Loss of Arv1p disrupts organelle integrity. Thin section EM of control (A) and arv1Δ strains (B and C). N, nucleus; V, vacuole; pnER and cER, perinuclear and cortical endoplasmic reticulum, respectively; PM, plasma membrane; LD, lipid droplet. The arrows indicate membrane proliferation seen in ARV1 mutants. D, FM4-64 (20 μg/ml) staining of cells.