The medium-size noncoding RNA transcriptome of , the smallest living eukaryote, reveals a large family of small nucleolar RNAs displaying multiple genomic expression strategies.

The small nucleolar RNAs (snoRNAs), essential for ribosome biogenesis, constitute a major family of medium-size noncoding RNAs (mncRNAs) in all eukaryotes. We present here, for the first time in a marine unicellular alga, the characterization of the snoRNAs family in , the smallest photosynthetic eukaryote. Using a transcriptomic approach, we identified 131 snoRNAs (Ot-snoRNA) distributed in three classes: the C/D snoRNAs, the H/ACA snoRNAs and the MRP RNA.