GSE189061
Small RNA pathways in the nematode Ascaris in the absence of piRNAs
Small RNA pathways play diverse regulatory roles in the nematode C. elegans. However, our  understanding of small RNA pathways, their conservation, and their roles in other nematodes is limited.  Here, we analyzed small RNA pathways in the parasitic nematode Ascaris. Ascaris has ten Argonautes  with five worm-specific Argonautes (WAGOs) that are associated with secondary 5'-triphosphate small  RNAs (22-24G-RNAs). These Ascaris WAGOs and their small RNAs target repetitive sequences (WAGO-1, WAGO-2, WAGO-3, and NRDE-3) or mature mRNAs (CSR-1, NRDE-3, and WAGO-3) and are similar  to the C. elegans mutator, nuclear, and CSR-1 small RNA pathways. Ascaris CSR-1 likely functions to  “license” gene expression in the absence of an Ascaris piRNA pathway. Ascaris ALG-4 and its associated  26G-RNAs target and appear to repress specific mRNAs during meiosis in the testes. Notably, Ascaris  WAGOs (WAGO-3 and NRDE-3) small RNAs change their targets between repetitive sequences and  mRNAs during spermatogenesis or in early embryos illustrating target plasticity of these WAGOs. We  provide a unique and comprehensive view of mRNA and small RNA expression throughout nematode  spermatogenesis that illustrates the dynamics and flexibility of small RNA pathways. Overall, our study  provides key insights into the conservation and divergence of nematode small RNA pathways. Overall design: Examination of small RNAs associated with 7 Argonaut proteins in early embryo, female/male germline and different male germline regions of parasitic worm Ascaris.