Adriana Montes

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C7 Modulation of cellular processes and Rac/Rop (Rho) activity in Arabidopsis by Pto TTSS effector proteins

Principal investigator
Benedikt Kost

Mentor
Andreas Burkovski

Modulation of cellular processes and Rac/Rop (Rho) activity in Arabidopsis by Pto TTSS effector proteins

The virulence of Pseudomonas syringae is dependent on complex repertoires of effector proteins injected into host cells cytoplasm by type III secretion systems (TTSS). These effector proteins interfere with the double layered plant immune system composed of pathogen-associated molecular pattern-triggered immunity (PTI) and effector-triggered immunity (ETI), shutting down defense reactions and allowing the pathogen to successfully grow and multiply within infected tissues. Most of these effectors appear to have overlapping functions, making it difficult to characterize their individual mode of action. As a result, the cellular functions of most pathogen effectors are not well understood to date.

Rac/RopGTPases, plant homologs of Rho family small GTPases, are increasingly recognized as important general regulators of plant growth and development, which are also required for plant stress responses. Rho GTPase are active as signaling molecules in the GTP bound form, in which they interact with multiple downstream effectors to stimulate signaling cascades that regulates and coordinating different cellular processes. GTP hydrolysis by intrinsic GTPase activity converts Rho GTPases to the GDP bound inactive form. Conserved families of regulatory proteins directly interact with Rho GTPases to regulate their activity. GTPase activating proteins (GAPs) inactivate Rho signaling functions by increasing their low intrinsic GTPase activity. By contrast, guanine nucleotide exchange factors (GEFs) activate these functions by promoting the exchange of GDP for GTP. Guanine nucleotide dissociation inhibitors (GDIs) modulate Rho signaling by transferring inactive, GDP bound Rho GTPase from the plasma membrane to the cytoplasm. The functions of Rac/RopGTPases are best understood in plants cells that undergo directional expansion. Rac/Rop signaling controls the polar growth of these cells by regulating and coordinating cellular processes including Ca2+ influx into the cytoplasm, NADPH oxidase dependent ROS production, actin reorganization and membrane trafficking. ´These cellular processes are also essential for PTI and ETI based plant defense responses. Rac/RopGTPases therefore appear highly likely to play important roles also during plant pathogen interactions.

In mammalian system, it has been shown that TTSS effectors can directly target Rho GTPase activity by acting as GAPs or GEFs. Other TTSS effectors were shown to modulate the activity of host cell GEFs or to inactivate host cell Rho GTPases by proteolytically cleaving off their C-terminal membrane anchors and by thereby transferring them to the cytoplasm. Effectors of plant bacterial TTSS pathogens with similar functions remain to be identified.

This project has been designed to characterize functions of Pto TTSS effector proteins in the modulation of structures, processes and Rac/RopGTPase activity in infected Arabidopsis cells. It aims at enhancing our understanding of cellular and molecular processes underlying specific model plant pathogen interactions and focusses on the detailed cell biological characterization of these interactions.

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Publications

 

Presentations

July 2015 7th Annual Retreat, Erlangen School of Molecular Communication, Schloss Hirschberg, Beilngries, Germany
”Modulation of cellular processes & ROP (Rho) activity in Arabidopsis by P. syringae (Pto) TTSS effector proteins”
Talk
     
July 2014 6th Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
“Modulation of cellular processes & ROP (Rho) activity in Arabidopsis by P. syringae (Pto) TTSS effector proteins”
Talk
     
July 2013 5th Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
Modulation of cellular processes and Rac/Rop (Rho) activity in Arabidopsis by Pto TTSS effector proteins
Talk
     
April 2013 Cornell University, Ithaca, NY, USA
Modulation of cellular processes and ROP activity by P. syringeae type III effectors"
Talk
     
March 2013 First ECROPS Retreat, Beilngries-Leising, Germany
Functional characterization of serine/threonine kinase, Rac5 associated kinase 1 (RAK1)"
Poster
     
2010 Presentation at the LSM-User Meeting
Mechanism and Regulation of Polar Cell"
Talk
     
2010 XXI International Congress on Sexual Plant Reproduction, Bristol, UK
Markers for F-actin: visualization of the cytoskeleton dynamics in Nicotiana tabacum pollen tubes"
Poster