PBImmunity

Die Rolle und Dynamik der pflanzlichen processing bodies während bakterieller Infektion

01.10.2021 bis 30.09.2023

Understanding the molecular dialogue between plants and pathogens is vital for developing effective and sustainable control strategies against the plant diseases that currently threaten food security worldwide. To protect themselves from these pathogens, plant immunity is efficiently regulated at the transcriptional and post-transcriptional level. The compartmentalization of mRNA into translationally repressed aggregates called processing bodies (PBs) is a key post-transcriptional regulatory process involved in development and stress responses. Preliminary results from the host team have shown that the bacterial plant pathogen Pseudomonas syringae (Pst) induces the formation of PB upon infection in an effector-dependent manner and that PB-defective Arabidopsis plants are more tolerant to Pst. This suggests that PBs are negative regulators of plant immunity that can be targeted by the bacterial effectors. The proposed project aims precisely at studying the role of PBs as post-transcriptional regulators of plant immunity and the ability of Pst effectors to modulate them. For this a combination of genetic, biochemical, proteomic and cell biology approaches will be conducted to address: 1) the dynamics and roles of PBs, 2) the effector-mediated modulation of PB formation and 3) the interplay between PBs and autophagy, all in the context of a compatible plant-bacterium interaction. The proposed project is structured in three work packages corresponding to the three beforementioned objectives. In the first part, the dynamics, involvement in immunity and composition of the assembled PBs upon infection will be studied. The dynamics of PB formation will be determined by confocal microscopy; the involvement in immunity, by the characterization of defence responses and transcriptomic features of a PB-defective Arabidopsis mutant; and the protein and RNA composition of purified PBs, by mass spectrometry and RNA sequencing respectively. In the second part of the project, Pst effectors will be screened for their ability to singly modulate PB formation, co-localize with PB markers and physically interact with PB components. The mechanisms behind this modulation will be further studied in the case of HopM1, the first identified effector able to associate with PBs and modulate their assembly. In the third part of the project, the interplay between PB formation and autophagy will be explored based on the preliminary result that PBs interact and co-localize with the selective autophagy receptor NBR1. For this, different combination of transgenic plants expressing PB markers and NBR1 and the respective mutants will be generated and characterized to genetically determine the contribution of each process to each other. Altogether, the propose project constitutes an innovative and well-rounded strategy to characterize for the first time the role of PBs in a compatible plant-pathogen interaction and identify the potential interplay between PBs and autophagy.