LAUSR

ABSTRACT Genes encoded in nuclear ribosomal DNA (nrDNA), which comprise a multi-family of genes with tandem repeat units, play an important role in nucleolus formation. In the present study, we sequenced and analysed the complete rDNA sequence of an economically important shellfish in Australia, Haliotis rubra. The single rDNA unit measured 9881 base pairs (bp) in length and included the following elements in order: 18S rRNA (1858 bp), internal transcribed spacers (ITS, 756 bp), 28S rRNA (3413 bp) and an intergenic spacer (IGS, 3854 bp). The phylogenetic tree was constructed using abalone ITS sequences; here, the relationship revealed that abalone species within the same region and with same chromosome number tended to cluster within a clade. The positions of putative transcription termination and RNA transcription initiation sites were predicted in the IGS region. A comparative sequence complexity analysis and dot plots revealed a high level of variability in the IGS.