Transcytosis shuts the door for an unwanted guest.

Developmental Genetics, Center for Plant Molecular Biology, University of Tübingen, Auf der Morgenstelle 3, D-72076 Tübingen, Germany. Electronic address: .
Trends in Plant Science (Impact Factor: 13.48). 07/2013; DOI: 10.1016/j.tplants.2013.06.002
Source: PubMed

ABSTRACT Penetration resistance is a well-described plant defense process, in which SOLUBLE N-ETHYLMALEIMIDE-SENSITIVE-FACTOR ATTACHMENT RECEPTOR (SNARE) proteins have essential roles in membrane fusion processes. Strong focal accumulation of these proteins at the site of attack by powdery mildew fungi has been considered important for their function. However, recent insight indicates that transcytosis, leading to the formation of exosomes, has an important role in this defense and, furthermore, that strong accumulation of these SNARE proteins with the exosomes is biologically irrelevant. These findings alter the established function of SNAREs in penetration resistance; therefore, in this opinion, we propose that PEN1 and its SNARE partners function on an endosome in their control of penetration resistance.

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    ABSTRACT: Obligate biotrophs, such as the powdery mildew pathogens, deliver effectors to the host cell and obtain nutrients from the infection site. The interface between the plant host and the biotrophic pathogen thus represents a major battleground for plant-pathogen interactions. Increasing evidence shows that cellular trafficking plays an important role in plant immunity. Here, we report that Arabidopsis thaliana ENHANCED DISEASE RESISTANCE4 (EDR4) plays a negative role in resistance to powdery mildew and that the enhanced disease resistance in edr4 mutants requires salicylic acid signaling. EDR4 mainly localizes to the plasma membrane and endosomal compartments. Genetic analyses show that EDR4 and EDR1 function in the same genetic pathway. EDR1 and EDR4 accumulate at the penetration site of powdery mildew infection, and EDR4 physically interacts with EDR1, recruiting EDR1 to the fungal penetration site. In addition, EDR4 interacts with CLATHRIN HEAVY CHAIN2 (CHC2), and edr4 mutants show reduced endocytosis rates. Taken together, our data indicate that EDR4 associates with CHC2 and modulates plant immunity by regulating the relocation of EDR1 in Arabidopsis. © 2015 American Society of Plant Biologists. All rights reserved.