Analysis of full-length cDNA libraries from bdelloid rotifers A. ricciae and Philodina sp. revealed a number of cDNAs with a common 23-nt sequence at their 5' ends.
The same DNA segment was found on cDNAs encoding a variety of proteins including structural proteins, metabolic enzymes and regulatory proteins in both bdelloid species. This is diagnostic of spliced leader (SL) RNA-mediated trans-splicing, whereby 5' ends of precursor mRNAs are replaced by a short exon from a small SL RNA (Fig. 1).
The description of SL-mediated trans-splicing in Rotifera extends its representation to at least five metazoan taxa, the others being nematodes, cnidarians, platyhelminths and primitive chordates, making it increasingly probable that this is a phylogenetically widespread and therefore ancient phenomenon.
Bdelloid Rotifer Research Topics:
Pouchkina-Stantcheva, N. N. and Tunnacliffe, A. (2005) Spliced-leader RNA mediated trans-splicing in phylum Rotifera. Mol. Biol. Evol. 22: 1482-1489.