Plant Immunity Mini-Workshop
Programme:
10:00: Professor Paul Birch, University of Dundee/James Hutton Institute, Dundee, United Kingdom
RXLR effectors follow an unconventional Rab7-linked secretion pathway associated with extracellular vesicle production
Phytophthora infestans, cause of potato late blight disease, delivers a suite of RXLR effectors into host plant cells to subvert immunity, whereas apoplastic effectors act extracellularly. Although the RXLR-EER motif in these effectors is critical for host translocation and is proteolytically cleaved prior to secretion, the relevance of this processing is not understood. Prior evidence suggests RXLR effectors utilize a distinct, unconventional secretion pathway, raising the question of whether the RXLR-EER motif influences selection of the secretion route. We combined genetic, molecular and cell biology approaches to investigate the RXLR effector secretion pathway. We reveal that RXLR effectors are translated into the ER prior to proteolytic processing and secretion. However, confocal microscopy revealed that RXLR and apoplastic effectors are trafficked by distinct, motile vesicular compartments within cultured hyphae. Fusing the Golgi recycling signal KDEL to RXLR effectors did not impair their secretion, in contrast to apoplastic effectors, which were recycled to the ER, indicating that RXLR effectors bypass the canonical ER-to-Golgi pathway. Secretion of RXLR effectors involved RAB7-associated vesicles but not vesicles carrying the Trans-Golgi Network-associated vacuolar sorting receptor BP80. Mutation of the RXLR-EER motif not only prevented effector translocation into host cells but also led to their secretion by the canonical ER-to-Golgi pathway. Importantly, RXLR effectors associate with extracellular vesicles (EVs), whereas RXLR-EER motif mutants show reduced EV association and are rerouted through the canonical ER-to-Golgi secretion pathway. These findings demonstrate that the RXLR-EER motif governs effector sorting into an unconventional, EV-linked secretion route. This study sheds light on the molecular basis of effector trafficking in P. infestans and underscores the potential role of EVs in delivering virulence factors during host colonization.
10:50: Professor Ulrich Schaffrath, RWTH Aachen University, Germany
Characterization of virulence factors potentially involved in host-specificity of Magnaporthe oryzae isolates
The blast fungus Magnaporthe oryzae is a threat to global food security causing high yield losses in rice and wheat production. Molecular analyses identified multiple divergent lineages and sub-divisions within the pathogen population, which are preferentially associated with a particular host genus. Comparative genomic analysis has been used to enquire for differences within the genomes of different isolates and this led to the identification of potential host-specific genes. However, there is a significant lack of experimental proof for their virulence and/ or molecular function.
To close this gap, we established a toolbox for in-depth characterization of such candidate genes. Actually, we investigate two gene candidates: i) a Nudix-hydrolase present in most Magnaporthe-isolates except those infecting wheat, and ii) another gene solely present in wheat-infecting isolates. Confocal laser-scanning microscopy confirmed that both genes are secreted and qPCR pointed to a precise regulation during the infection process. To determine a contribution to host specificity of M. oryzae, we utilized CRISPR/Cas9 mediated genome editing and generated mutants with gene deletion, complementation, in locus mRFP-tagging and overexpression. Impact of these genetic modifications on fungal virulence was observed for both genes.
All are welcome!
Time and place
17 March 2026, 10:00-12:00
Seminar room R322/R323 - entrance 4, 3rd floor
Thorvaldsensvej 40, 1871 Frederiksberg C