Plant Cell Wall Remodelling in the Rhizobium–Legume Symbiosis

∗Corresponding author. E-mail: [email protected] Abbreviations: AGP, Arabinogalactan protein; GPI-anchor, Glycosylphosphatidylinositol lipid anchor; HRGP, Hydroxyproline-rich glycoprotein; IT, Infection thread; NF, Nod-factor (Lipochitin oligosaccharide); LPS, lipolysaccharide; PRP, proline-rich protein; UDP, uridine diphosphate Colonization of host cells by rhizobium bacteria involves the progressive remodelling of the plant–microbial interface. Following induction of nodulation genes by legume-derived flavonoid signals, rhizobium secretes Nod-factors (lipochitin oligosaccharides) that cause root hair deformations by perturbing the growth of the plant cell wall. The infection thread arises as a tubular ingrowth bounded by plant cell wall. This serves as a conduit for colonizing bacterial cells that grow and divide in its lumen. The transcellular orientation of thread growth is controlled by the cytoskeleton and is coupled to cell cycle reactivation and cell division processes. In response to rhizobium infection, host cells