ena-STUDY-MAX PLANCK INSTITUTE FOR DEVELOPMENTAL BIOLOGY-06-06-2017-09:19:08:272-515
Gain and loss of small RNA classes - characterization of small RNAs in the parasitic nematode family Strongyloididae
The nematode family Strongyloididae is of particular interest because it contains important parasites of medical and veterinary relevance. In addition, species of this family can form parasitic and free-living generations and it also occupies an interesting phylogenetic position within the nematodes. Nematodes differ in several ways from other taxa with respect to their small non-coding RNAs. Recent comparative studies revealed that there is also considerable variability within the nematodes. However, no Strongyloididae species or close relative was included in these studies. We characterized the small RNAs of two developmental stages of three different Strongyloididae species and compared them with the well-studied free-living nematodes Caenorhabditis elegans and Pristionchus pacificus.Strongyloididae have conserved and taxon specific micro RNAs, many of which are differentially regulated between the two developmental stages. We identified a novel class of around 27 nucleotide long RNAs starting with 5'G or A (27GA RNAs), of which a large fraction have the potential to target transposable elements. These RNAs most likely have triphosphates at their 5' ends and are therefore presumably synthesized by RNA dependent RNA polymerases. In contrast to C. elegans but similarly to some other nematode taxa, Stronglyoididae have no piRNAs, nor do their genomes encode Argonaute proteins of the Piwi family. Finally, we attempted but failed to detect circulating parasite small RNAs in the blood of hosts.
The nematode family Strongyloididae is of particular interest because it contains important parasites of medical and veterinary relevance. In addition, species of this family can form parasitic and free-living generations and it also occupies an interesting phylogenetic position within the nematodes. Nematodes differ in several ways from other taxa with respect to their small non-coding RNAs. Recent comparative studies revealed that there is also considerable variability within the nematodes. However, no Strongyloididae species or close relative was included in these studies. We characterized the small RNAs of two developmental stages of three different Strongyloididae species and compared them with the well-studied free-living nematodes Caenorhabditis elegans and Pristionchus pacificus.Strongyloididae have conserved and taxon specific micro RNAs, many of which are differentially regulated between the two developmental stages. We identified a novel class of around 27 nucleotide long RNAs starting with 5'G or A (27GA RNAs), of which a large fraction have the potential to target transposable elements. These RNAs most likely have triphosphates at their 5' ends and are therefore presumably synthesized by RNA dependent RNA polymerases. In contrast to C. elegans but similarly to some other nematode taxa, Stronglyoididae have no piRNAs, nor do their genomes encode Argonaute proteins of the Piwi family. Finally, we attempted but failed to detect circulating parasite small RNAs in the blood of hosts.