Transcription repressor subunit of the SEU-LUG transcriptional corepressor of the C class floral homeotic gene AGAMOUS during the early stages of floral meristem development. Is part of the A class cadastral complex that define the boundaries between the A and C class homeotic genes expression and function. Interacts together with APETALA2 and SEUSS to repress AGAMOUS expression. Also plays a role in ovule and pollen development (PubMed:11782418, PubMed:15277686, PubMed:7743940). Implicated in embryo and floral development (PubMed:18390806). Involved in post-synthesis cell wall modifications necessary for mucilage extrusion from seeds upon imbibition, probably by promoting the expression of genes required for mucilage maturation (PubMed:21362134, PubMed:21402796). Involved in vegetative leaf morphogenesis at later stages of leaf development by restricting cell expansion during leaf growth (PubMed:15208345). Regulates the maintenance on leaf polarity and meristem activity as well as the initiation of embryonic shoot apical meristem (SAM) development (PubMed:19837869). Forms a corepressor complex with SEU; LUG is the transcription repressor subunit and SEU the specific DNA-binding adapter. Interacts with AGL24-AP1 and SVP-AP1 dimers, and possibly with SEP3, especially when complexed to SEU. Interacts with MED14, HDA19 and CDKE-1 (PubMed:15277686, PubMed:16679456, PubMed:17526732). Binds to YAB3, YAB5 and YAB1/FIL; these complexes promote adaxial cell identity in leaves as well as embryonic shoot apical meristem (SAM) initiation and postembryonic SAM maintenance (PubMed:19837869). A number of isoforms are produced. According to EST sequences. Expressed in young flower primordia, later becomes localized to petals, stamens and carpels. Is also expressed in vegetative tissues (PubMed:11058164). Expressed in roots, stems, leaves, seedlings, apex, flowers, flower organs and seeds (PubMed:18390806). Expressed prominently during both female and male gametes development (PubMed:11058164). Accumulates throughout young developing leaves, before being confined to the vasculature of older leaves (PubMed:19837869). Induced by exposures to biotic stress (e.g. Agrobacterium tumefaciens) and abiotic stress (e.g. hypoxia, cycloheximide, 2,4-dichlorophenoxyacetic acid, AgNO(3) and aminoethoxyvinylglycine). Repressed by exposures to biotic stress (e.g. nematode and Botrytis cinerea) and abiotic stress (e.g. salt, genotoxic, wounding, drought and oxidative stress). Slight defects in seed mucilage extrusion (PubMed:21362134, PubMed:21402796). Ectopic expression of AGAMOUS, leading to the replacement of sepals by carpels and stamens and of petals by stamens (PubMed:15277686). Wide and serrated vegetative leaf lamina, narrow cauline leaves, large palisade cells and reduced fertility (PubMed:15208345). In plants lacking both LUG and LUH, embryo lethality and abnormal flowers (PubMed:18390806). Enhance the polarity and growth defects of fil yab3 and luh/+ lug mutant leaves, being partially abaxialized (PubMed:19837869).