THE MOLECULAR DIVERSITY OF THE 5S RIBOSOMAL-RNA GENE IN BARLEY (HORDEUM-VULGARE)

The 5S rDNA genes from several accessions of cultivated barley, Hordeu m vulgare L., were amplified by the polymerase chain reaction, cloned, and sequenced. Analysis of the aligned sequences, followed by princip al coordinate analysis, support the recognition of at least two distin ct classes of 5S rDNA genes. The short repeat class corresponds to the 300-bp tandem repeat defined by E.V. Ananiev as containing several TA G repeating units. The long repeat class contains long tandem repeats and lacks the TAG repeating unit. Sequences in each class can be furth er subdivided, with the long repeat class containing two groups and th e short repeat class containing two and possibly three groups. These r esults suggest that in cultivated barley the sequence diversity found within the 5S rDNA nontranscribed spacer region may be encoded by thre e or more loci and may be useful for phylogenetic analyses provided th at orthology can be established.