A. Growth phenotypes of mitochondrial fusion (fzo1-1) and division (Δdnm1) mutants. B. Chemical structure of the quinazolinone, mdivi-1. Important structural features are highlighted in red and were determined by comparing the efficacies of mdivi-1 like compounds shown in Figure 2. C. mdivi-1 suppresses the growth defect of mitochondrial fusion mutants, fzo1-1 and mgm1-5 at the restrictive temperature . D and E. mdivi-1 causes the formation of mitochondrial net-like structures (E, right panel, mdivi-1; left panel, DMSO) in Δprd1 Δprd3 yeast cells in a dose-dependent manner (D, representative experiment shown, n ≥ 100). In E, left panel is the DMSO control, right panel is mdivi-1. F. mdivi-1 has no effect on the F-actin cytoskeleton. Mitochondria are in red, and Phalloidin is in green. Left panel: DMSO control cells. Center panel: mdivi-1-treated cells. Right panel: Latrunculin-A and mdivi-1-treated cells. N=mitochondrial nets. Scale bar = 2μ.