Title: Effectors and membrane trafficking in plant-pathogen interactions

Presenter: Prof. Hans Thordal-Christensen

University: Department of Plant and Environmental Sciences, University of Copenhagen, Denmark

Time: 9:30-11:15, April 23, 2015

Venue: Room A102, Institute of Microbiology, Chinese Academy of Sciences

Abstract: In my laboratory, we have for many years tried to understand how barley powdery mildew and wheat stripe rust fungi attack plants and how plants resist these pathogens. Powdery mildew and rust fungi are obligate plant pathogens dependent of forming haustoria in the host cells.

Pathogens secrete effector proteins to the apoplast and to the host cell to prevent defence mechanisms from manifesting resistance. We have been involved in unraveling the effector repertoire of the barley powdery mildew fungus and found about 500 such proteins. We use host-induced gene silencing to evaluate the importance of individual effectors in virulence and yeast 2-hybrid to find target proteins in the plant. Examples will be presented as well as a synthetic biology strategy for general effector inactivation.

Secondly, we are interested in plant membrane trafficking processes and how they are involved in plant interactions with microbes. Plant-powdery mildew fungi interact in leaf epidermal cells, which are amenable for confocal microscopy. We have previously shown that the syntaxin, PEN1, and ARF-GTPase guanine nucleotide exchange factor, GNOM, function on the same pathway defending the cell against penetration and haustoria establishment. We found that secretion of exosomes is involved in this defence mechanism.

Pathogen haustoria are surrounded by plant-generated membranes. The nature of these extrahaustorial membranes (EHM) remains enigmatic. We have addressed this question and found that the powdery mildew-associated EHM in barley cells shares features with the endoplasmic reticulum membrane (ER), although the EHM is not an extension of the ER.

These results brings us closer to designing disease resistant plants, using means independent of classically studied defence strategies.