Acts as a negative regulator of abscisic acid (ABA) response during germination through the ubiquitin-mediated proteolysis of ABI5/DPBF1. Forms a heterodimer with AFP2. Interacts with ABI5/DPBF1, DPBF2, AREB3/DPBF3, ABF1, ABF3/DPBF5 and ABF4/AREB2. Expressed in embryo during the latest stages of seed maturation. Up-regulated by abscisic acid (ABA), glucose and salt. Exhibits slight hypersensitivity to abscisic acid (ABA), salt and osmotic stress. Belongs to the Ninja family.