The <i>Drosophila tyramine-beta-hydroxylase</i> gene encodes multiple isoforms with different functions
Bibliographic record
Abstract
Abstract The Tyramine-beta−hydroxylase (Tbh) is required for octopamine synthesis. To better understand the function of Tbh in neurotransmitter synthesis, we analyzed the molecular genetic organization of the Drosophila melanogaster Tbh gene and found that the Tbh gene encodes multiple transcripts. The transcripts differ in their 5’UTR, which results in proteins that differ in their size and putative phosphorylation sites, suggesting that the Tbh function is regulated at translational and posttranslational levels. We generated a new Tbh mutant – Tbh Del3 - using FLP/FRT recombination mutagenesis to remove the translational start site still that is present in Tbh nM18 mutants. The Tbh Del3 mutants share ethanol tolerance and larval locomotion defects with the Tbh nM18 mutants. But, they differ in terms of their cellular stress response. To develop normal levels of ethanol tolerance, Tbh is required in a subset of Tbh expressing neurons in the adult brain, which was identified using a newly generated Tbh -Gal4 driver. Taking advantage of a newly generated Tbh antibody serum, we show that one Tbh isoform is expressed in a group of peptidergic Hugin-positive and noradrenergic neurons uncoupling Tbh function from octopamine synthesis. The existence of different functional Tbh isoforms impacts our understanding of the regulatory mechanisms of neurotransmitter synthesis and the function of the octopaminergic neurotransmitter system in cellular processes and the regulation of behavior. Author Summary Vertebrates and insects have structurally identical signaling molecules in their nervous system, such as the neurotransmitter dopamine. But, there are also neurotransmitters that are thought to only occur in the vertebrate or insect brain. Noradrenaline is one such neurotransmitter that regulates flight and fight responses in vertebrates. In insects such as the fruit fly Drosophila melanogaster , the structurally very similar neurotransmitter octopamine is considered to be an invertebrate-specific neurotransmitter that performs similar functions to noradrenaline. The functional similarities also extend to enzymes required for synthesis. Our analysis shows that the enzyme for octopamine synthesis exists in several variations and that the connection between the enzymes and the synthesized neurotransmitter may not be as simple as presumed. Exploiting molecular, behavioral and neuroanatomical studies, we show that different variants might be used in response to different environmental conditions and/or the synthesis of alternative, structurally similar neurotransmitters, such as noradrenaline. These results challenge our view on the functions of octopamine and noradrenaline in the regulation of behavior.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".