Disclosed are mutant CDK inhibitor (CKI) polypeptides having dominant negativeantagonist activity against wild-type CKI proteins, as well as relatedcompositions, including nucleic acids and vectors encoding the mutant CKIpolypeptides and transformed host cells and transgenic plants comprising suchnucleic acids and vectors. Also disclosed are related methods for using themutant proteins to modulate cell division in cells, particularly plant cells
