Cell walls and their role in the plant root microbiome

Plant roots form a microbiome that interacts at the cell wall extracellular matrix before entering the cell. The root primary and accessory walls present a dynamic, cell-type-dependent scaffold that microbes must navigate, using shared cellulose or contrasting chitin motifs and influencing plant gene responses that encode enzymes for cell wall biosynthesis and degradation. We propose that an interface evolves as microbes reach the root tip and interact with host polymers, potentially driving concurrent degradation of root and microbial cells. Knowledge gaps span diffusion, fluid flow, nutrient exchange, and the physics of microbial motion within the wall boundary. Advances in in situ imaging and mathematical modelling can help understand the dynamics of cell walls to design root microbiomes to function in agroecosystems.