Traffic Control for Plant Immunity and Receptor Kinases

In our attempts to understand the full nature of the interactions that occur between a potential pathogen and its host, we are elucidating the transport processes that are engaged by the plant’s immune system. Our main research focus has been how transport processes regulate defence activation. Combining genetic, molecular and biochemical approaches with cell biology we have comprehensively dissected the subcellular transport pathways dependent upon microbial stimulation. Our studies have revealed that clathrin- and ESCRT-mediated endosomal trafficking is required for plant defence and is important for stomatal immunity. To identify mechanistic and functional elements of transport-regulated immunity, we focus on how the pattern recognition receptors (PRRs), the primary sensors of the plant’s immune system, are transported through the cell. PRRs are receptor kinases and receptor-like proteins that must be presented at the plasma membrane to recognize potentially infectious pathogens and trigger immunity. We found that PRRs representing different protein families are endocytosed in a ligand-induced and BAK1/SERK3 co-receptor dependent manner. Together with the finding that activated PRRs (FLS2, EFR, PEPR1) traffic via a common endosomal pathway, this suggests a role of endocytosis in the regulation of receptor abundance at the plasma membrane triggered by ligand perception. Furthermore, endocytosis of activated FLS2 is mediated by clathrin and involves sorting by the ESCRT machinery. This indicates a link between transport processes involved in defence and PRR trafficking. Understanding these mechanisms is providing novel insights into the regulation of plant immunity. This work is supported by the Gatsby Charitable Foundation and a grant by the European Research Council (ERC).