Transcriptional corepressor. Activates TIR-NB-LRR R protein-mediated immune responses through repression of negative regulators such as CNGC2/DND1 (PubMed:20647385). Negative regulator of jasmonate responses (By similarity). Tetramer (PubMed:26601214). Interacts with SNC1 (via TIR domain) and HDA19 (PubMed:20647385). Interacts with SPL (via EAR motif) (PubMed:25527103, PubMed:25378179). Interacts with SPEAR3/TIE1 (PubMed:23444332). Binds to and corepresses GAF1/IDD2 (PubMed:25035403). Highly expressed in stamen primordium, microsporocyte, ovule primordium and megasporocyte during sporogenesis. The N-terminal TOPLESS domain (TPD) (1-209) binds directly to a 12-amino acid LxLxL EAR motif peptide. Partially suppresses the constitutive disease resistance phenotype of the snc1 mutant. Overexpression of TPR1 leads to constitutive activation of defense responses.