Rapid changes in stress-related gene expression after short exposure of Arabidopsis leaves to cold plasma

Cold Atmospheric Plasma (CAP) technology has emerged as a promising tool in various biological applications due to its ability to generate a composite signal comprising reactive oxygen and nitrogen species, ultraviolet radiation, and electromagnetic fields, all while maintaining a stable temperature. Although CAP treatments have demonstrated significant effects on seed germination and plant growth, the direct molecular responses of plants to CAP exposure remain poorly understood. In this study, young Arabidopsis thaliana leaves were exposed to a brief 5- or 30-s localized CAP treatment, resulting in rapid and localized tissue damage without causing lethal effects on the entire plant. Molecular analyses conducted on the entire plant rosette revealed a notable increase in hydrogen peroxide levels, along with the upregulation of stress-related genes, akin to a wound response. Of particular interest, the activation of RelA/SpoT Homolog (RSH) genes encoding proteins that regulate the synthesis of the stress marker (p)ppGpp, also known as alarmone, and playing a major role in the energic regulation of photosynthesis, occurred shortly after CAP exposure. The expression of RSH genes was up-regulated after 5s CAP exposure, while the wound stress marker ZAT12 remained unaffected, highlighting a specific signalling pathway to activate RSH genes. This finding suggests the potential involvement of the alarmone signalling pathway in the plant's response to CAP exposure, thereby opening avenues for further exploration of metabolic pathways and signalling cascades induced by CAP treatment.