Apoplast manipulation

Apoplast manipulation by plant pathogens

We investigate the manipulation of extracellular plant proteins by pathogens. The apoplast (the extracellular space in plants) is one of the largest biotic interfaces on earth, colonized by microbes (bacteria, fungi and oomycetes). This dynamic environment with changing temperatures, humidity and light is also controlled by the host plant, which responds to microbes by secreting defence compounds and proteins. Defence proteins include a broad range of hydrolytic enzymes such as glycosidases, proteases and lipases that are potentially harmful for microbes colonizing the apoplast. We study how successful pathogens manipulate these defence proteins to suppress their activity. The aim of our research program is to identify manipulated enzyme activities and unravel their molecular mechanism and biological relevance. Our central model system is the interaction between wild tobacco (Nicotiana benthamiana) and three pathogenic strains of the bacterium Pseudomonas syringae. Some studies are extended to include infection of other solanaceae plants by the leaf mould fungus Cladosporium fulvum and the potato late blight pathogen Phytophthora infestans, and infection of wheat by the fungal pathogen Zymoseptoria tritici. Our studies on the tomato proteases and its inhibition by Avr2 from Cladosporium fulvum and EpiCs from Phytophthora infestans has revealed how important these host enzymes are in basal defence, and how the arms-race during co-evolution has shaped natural variation in host proteases.