Retrotransposons are mobile genetic elements that accomplished transposition via an RNA intermediate. These elements can be transcriptionally activated by stress factors, such as UV light, ozone, pathogens, wounding and drought. A red alga, porphyra yezoensis has recently been recognized as a model plant for fundamental and applied study in marine biological science. In this paper, pulsed streamer-like discharge in liquid was used as a new stress condition, and the transcription level of a copia-like retrotansposon gene PyRE1 of a red alga, porphyra yezoensis was investigated. From the results of reverse transcription-polymerase chain reaction (RT-PCR) experiments, the transcription of PyRE1 was activated by applying pulsed streamer-like discharge. The results suggest that pulsed streamer-like discharge in liquid can be used as a new stress condition to activate retrotransposon genes and can provide a useful tool for insertion mutagenesis and genome research in biology field.