Abstract

Immune receptors constitute recognition sites to detect invading pathogens and to trigger defenses, and the abundance of these receptors at the plasma membrane depends upon the dynamic membrane trafficking network. Well-studied examples are the receptor kinases FLAGELLIN SENSING 2 (FLS2), EF-Tu RECEPTOR (EFR) from Arabidopsis and the Cf receptor-like proteins from tomato. To understand the mode of actions of these immune receptors, we investigate their spatio-temporal dynamics using advanced microscopy approaches upon ligand-induced activation. I will describe the internalization mechanism of FLS2 via a common, clathrin-mediated endosomal pathway of BAK1 -dependent receptor kinases, and I will discuss the role of kinase activity in this process. Focusing on late endosomal sorting, I will present results showing that FLS2 is a likely cargo of the ESCRT machinery and internalized inside multivesicular bodies for vacuolar degradation. These studies also suggest a role with regards to stomatal immunity and I will briefly describe our high-throughput imaging platform to investigate stomatal responses. To further study receptor-mediated endocytosis in plant immunity we investigated the spatio-temporal dynamics of tomato Cf-4, and I will describe recent results of its subcellular localization patterns. Taken together, advanced confocal imaging combined with functional studies allows us to tackle the dynamic changes involved in the interaction between plants and microbes at the cell surface.