Phylogenetic tree based on PtaRNA1 seed alignment. Class of the “host” species is shown by the symbols on the right hand side. Numbers indicate bootstrap values of the inner nodes.
Homologs of the "Plasmid transferred anti-sense RNA" (PtaRNA1) were found in both beta- and gamma-proteobacteria. In all cases the ptaRNA1 is located anti-sense to a short protein coding gene, in Xanthomonas campestris pv. vesicatoria annotated as XCV2162. Both molecules show a very erratic phylogenetic distribution and appear only in combination. Interestingly, is the phylogenetic distribution of the ptaRNA1 not congruent with the phylogeny of the “host” species, indicating that ptaRNA1 undergoes frequent horizontal gene transfer. These observations are in accordance with the described Type 1 Toxin-Antitoxin systems. In these two molecule systems -- the expression of a toxic protein is regulated by a small non-coding RNA. Type 1 Toxin-Antitoxin loci are frequently found in both prokaryotic chromosomes and plasmids, and are reviewed in more detail. [1][2][3] PtaRNA1 exhibits a conserved secondary structure which is very similar to that of the FinP anti-sense RNA. [4]
