DNA helicase that acts as an essential component of the spindle assembly checkpoint (By similarity). Plays an indispensable role in the development of seed endosperm (PubMed:25327517). Is required to secure sister chromosome separation during endosperm syncytial mitosis, which involves extremely rapid free nuclear cycles (PubMed:25327517). Localizes to the cytoplasm during interphase, but moves to the chromosome arms during mitosis. Expressed in ovaries, roots, shoots and leaves. Lack of seed endosperm, alteration of ovary and embryo shape, reduced root and plant growth, but fertile plants. Belongs to the SNF2/RAD54 helicase family.