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Published December 11, 2023 | Accepted
Journal Article Open

Molecular identification of a peroxidase gene controlling body size in the entomopathogenic nematode Steinernema hermaphroditum


The entomopathogenic nematode Steinernema hermaphroditum was recently rediscovered and is being developed as a genetically tractable experimental system for the study of previously unexplored biology, including parasitism of its insect hosts and mutualism with its bacterial endosymbiont Xenorhabdus griffiniae. Through whole-genome re-sequencing and genetic mapping we have for the first time molecularly identified the gene responsible for a mutationally defined phenotypic locus in an entomopathogenic nematode. In the process we observed an unexpected mutational spectrum following EMS mutagenesis in this species. We find that the ortholog of the essential C. elegans peroxidase gene skpo-2 controls body size and shape in S. hermaphroditum. We confirmed this identification by generating additional loss-of-function mutations in the gene using CRISPR-Cas9. We propose that the identification of skpo-2 will accelerate gene targeting in other Steinernema entomopathogenic nematodes used commercially in pest control, as skpo-2 is X-linked and males hemizygous for loss of its function can mate, making skpo-2 an easily recognized and maintained marker for use in co-CRISPR.

Copyright and License

© The Author(s) 2023. Published by Oxford University Press on behalf of The Genetics Society of America. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/pages/standard-publication-reuse-rights)


We thank Erich Schwarz for generously providing early access to unpublished versions of the S. hermaphroditum genome and its annotation; Jennifer Heppert and Heidi Goodrich-Blair for unpublished HGB2511 sequence; Heenam Park and Tsui-Fen Chou for CRISPR reagents and advice; Mengyi Cao for information about Steinernema CRISPR; Barbara Perry, Wilber Palma, and Stephanie Nava for technical assistance; WormBase and WormBase ParaSite for C. elegans and Steinernema genome information; Mona Shagholi of the Caltech Mass Spectrometry service center; and Daniel Semlow and Anton Gartner for advice about the effects of EMS mutagenesis. Some strains were provided by the CGC, funded by P40 OD010440.


This work was supported by NSF-EDGE grant 2128267 (to PWS) and Caltech's Center for Evolutionary Science (CES) and Center for Environmental Microbial Interactions (CEMI). This research benefited from the use of instrumentation made available by the Caltech CCE Multiuser Mass Spectrometry Laboratory, enabled by funds from DOW Next Generation Instrumentation.


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Additional details

December 21, 2023
January 9, 2024