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Abstract The ability to translate a single genome into multiple phenotypes, or developmental plasticity, defines how phenotype derives from more than just genes. However, to study the evolutionary targets of plasticity and their evolutionary fates, we need to understand how genetic regulators of plasticity control downstream gene expression. Here, we have identified a transcriptional response specific to polyphenism (i.e., discrete plasticity) in the nematode Pristionchus pacificus. This species produces alternative resource-use morphs—microbivorous and predatory forms, differing in the form of their teeth, a morphological novelty—as influenced by resource availability. Transcriptional profiles common to multiple polyphenism-controlling genes in P. pacificus reveal a suite of environmentally sensitive loci, or ultimate target genes, that make up an induced developmental response. Additionally, in vitro assays show that one polyphenism regulator, the nuclear receptor NHR-40, physically binds to promoters with putative HNF4α (the nuclear receptor class including NHR-40) binding sites, suggesting this receptor may directly regulate genes that describe alternative morphs. Among differentially expressed genes were morph-limited genes, highlighting factors with putative “on–off” function in plasticity regulation. Further, predatory morph-biased genes included candidates—namely, all four P. pacificus homologs of Hsp70, which have HNF4α motifs—whose natural variation in expression matches phenotypic differences among P. pacificus wild isolates. In summary, our study links polyphenism regulatory loci to the transcription producing alternative forms of a morphological novelty. Consequently, our findings establish a platform for determining how specific regulators of morph-biased genes may influence selection on plastic phenotypes.
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Genetic regulators of a resource polyphenism interact to couple predatory morphology and behaviour
Phenotypic plasticity often requires the coordinated response of multiple traits observed individually as morphological, physiological or behavioural. The integration, and hence functionality, of this response may be influenced by whether and how these component traits share a genetic basis. In the case of polyphenism, or discrete plasticity, at least part of the environmental response is categorical, offering a simple readout for determining whether and to what degree individual components of a plastic response can be decoupled. Here, we use the nematodePristionchus pacificus, which has a resource polyphenism allowing it to be a facultative predator of other nematodes, to understand the genetic integration of polyphenism. The behavioural and morphological consequences of perturbations to the polyphenism’s genetic regulatory network show that both predatory activity and ability are strongly influenced by morphology, different axes of morphological variation are associated with different aspects of predatory behaviour, and rearing environment can decouple predatory morphology from behaviour. Further, we found that interactions between some polyphenism-modifying genes synergistically affect predatory behaviour. Our results show that the component traits of an integrated polyphenic response can be decoupled and, in principle, selected upon individually, and they suggest that multiple routes to functionally comparable phenotypes are possible.
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- Award ID(s):
- 2229383
- PAR ID:
- 10567664
- Publisher / Repository:
- The Royal Society
- Date Published:
- Journal Name:
- Proceedings of the Royal Society B: Biological Sciences
- Volume:
- 291
- Issue:
- 2024
- ISSN:
- 1471-2954
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1098/rspb.2024.0153
