Microcystin-RR （MC-RR） has been suggested to induce apoptosis in tobacco BY-2 cells through mitochondrial dysfunction including the loss of mitochondrial membrane potential . TO further elucidate the mechanisms involved in MC-RR induced apoptosis in tobacco BY-2 cells, we have investigated the role of mitochondrial electron transport chain （ETC） as a potential source for reactive oxygen species （ROS）. Tobacco BY-2 cells after exposure to MC-RR （60 mg/L） displayed apoptotic changes in association with an increased production of ROS and loss of Am. All of these adverse effects were significantly attenuated by ETC inhibitors including Rotenone （2 μmol/L, complex I inhibitor） and antimycin A （0.01 μmol/L, complex III inhibitor）, but not by thenoyltrifluoroacetone （S μmol/L, complex Ⅱinhibitor）. These results suggest that rnitochondrial ETC plays a key role in mediating MC-RR induced apoptosis in tobacco BY-2 cells through an increased mitochondrial production of ROS.
