XVI International Botanical Congess
In eukaryotes, rRNA genes consist of tandemly repeated rDNA units composed of rRNA coding regions and spacers. rRNA genes are the template for transcription by RNA polymerase I, but for transcription initiation/regulation specific binding proteins (BP) are also necessary. Supposing that the conservative elements present in the intergenic spacer region (IGS) may harbour transcription/processing signals we have compared the IGS sequences for distantly related Solanaceae and found that only some motifs are extremely conserved. HMG-like proteins bind to conservative portion of IGS upstream of TIS, suggesting that they play a role in assembly of the rDNA transcription initiation complex. Other IGS regions also contain specific nuclear protein binding sites which are probably involved in transcription regulation.