Cellular responses to compound stress induced by atmospheric-pressure plasma in fission yeast.

The stress response is one of the most fundamental cellular processes. Although the molecular mechanisms underlying responses to a single stressor have been extensively studied, cellular responses to multiple stresses remain largely unknown. Here, we characterized fission yeast cellular responses to a novel stress inducer, non-thermal atmospheric-pressure plasma. Plasma irradiation generates ultraviolet radiation, electromagnetic fields, and a variety of chemically reactive species simultaneously, and thus can impose multiple stresses on cells. We applied direct plasma irradiation to fission yeast and showed that strong plasma irradiation inhibited fission yeast growth. We demonstrated that mutants lacking sep1 and ace2, both of which encode transcription factors required for proper cell separation, were resistant to plasma irradiation. Sep1-target transcripts were downregulated by mild plasma irradiation. We also demonstrated that plasma irradiation inhibited the target of rapamycin kinase complex 1 (TORC1). These observations indicate that two pathways, namely the Sep1-Ace2 cell separation pathway and TORC1 pathway, operate when fission yeast cope with multiple stresses induced by plasma irradiation.