alpha-Tomatine, the major saponin in tomato, induces programmed cell death mediated by reactive oxygen species in the fungal pathogen Fusarium oxysporum.
The tomato saponin alpha-tomatine has been proposed to kill sensitive cells by binding to cell membranes followed by leakage of cell components. However, details of the modes of action of the compound on fungal cells are poorly understood. In the present study, mechanisms involved in alpha-tomatine-induced cell death of fungi were examined using a filamentous pathogenic fungus Fusarium oxysporum. alpha-Tomatine-induced cell death of F. oxysporum (TICDF) occurred only under aerobic conditions and was blocked by the mitochondrial F(0)F(1)-ATPase inhibitor oligomycin, the caspase inhibitor D-VAD-fmk, and protein synthesis inhibitor cycloheximide. Fungal cells exposed to alpha-tomatine showed TUNEL-positive nuclei, depolarization of transmembrane potential of mitochondria, and reactive oxygen species (ROS) accumulation. These results suggest that TICDF occurs through a programmed cell death process in which mitochondria play a pivotal role. Pharmacological studies using inhibitors suggest that alpha-tomatine activates phosphotyrosine kinase and monomeric G-protein signaling pathways leading to Ca(2+) elevation and ROS burst in F. oxysporum cells.
Ito
Shin-Ichi
S
Department of Biological and Environmental Sciences, Faculty of Agriculture, Yamaguchi University, Yamaguchi, Yamaguchi, Japan. shinsan@yamaguchi-u.ac.jp
Ihara
Takashi
T
Tamura
Hideyuki
H
Tanaka
Shuhei
S
Ikeda
Tsuyoshi
T
Kajihara
Hiroshi
H
Dissanayake
Chandrika
C
Abdel-Motaal
Fatma F
FF
El-Sayed
Magdi A
MA
D000935:Antifungal Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D020013:Calcium Signaling / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005670:Fusarium / Q000187:drug effects* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D018551:Solanum lycopersicum / Q000737:chemistry; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism / Q000494:pharmacology*; D012503:Saponins / Q000737:chemistry / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects; D014053:Tomatine / Q000031:analogs & derivatives* / Q000494:pharmacology
D000935:Antifungal Agents; D017382:Reactive Oxygen Species; D012503:Saponins; C484751:alpha-tomatine; D014053:Tomatine; D011505:Protein-Tyrosine Kinases; D019204:GTP-Binding Proteins