Cloning and characterisation of a ribosomal RNA gene repeat unit from groundnut

Characterisation of a ribosomal RNA gene repeat unit (rDNA) was carried out on groundnut, Arachis hypogaea L. The rDNA was cloned, a restriction map constructed and the 5.8S and internal transcribed spacer (ITS1 and ITS2) regions were completely sequenced while the 18S and 25S regions were partially sequenced. The restriction map and the sequences were compared with published maps and sequences from other crops. The cloned groundnut rDNA is about 12 kb in size with approximately 6 kb of intergenic spacer (IGS). The unique HindIII site in the IGS and two EcoRI and four BamHI sites in the transcribed region are features it shares with other legumes, while the presence of four of the five XbaI sites in the IGS region is its distinguishing feature.