Comparison of different smORF searches showing the number of smORFs identified in S. cerevisiae , A. thaliana , M. musculus  and D. melanogatser (this study). aThe fraction of smORFs relative to previously annotated protein-coding genes. bThe proportion of smORFs with direct experimental evidence of translation and/or function. Numbers in parentheses are the actual numbers of smORFs tested experimentally. ND, not determined.