Involved in lipid metabolism and lipid droplet (LD) morphology, number, and size. Supports the formation of small-sized LDs and modulates triacylglycerol accumulation. Induces probably a reorganization of the endoplasmic reticulum into LD-forming domains. Localized to the lipid droplet-forming sites. Expressed in seeds, seedlings, leaves, stems and roots. Not detected in flowers. Belongs to the seipin family.