Tobacco genes regulated during the hypersensitive response (HR) to infection by tobacco mosaic viruses were screened by differential display and one particular clone with a rapid expression profile was selected and further characterized. The obtained cDNA encoded a polypeptide of 205 amino acids with an apparent molecular mass of 23 kDa and a pI of 10.37 and production of a GFP fusion protein revealed localization in the cytoplasm. Transcripts of the clone were strongly induced in leaves 3 h after HR onset, and 10 min after mechanical wounding, as well as by treatment with jasmonic and salicylic acids. The induction profile satisfies the definition of pathogenesis-related (PR), and the protein was designated as NtPRp23. Database searches indicated the presence of similar proteins in Arabidopsis and rice, but with functions yet to be assigned. Our results point to the existence of a novel PR protein family in tobacco plants.