Expression of rev stimulates production of reactive oxygen species (ROS) in S. pombe cells. Fission yeast strain carrying pYZ1N-rev was grown in selective EMM either in the presence (+T) or absence (−T) of thiamine to suppressor or induce rev gene induction, respectively. a ROS production was detected by addition of a ROS indicator dye (DHE) to the culture medium right before microscopic observation overtime at different times as indicated. An oxygen radical scavenger (TMPO) was also added in separate test tubes but concurrently to test the specific production of ROS. TMPO was added twice during the course of the rev expression. TMPO was first added to the culture at the time of cell inoculation when rev gene expression was induced, and cells were treated again with TMPO when DHE was added to the culture to detect ROS production. DHE DHE-positive cells, DIC cells shown by differential interference contrast. Scale bar 10 μm. b Percentage of ROS-producing cells induced by HIV-1 Rev decreases over time. The % of ROS-producing cells induced by HIV-1 Rev was quantified by counting the numbers of DHE-positive cells over the entire cell population of three independent experiments.