Involved in growth and development through its role in cytokinesis and polarized cell expansion. Required for plasma membrane internalization. May function in clathrin-mediated membrane trafficking, including plasma membrane endocytosis, essential to both cytokinesis and cell expansion. Colocalized with clathrin at the plasma membrane. A number of isoforms are produced. According to EST sequences. Expressed in the mature region of the primary root, tips of short, young lateral roots, guard cells in the epidermis of cotyledons and rosette leaves, the socket cells surrounding the base of trichomes and hydathodes of fully expanded rosette leaves. Defects in seedling development, root elongation, leaf expansion, flower morphogenesis and fertility due to defective cytokinesis in epidermal cells.