The histidine decarboxylase (HDC) gene of tetrahymena pyriformis is similar to the mammalian one. A study of HDC expression

RNA was isolated from Tetrahymena pyriformis GL and using human histidine d ecarboxylase (HDC) gene primers, the RT-PCR product was sequenced. A fracti on containing 207 base pairs was compared to the published sequences of pro karyotic and mammalian (rat, mouse and human) HDC cDNA (exons). The HDC-cDN A fraction of Tetrahymena was similar to the mammalian cDNA-s and it was co mpletely different from the prokaryotic HDC-gene. The results indicate the presence of a mammalian-like HDC-gene already in a unicellular eukaryote or ganism and demonstrates also that the divergence of the prokaryotic-eukaryo tic common gene took place already at this low evolutionary level.