Root cell types as an interface for biotic interactions

Root responses to environmental stresses show a high level of cell type and developmental stage specificity. Interactions with beneficial and pathogenic organisms – including microbes and parasites – elicit a set of transcriptional responses unique to each root cell type, often dependent on their differentiation state. Localized changes to the cell wall and to the integrity of root cell types can serve as a physical barrier for a range of pests. Conversely, certain microorganisms weaken existing barriers within root cell types. Interactions with microorganisms vary between roots of different developmental origins and cellular architectures. Here we provide an overview of the molecular, architectural, and structural properties of root cell types crucial to both maintaining beneficial interactions and protecting from pathogens. Individual root cell types perceive and respond to biotic factors in unique and distinct manners dependent on their developmental stage.Plants discriminate soil-borne pathogens from commensal microorganisms via spatially restricted immune responses and cell-type-specific transcriptome reprogramming.The integrity of root endodermal diffusion barriers influences root interactions with soil-borne microbes and vice versa.Root cortex cellular architecture impacts root interactions with fungi.The endodermis is a likely barrier for a broad range of pathogens across kingdoms.