Role of oligogalacturonides (OGs) and their oxidation by OGOX enzymes in systemic plant defence responses

Cell wall damage caused by wounding or pathogens releases Damage-Associated Molecular Patterns (DAMPs), including oligogalacturonides (OGs), which activate local immune responses via pattern recognition receptors (PRRs). OGs accumulate through the combined action of microbial polygalacturonases (PGs) and plant PG-inhibiting proteins (PGIPs). The activity of OGs is tightly regulated: OG oxidases (OGOXs), a class of Berberine Bridge Enzyme-like proteins, inactivate them to prevent excessive immune responses that could impair growth or trigger cell death. While OG-triggered local defenses are well described, their ability to induce systemic signals remains unclear. Long-distance signaling from local stress may involve calcium waves, ROS, hydraulic and electric signals, and is often associated with JA/JA-Ile accumulation and expression of wound-responsive genes. This study investigates the involvement of OGs in systemic defense by analyzing distal responses such as stomatal closure, systemic gene expression activation, and resistance to pathogen infection. Furthermore, we explore the role of OG oxidation by OGOXs in modulating these systemic effects, potentially acting as a negative feedback mechanism to fine-tune plant immunity without compromising growth.