Ubiquitin receptor that limits final seed and organ size by restricting the period of cell proliferation. May act maternally to control seed mass (PubMed:18483219, PubMed:24045020). Acts synergistically with DA2 to regulate seed size. Functions synergistically with DA2 to restrict cell proliferation in the maternal integuments of ovules and developing seeds (PubMed:24045020). Functions antagonistically in a common pathway with UBP15 to regulate seed size. Associates physically with UBP15 and modulates the stability of UBP15, which promote cell proliferation in the integuments of ovules and developing seeds (PubMed:24585836). Functions as peptidase and cleaves the N-terminal sequence of E3 ubiquitin-protein ligases BB and DA2 in a ubiquitin-dependent manner. Cleaves the deubiquitinating enzyme UBP15, which promotes cell proliferation, and the transcription factors TCP15 and TCP22, which promote cell proliferation and repress endoreduplication (PubMed:28167503). Involved in the promotion of leaf senescence, in addition to its function in restricting plant growth (PubMed:28003326). Acts redundantly with DAR1 and DAR2 to regulate endoreduplication during leaf development. Together with DAR1 and DAR2, modulates the protein stability of the transcription factors TCP14 and TCP15, which repress endoreduplication by directly regulating the expression of cell-cycle genes (PubMed:25757472). Interacts with ubiquitin (PubMed:18483219, PubMed:25757472). Interacts (via C-terminus) with DA2 (PubMed:24045020). Interacts with BB (PubMed:28167503). Interacts with UBP15 (PubMed:24585836). Interacts with TCP14 and TCP15 (PubMed:25757472). Highly expressed during the early stages of leaf, petal, integument, and embryo formation and fade away later in petal and leaf development. Induced by abscisic acid (ABA). The UIM domains bind molecules modified by monoubiquitin or ubiquitin chains and promote coupled monoubiquitination. Ubiquitinated at LYS-95, LYS-221, LYS-348, LYS-376, LYS-381, LYS-391, LYS-474, LYS-475 and LYS-519 by the E3 ubiquitin-protein ligases BB and DA2. No visible phenotype. 'Da' means 'large' in Chinese (PubMed:18483219). Plants overexpressing DA1 exhibit early senescence (PubMed:28003326). The predicted gene has been split into 2 genes: At1g19270 and At1g19290.