The establishment of transient gene expression systems in the marine red macroalga Porphyra yezoensis has been useful for the molecular analysis of cellular processes in this species. However, there has been no successful report about the expression of foreign genes in other red macroalgae, which has impeded the broader understanding of the molecular biology of these species. We therefore examined whether the P. yezoensis transient gene expression system was applicable to other red macroalgae. The results indicated that a codon-optimized GUS, designated PyGUS, and plant-adapted sGFP(S65T) were successfully expressed under the control of the P. yezoensis PyAct1 promoter in gametophytic cells of six Porphyra species and also in Bangia fuscopurpurea, all of which are classified as Bangiophyceae. In contrast, there were no reporter-expressing cells in the Florideophycean algae examined. These results indicate the availability of PyGUS and sGFP as reporters and the 5' upstream region of the PyAct1 gene as a heterologous promoter for transient gene expression in Bangiophycean algae, which could provide a clue to the efficient expression of foreign genes and transformation in marine red macroalgae.