Nucleotide sequence of the 17S-25S spacer region from rice rDNA.

The nucleotide sequence of a spacer region between rice 17S and 25S rRNA genes (rDNAs) has been determined. The coding regions for the mature 17S, 5.8S and 25S rRNAs were identified by sequencing terminal regions of these rRNAs. The first internal transcribed spacer (ITS1), between 17S and 5.8S rDNAs, is 194-195 bp long. The second internal transcribed spacer (ITS2), between 5.8S and 25S rDNAs, is 233 bp long. Both spacers are very rich in G+C, 72.7% for ITS1 and 77.3% for ITS2. The 5.8S rDNA is 163-164 bp long and similar in primary and secondary structures to other eukaryotic 5.8S rDNAs. The 5.8S rDNA is capable of interacting with the 5' terminal region of 25S rDNA.