Evaluating the evolution of G. lamblia based on the small nucleolar RNAs identified from Archaea and unicellular eukaryotes.

The evolutionary position of Giardia lamblia has been challenged in recent years. Comparison of the snoRNAs identified from Archaea and unicellular eukaryotes shows that G. lamblia snoRNAs are more similar in most respects to the counterparts identified from Dictyostelium discoideum, Plasmodium falciparum, fungi, and some metazoans, remarkably differently from those of Euglenozoa protozoans. We propose that G. lamblia emerged somewhat later than Trypanosoma and Euglena during the early evolution of "excavata" eukaryotes.