Polyadenylation and decay of 26S rRNA as part of Nicotiana tabacum response to cadmium

In contrast to mRNAs, ribosomal RNAs are generally not considered to be polyadenylated. Only a few recent reports describe non-abundant polyadenylated rRNA-related transcripts that have been detected and characterized in yeast and in human cells. Here we depict the phenomenon of 26S rRNA polyadenylation and degradation that was observed in shoots of Nicotiana tabaccum plants grown in the presence of cadmium. Fragments corresponding to 26S rRNA were identified using suppression subtractive hybridization during screening for genes induced in tobacco plants upon a three-week exposure to 15 µM cadmium chloride. Extracts prepared from the above-ground tissues of cadmium-treated tobacco plants were supposed to contain exclusively polyadenylated mRNAs. Surprisingly, numerous polyadenylated fragments matching parts of 26S rRNA were identified and their presence was confirmed by Northern blot and cDNA amplification techniques. To our knowledge this is the first report on rRNA polyadenylation in plants.