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Abstract

Developmental plasticity enables the production of alternative phenotypes in response to different environmental conditions. Work over the last decade in the model nematode Pristionchus pacificus has uncovered several genes which are required for alternative mouth-form phenotypes. Here, we collated these data into a gene regulatory network (GRN), and performed developmental transcriptomics across different environmental conditions, genetic backgrounds, and mouth-form mutants to assess the regulatory mechanisms underlying mouth-form plasticity. First, we show that expression of only a subset of previously identified mouth-form genes is sensitive to environmental conditions. Further, a comparison between strains and species with different mouth-form ratios reveals distinct patterns from environmental regulation. Surprisingly, our analyses suggest different roles for the two previously identified switch genes, eud-1 and seud-1/Ppa-sult-1. One appears to be an environmental sensor, while the other appears to set the default mouth form for a given genetic background. Finally, a comprehensive analysis of all sample types (environmental, mutant, strain, and species) identifies common pathways that are involved in regulating mouth-form development. Collectively, our temporal analyses of a plasticity GRN provides a testable set of rules for the regulation of developmental plasticity.