Beyond omics: establishing new nematode model systems
Abstract The transition from costly sexual to asexual (parthenogenetic) reproduction is rare in animals. It has many implications on the biology of animals, including on their development and genome structure, where systems have to drastically and quickly change to allow for reproduction without male input. Nevertheless, in nematodes we find several genera with manyparthenogenetic species each, such as in Plectus,Meloidogyne,Acrobeloides, or Panagrolaimus. Oddly, themodel genus Caenorhabditis appears to be void of anyparthenogens, despite the presence of several hermaphroditesamong the ~50 or so identified species. Thus, to understandthe genomic and developmental consequences of life withoutsex, we cannot rely on the model species C.elegans, nor anyof its congeners.
Panagrolaimussp. PS1159 is a non-parasitic nematodeexhibiting parthenogenetic reproduction and we are establishing the species to comparatively study evolution, biodiversity and alternative reproduction strategies. Here, we demonstrate the succesful application of the CRISPR/Cas9 system for genome editing in the species. Using themicroinjection method and modifying published protocolsfrom C.elegansand P.pacificus we induced mutations in theorthologue of unc-22 in Panagrolaimussp. PS1159. We are now in the process of identifying knock-out targets tostudy egg-activation and axis determination in the absence ofsperm in the parthenongen. Further optimising theCRISPR/Cas9 protocol, we aim to functionally analyse keygenes not only in Panagrolaimus sp. PS1159, but in a range ofspecies across the tree.