Ribosomal RNA gene repeat units in rice embryos

Abstract

The hybridization of 32P-labeled 25 S, 17 S and 5.8 S rRNAs with the discrete EcoRI, BglII, or BamHI 8.8-kb band from the rice variety IR20 DNA showed the presence of EcoRI, BglII, or BamHI families of tandemly repeated rDNA units. The BamHI digestion of rice DNA also produced 3.8- and 5.0-kb bands which are derived from the major 8.8-kb BamHI fragment. The 3.8-kb DNA cloned in pBR322 at the BamHI site, hybridized pos. with 25 S, 17 S and 5.8 S rRNAs sep., showing the presence of complementary sequences for these rRNAs. The partial nucleotide sequences of the 3.8-kb restriction fragments were identical with the rRNA gene sequences of rice variety Mangetsumochi, with some deletions, addns., and substitutions in the 17 S and 25 S rRNA genes in rice variety IR20. Nucleotide sequence anal. showed that the rRNA genes are organized in the order 17 S-5.8 S-25 S.