Transcriptional corepressor. May repress the expression of root-promoting genes in the top half of the embryo to allow proper differentiation of the shoot pole during the transition stage of embryogenesis. Regulates the expression of PLT1 and PLT2. Negative regulator of jasmonate responses. Negative regulator of auxin responses. Negative regulator of multiple floral organ identity genes (PubMed:23034631). Required for ovule development (PubMed:25378179). Tetramer (PubMed:26601214). Homodimer (PubMed:28698367). Interacts (via the LisH domain) with WUS (via the C-terminal domain) (PubMed:16461579). Interacts with NINJA/AFPH2 (PubMed:20360743, PubMed:24416306). Interacts with IAA1; IAA2; IAA3; IAA4; IAA6; IAA8; IAA9; IAA11; IAA13; IAA14; IAA17; IAA18; IAA26; IAA27 AND IAA28 (PubMed:18258861). Interacts (via the LisH domain) with IAA12/BDL (via domain I) (PubMed:18258861). Can form a complex with IAA12 and ARF5 (PubMed:20360743). Interacts with AP2 (via EAR motif) and HDA19 (PubMed:23034631). Interacts with TIFY5A/JAZ8 (via EAR motif) (PubMed:22327740). Interacts with SPEAR3/TIE1 (PubMed:23444332). Interacts with SPL (via EAR motif) (PubMed:25527103, PubMed:25378179). Interacts with ZAT2 and ZAT3 (via the EAR motif) (PubMed:24876252). Interacts with JAZ13 (via EAR motif) (PubMed:25846245, PubMed:16461579, PubMed:18258861, PubMed:20360743, PubMed:22327740, PubMed:23034631, PubMed:23444332, PubMed:24416306, PubMed:24876252, PubMed:25378179, PubMed:25527103, PubMed:26601214). Interacts with GIR1 and GIR2 (PubMed:28526412). Expressed in embryo and in extraembryonic tissues (PubMed:16763149). Expressed in inflorescences, flowers, floral meristems, developing anthers and ovules (PubMed:16461579). Detected in the vascular tissues, shoot apical meristem, cotyledons and young leaves (PubMed:23444332). Expressed ubiquitously in the pistils, stamens and pollens (PubMed:25378179). Expressed in the embryo proper during early embryogenesis and in the developing vasculature in later stages (PubMed:16763149). Expressed dinamically in the proximal region and in the nucellus during ovule development and mainly observed in the nucellus in mature ovules (PubMed:25378179). The N-terminal TOPLESS domain (TPD) (1-209) binds directly to a 12-amino acid LxLxL EAR motif peptide. No visible phenotype, due to the redundancy with the other TPR proteins. The tpl-1 gain-of-function allele is suppressed by mutations in the histone acetyltransferase HAG1 gene. The tpl-1 gain-of-function allele suppresses developmental defects in IAA12/BDL mutants.