The Vacuolar H⁺-ATPase subunit C is involved in oligogalacturonide (OG) internalization and OG-triggered immunity

In plants, the perception of cell wall fragments initiates signal transduction cascades that activate the immune response. Previous research on early protein dynamics induced by oligogalacturonides (OGs), pectin fragments acting as damage-associated molecular patterns (DAMPs), revealed significant phosphorylation changes in several proteins. Among them, the subunit C of the vacuolar H⁺-ATPase, known as DE-ETIOLATED 3 (DET3), was selected to elucidate its role in the OG-triggered immune response. The Arabidopsis det3 knockdown mutant exhibited defects in H₂O₂ accumulation, mitogen-activated protein kinases (MAPKs) activation, and induction of defense marker genes in response to OG treatment. Interestingly, the det3 mutant showed a higher basal resistance to the fungal pathogen Botrytis cinerea that, in turn, was completely reversed by the pre-treatment with OGs. Our results suggest a compromised ability of the det3 mutant to maintain a primed state over time, leading to a weaker defense response when the plant is later exposed to the fungal pathogen. Using fluorescently labelled OGs, we demonstrated that endocytosis of OGs was less efficient in the det3 mutant, implicating DET3 in the internalization process of OGs. This impairment aligns with the observed defect in the priming response in the det3 mutant, underscoring that proper internalization and signaling of OGs are crucial for initiating and maintaining a primed state in plant defense responses.