Oligogalacturonides (OGs) – triggered Immunity in Arabidopsis thaliana

Plants, unlike mammals, lack mobile defender cells and a somatic adaptive immune system, instead relying on the innate immunity of each cell and on systemic signals emanating from infection sites. Pattern recognition receptors (PRRs) located on plasma membranes detect specific microbial molecular components called Microbe-Associated-Molecular Patterns (MAMPs) or self-derived molecules released upon cell damage, known as Damage-Associated-Molecular-Patterns (DAMPs). Patter-Triggered-Immunity (PTI) is the first layer of plant immunity and involves several responses including Ca2+ influx, oxidative burst, defense gene expression, and phytohormone signaling. Oligogalacturonides (OGs) are cell-wall DAMPs composed of alpha-1,4-linked galacturonosyl residues formed by the action of microbial polygalacturonases (PGs) and their plant inhibitors (PGIPs). Transgenic Arabidopsis plants expressing a PGIP-PG chimera named “OG-machine” under inducible promoters release OGs on command that confer resistance to many microbes. However, over-accumulation of OGs in these plants also results in growth penalties and may culminate in a deleterious hyper-immunity including cell death. This research aims to elucidate the metabolic and molecular pathways involved in OG-triggered immunity.