This invention relates to isolated polynucleotides encoding WUS polypeptides. The invention further provides isolated WUS polypeptides. The invention also provides methods of using the polynucleotides to modulate the level of WUS, improve transformation efficiency, to stimulate plant cell growth, including stem cells, to stimulate organogenesis, to stimulate somatic embryogenesis, to induce apomixis, and to provide a positive selection for cells comprising the polynucleotide. The invention also relates to cells, plants and seeds comprising the polynucleotides of the invention or produced by the methods of the invention.