To determine their tissue-specific expression, three GRX genes were isolated from ESTs of a "6-hr post-suberization" cDNA library for Solanum tuberosum L cv. Desiree. Transcripts of a CCxC/S type GRX, StGRX1, accumulated to higher levels during the vegetative-growth stage in the leaves, stem, and roots. In contrast, transcripts of a CxxC/S type GRX, StGRX2, accumulated in the reproductive tissues, such as the flower and tuber. Differential expression of these three potato StGRXs suggest specific and unique physiological roles during plant development and in response to environmental cues. Therefore, we propose that StGRX1 is a housekeeping gene, functioning in the rapid defense against various abiotic and biotic stresses, while StGRX2 and -3 are selectively expressed during growth and in response to internal and external signals.