Required for male and female gametogenesis, seed development, and embryo and endosperm development at early stages. Involved in the establishment of bilateral symmetry in the transition from the globular to the heart embryo stage. May act in the frame of a CRL4 complex (PubMed:22447688). Required for proper vegetative growth and organization of the adult plant body. May play a role in hormonal control of plant development (PubMed:23803743). Interacts with DDB1A. Highly expressed in roots. Expressed in cotyledons, leaves, buds and flowers. Expressed in female gametophyte throughout embryo sac development. During pollen development, expressed from meiosis up to the second pollen mitosis, but not at mature (three nucleate) stages. Embryonic lethality when homozygous, due to embryo and endosperm developmental arrest at various stages ranging from the zygote stage to the globular stage. Failure in the fusion of the polar cells in embryo sac development. Plants with a weak allele homozygous for WDR55 display pleiotropic phenotypes in the seedling and adult stages. Belongs to the WD repeat WDR55 family.