Activator protein that regulates the ubiquitin ligase activity and substrate specificity of the anaphase promoting complex/cyclosome (APC/C). Required for meristem organization and maintenance of quiescent center identity and stem cells. Protein modification; protein ubiquitination. Associates with the APC/C complex. Interacts with CDC20-1, CDC20-2, CYCA1-1, CYCA1-2, CYCA3-4, CYCB1-1 AND CYCB1-2. Binds to GIG1. Expressed in the root tip, predominantly in the root cap, quiescent center cells, surrounding stem cells and columella. Expressed from late M until late S-early G2 phases. Stunted plants. Impaired root growth and smaller root meristem. FZR2 controls the induction of early rounds of endoreduplication while the remaining rounds may be mediated by FZR1 and FZR3. FZR1 and FZR2 are functional homologs, and their functional divergence in root development arises from the different expression patterns. Belongs to the WD repeat CDC20/Fizzy family.