IN-VITRO TRANSCRIPTION OF PLANT RNA-POLYMERASE I-DEPENDENT RIBOSOMAL-RNA GENES IS SPECIES-SPECIFIC

An in vitro transcription system derived from tobacco (Nicotiana tabac um) cultured cell (BY-2) nuclei supports transcription of the RNA poly merase I dependent tobacco rRNA gene. The transcription initiation sit e determined in vitro was found at residue A which corresponds to that lying within the consensus sequence surrounding plant pre-rRNA initia tion sites. The tobacco rRNA gene is actively transcribed in the tobac co nuclear extract while the broad bean rRNA gene is inactive in the h eterologous system, indicating that plant RNA polymerase I-dependent t ranscription is species-specific.