The Antiquity of Chordate Odorant Receptors Is Revealed by the Discovery of Orthologs in the Cnidarian Nematostella vectensis
Bibliographic record
Abstract
In vertebrates, olfaction is mediated by several families of G protein-coupled receptors (GPCRs) including odorant receptors (ORs). In this study, we investigated the antiquity of OR genes by searching for amino acid motifs found in chordate ORs among the protein predictions from 12 nonchordate species. Our search uncovered a novel group of genes in the cnidarian Nematostella vectensis. Phylogenetic analysis that included representatives from the other major lineages of rhodopsin-like GPCRs showed that the cnidarian genes, the cephalochordate and vertebrate ORs, and a family of genes from the echinoderm, Strongylocentrotus purpuratus, form a monophyletic clade. The taxonomic distribution of these genes indicates that the formation of this clade and therefore the diversification of the rhodopsin-like GPCR family began at least 700 million years ago, prior to the divergence of cnidarians and bilaterians. ORs and other rhodopsin-like GPCRs have roles in cell migration, axon guidance, and neurite growth; therefore, duplication and divergence in this family may have played a key role in the evolution of cell type diversity (including the emergence of complex nervous systems) and in the evolution of metazoan body plan diversity.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".