They also found that two more PRRs (OsFLS2 and OsBAK1) interact with Hsp90 and Hop in the ER. Thus Hop is essential for Chitin triggered immunity but also for resistance to rice blast fungus. In addition rice blast fungus infected Hop-overexpressing plants show much smaller lesions then the wildtype while lesions of Hop-silenced plants being even bigger.

Comparable results were also observed in Nicotiana tabacum by silencing Stint. Plants are more susceptible to bacterial infections with Pseudomonas syringae pv. tabaci. Interestingly the silenced plants show no significant phenotypic lesions after Potatovirs Y (PVY) infection while they have still a likewise high viral titer.
In this project the role of Hop/Stint in response to infection will be investigated in a proteomic approach utilizing high resolution mass spectrometry. Proteomes and later on Phosphoproteomes of infected and non-infected Nicotiana tabacum SNN and RNAi-Stint-silenced plants will be compared in a time-resolved manner. With the intention to find on the one hand targets of Hop endogenously in plants and on the other hand virus induced targets our efforts will finally lead to a better understanding of the molecular background of virus tolerance in Hop silenced Nicotiana tabacum plants.

Figure: Schematic illustration of Hsp90 cycle based on Mayer & Breton (2015): Hsp90 Chaperone Cycle: binding of Hop (upper left corner) to the C-terminal MEEVD motif and middle domain (MD) of Hsp90 prevents N-terminal dimerization and ATP hydrolysis. Subsequently a client bound HSP70 interacts with its IEEVD motif with Hop, leading to its positioning between the two Hsp90 domains. Binding of further co-chaperones (not shown) induces Hsp90 closed conformation and furthermore dissociation of the Hop-Hsp70 complex (Mayer & Breton, 2015). (C, C-terminal domain; M, middle domain; N, N-terminal domain).

 

Publications

 

Presentations

October 2016 8th Annual Retreat, Erlangen School of Molecular Communication, Schloss Schney, Lichtenfels, Germany
“Proteomic Investigation of Hsp90/Hsp70 organization protein (Hop) from Nicotiana tabacum
Poster