2-oxoglutarate-dependent dioxygenase involved in the oxidation of jasmonate (JA), a stress-induced phytohormone synthesized in response to attack by pathogens and herbivores, which triggers the activation of defense responses via the JA-mediated signaling pathway. Converts JA to 12-hydroxyjasmonate (12OH-JA), an inactive form of JA. Is specific to free JA, and cannot oxidize the bioactive form jasmonoyl-L-isoleucine (JA-Ile) or other JA-amino acid conjugates. Prevents over-accumulation of JA and indirectly its bioactive form JA-Ile under stress response. Acts as a negative regulator of JA-mediated defense signaling, by contributing to 12OH-JA accumulation, which represses JA defense responses upon infection by the fungal pathogen Botrytis cinerea. Acts as a negative regulator of JA-mediated defense responses upon infestation by the herbivorous caterpillar Mamestra brassicae