1. The entomopathogenic nematodeSteinernema hermaphroditumis a self-fertilizing hermaphrodite and a genetically tractable system for the study of parasitic and mutualistic symbiosis
- Author
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Hillel T. Schwartz, Chieh-Hsiang Tan, Paul W. Sternberg, and Mengyi Cao
- Subjects
Genetics ,Symbiosis ,biology ,Xenorhabdus griffiniae ,Genetic model ,medicine ,Xenorhabdus ,Entomopathogenic nematode ,Mating ,biology.organism_classification ,medicine.disease_cause ,Photorhabdus ,Symbiotic bacteria - Abstract
Entomopathogenic nematodes, includingHeterorhabditisandSteinernema, are parasitic to insects and contain mutualistically symbiotic bacteria in their intestines (PhotorhabdusandXenorhabdus,respectively) and therefore offer opportunities to study both mutualistic and parasitic symbiosis. The establishment of genetic tools in entomopathogenic nematodes has been impeded by limited genetic tractability, inconsistent growthin vitro, variable cryopreservation, and low mating efficiency. We obtained the recently describedSteinernema hermaphroditumstrain CS34 and optimized itsin vitrogrowth, with a rapid generation time on a lawn of its native symbiotic bacteriaXenorhabdus griffiniae. We developed a simple and efficient cryopreservation method. Previously,S. hermaphroditumisolated from insect hosts was described as first-generation hermaphroditic and second-generation gonochoristic. We discovered that CS34, when grownin vitro,produced consecutive generations of autonomously reproducing hermaphrodites accompanied by rare males. We performed mutagenesis screens inS. hermaphroditumthat produced mutant lines with visible and heritable phenotypes. Genetic analysis of the mutants demonstrated that this species reproduces by self-fertilization rather than parthenogenesis and that its sex is determined chromosomally. Genetic mapping has thus far identified markers on the X chromosome and three of four autosomes. We report thatS. hermaphroditumCS34 is the first consistently hermaphroditic entomopathogenic nematode and is suitable for genetic model development to study naturally occurring mutualistic symbiosis and insect parasitism.
- Published
- 2021