ROS Is Necessary for Dormancy Breaking in Fission Yeast Spores, While Its Downregulation by Sod1 Is Crucial for Later Events

ABSTRACT

Fission yeast spores adapt to nutrient deprivation by entering a dormant state. Upon exposure to nutrients, spores initiate germination, followed by proliferation. However, the molecular mechanisms that govern germination remain poorly understood. Here we demonstrate that an optimal level of reactive oxygen species (ROS) facilitates germination progression, with the level decreasing as germination proceeds. Observations using ROS fluorescent probes indicated that intracellular ROS was relatively high in dormant spores compared to germinating spores, as it decreased in response to germination cues. Nonetheless, artificially reducing ROS levels in dormant spores with a drug inhibited the initiation of germination, indicating that an adequate level of ROS is required to initiate germination. In later stages, however, a reduction in ROS is necessary because spores lacking the antioxidant enzyme Sod1 (copper‐zinc superoxide dismutase 1) fail to reduce ROS during these stages, hindering subsequent development. Thus, we conclude that intracellular ROS levels, which varied in accordance with the chronological sequence of spore germination, regulate the germination process.