Table 1. The small-RNA machinery of representative eukaryotes.
| Species | Ago | Piwi | Dicer | Drosha | Pasha | Hen1 |
|---|---|---|---|---|---|---|
| Homo sapiens | 4 | 4 | 1 | 1 | 1 | 1 |
| Drosophila melanogaster | 2 | 3 | 2 | 1 | 1 | 1 |
| Caenorhabditis elegans* | 5 | 3 | 1 | 1 | 1 | 1 |
| Nematostella vectensis† | 3 | 3 | 2 | 1 | 1 | 1 |
| Trichoplax adhaerens† | 1 | 0‡ | 5 | 1 | 0§ | 0‡ |
| Amphimedon queenslandica† | 2 | 3 | 4 | 1 | 1 | 2 |
| Monosiga brevicollis | 0‡ | 0‡ | 0‡ | 0 | 0 | 0‡ |
| Saccharomyces cerevisiae | 0‡ | 0‡ | 0‡ | 0 | 0 | 0‡ |
| Schizosaccharomyces pombe║ | 1 | 0‡ | 1 | 0 | 0 | 0‡ |
| Arabidopsis thaliana | 10 | 0‡ | 4 | 0 | 0 | 2 |
| Physcomitrella patens | 6 | 0‡ | 5 | 0 | 0 | 1 |
| Chlamydomonas reinhardtii | 2 | 0‡ | 3 | 0 | 0 | 1 |
*
Omitted is a nematode-specific clade of proteins related to the Ago and Piwi protein families but distinct from both27.
†
Protein sequences are listed in Supplementary Data 3.
‡
Inferred loss based on presence in earlier-diverging lineages.
§
Inferred loss based on presence in earlier-diverging lineages when assuming that Amphimedon diverged before Trichoplax (Supplementary Discussion).
║
Ago and Dicer, but not Piwi, Drosha, Pasha or Hen1, were also identified in each of the additional fungal species examined (Aspergillus nidulans, Neurospora crassa and Sclerotinia sclerotiorum).