Probable histone demethylase that promotes flowering independently of the photoperiod and vernalization pathways by repressing FLOWERING LOCUS C (FLC), a floral repressor that blocks the transition from vegetative to reproductive development. Probably mediates histone H3 'Lys-4' demethylation at FLC locus. Seems to act in partial redundancy with LDL1 and LDL2 to repress FLC expression. Required for histone H4 deacetylation of FLC locus. May be a component of the histone deacetylase complex. Forms a histone deacetylase complex with HDA5, HDA6 and MSI4/FVE that represses FLC gene expression to control flowering time (PubMed:21398257, PubMed:25922987). Required for systemic acquired resistance (SAR) toward pathogenic bacteria (e.g. Pseudomonas syringae pv tomato DC3000 (avrPto)) (PubMed:32392578). Together with FLD and MSI4/FVE, contributes to dehydroabietinal-dependent (DA, a diterpenoid tricyclic diterpene) activation of flowering ans SAR (PubMed:32392578). Interacts with HDA6. Induced by dehydroabietinal-dependent (DA), a diterpenoid tricyclic diterpene that promotes flowering and systemic acquired resistance (SAR). Sumoylated at Lys-287, Lys-693 and Lys-770 by SIZ1. Sumoylation alters its activity and the histone H4 acetylation status of FLC locus, promoting FLC expression. Delayed flowering (PubMed:32392578). Impaired systemic acquired resistance (SAR) toward pathogenic bacteria (e.g. Pseudomonas syringae pv tomato DC3000 (avrPto)) (PubMed:32392578). Lost ability of dehydroabietinal-dependent (DA, a diterpenoid tricyclic diterpene) to trigger flowering and systemic acquired resistance (SAR) (PubMed:32392578). Belongs to the flavin monoamine oxidase family. Extended N-terminus.