Submitted to: American Phytopathological Society
Publication Type: Abstract Only
Publication Acceptance Date: April 13, 2001
Publication Date: N/A
Technical Abstract: Loofah witches' broom (LfWB) phytoplasma is the only described member of phylogenetic group 16SrVIII. For analysis of the rRNA operons of LfWB phytoplasma, 1.8 kbp DNA sequences containing most of the 16S rRNA gene, the 16S-23S rRNA spacer region, and the 5'-end of the 23S rRNA gene were cloned and subjected to RFLP and nucleotide sequence analyses. The results showed that the LfWB phytoplasma genome contained two sequence-heterogeneous rRNA operons, which we termed rrnA (GenBank no. AF248956) and rrnB (GenBank no. AF353090), respectively. The spacer region of operon rrnA contained a complete tRNA-Ile gene. In contrast, operon rrnB was characterized by 43 base deletions and a single base substitution in the tRNA-Ile gene and a 10-base deletion in the spacer region immediately upstream of the tRNA-Ile gene. This altered structure of operon rrnB is probably due to recombination and base misincorporation. The tRNA-Ile gene of LfWB rrnB is the first known example of a partially deleted, nonfunctional gene in a phytoplasma genome.