In plants, the outer epidermal cell wall and cuticle presents a semipermeable barrier that maintains the external integrity of the plant and regulates the passage of various classes of molecules into and out of the organism. During vegetative development, the epidermal cells remain relatively inert, failing to respond to wounding or grafting. During reproductive development and fertilization, however, the epidermis is developmentally more labile and participates in two types of contact-mediated cell interactions: organ fusion and pollen hydration. Here we describe the isolation and characterization of one gene whose product normally functions in blocking both types of epidermal cell interactions during vegetative development: the FIDDLEHEAD gene. As suggested by previous biochemical analyses, the gene encodes a protein that is probably involved in the synthesis of long-chain lipids found in the cuticle and shows similarity to a large class of genes encoding proteins related to beta-ketoacyl-CoA synthases and chalcone synthases. In situ hybridization reveals an epidermal pattern of expression consistent with a role for this protein in the synthesis of lipid components that are thought to localize extracellularly and probably modify the properties of the cuticle.