Cell wall bricks of defence: the case study of oligogalacturonides

Abstract

The plant cell wall (CW) is more than a structural barrier; it serves as the first line of defence against pathogens and environmental stresses. During pathogen attacks or physical damage, fragments of the CW, known as CW-derived Damage-Associated Molecular Patterns (CW-DAMPs), are released. These molecular signals play a critical role in activating the plant's immune responses. Among CW-DAMPs, oligogalacturonides (OGs), fragments derived from the breakdown of pectin, are some of the most well-studied. This review highlights recent advances in understanding the functional and signalling roles of OGs, beginning with their formation through enzymatic CW degradation during pathogen invasion or mechanical injury. We discuss how OGs perception triggers intracellular signalling pathways that enhance plant defence and regulate interactions with microbes. Given that excessive OG levels can negatively impact growth and development, we also examine the regulatory mechanisms plants use to fine-tune their responses, avoiding immune overactivation or hyper- immunity. As natural immune modulators, OGs (and more generally CW-DAMPs), offer a promising, sustainable alternative to chemical pesticides by enhancing crop resilience without harming the environment. By strengthening plant defences and supporting eco-friendly agricultural practices, OGs hold great potential for advancing resilient and sustainable farming systems.

Keywords: DAMP (damage associated molecular pattern); biotic stress; cell wall; crop protection; eco-friendly agriculture; oligogalacturonides (OGs) plant-microbe interactions; plant immunity elicitor; sustainable agriculture.

Figure 1

Plant cell wall structure and oligogalacturonides (OGs) signalling pathway. The illustration represents the plant cell wall and the release of DAMPs, such as OGs, upon CW rupture. The inset illustrates OG biosynthesis: homogalacturonan is cleaved by PG, whose action is modulated by PGIP to produce and accumulate OGs with a DP of 10–15. OGs are recognised by Pattern Recognition Receptors (PRRs) on the cell surface, triggering signalling cascades that involve Reactive Oxygen Species (ROS) production, activation of Mitogen-Activated Protein Kinase (MAPK) pathways, transcriptional reprogramming and hormone production and accumulation. Together, these responses collectively enhance plant resistance to pathogens.

Figure 2

Benefits of oligogalacturonides use for sustainable agriculture. OGs are valuable molecules in agriculture due to their sustainability in production, minimal environmental impact, and beneficial effects on plants. OG-based products could be produced starting from the degradation of plant-based matrices that are rich in polysaccharides through different processes, such as microbial digestion, enzymatic hydrolysis, or safe chemical treatment. The incorporation of agricultural waste within a circular economy framework not only promotes sustainability but also reduces environmental impact and production costs. The application of OG-based products not only induces plant resistance against biotic and abiotic stress but also improves plant yield and fitness, affecting different processes as reported in the right circle (created in BioRender).