 |
| Coelacanth, Latimeria chalumnae. Graphic: Sabine Bijewitz, Template Drawing: Robbie Cada. |
Creationist dupes are constantly attacking what they like to pretend are problems with the fossil record, imagining that the entire Theory of Evolution depends on fossils and fossils alone.
It doesn't, of course and the TOE would still stand up to scrutiny even if we had never found a fossil. The geological/paleontological evidence of fossils is merely additional supporting evidence to the mass of evidence to be found in the biochemical, physiological, genetic and anatomical record, all of which show evidence of common origins and the nested hierarchies this predicts.
Now a team of researchers from Technical University of Munich Leibniz-Institute for Food Systems Biology have revealed even more evidence of common origins in the form of taste receptors in fish that perform the same function in humans. The team compared two original bitter receptor types from the coelacanth (Latimeria chalumnae) with four others from the zebrafish (Danio rerio) phylogenetically, functionally and structurally.
They found that they were essentially identical in both species even though they were separated by 400 million years of evolution. What's more, the test system they used showed that these fish taste receptors recognise the same bitter substances as do humans!
At first sight this might look like there has been no evolution over that period, however, as the researchers point out, this is evidence that the ability to taste bitter things is so important, especially to carnivores, that it is highly conserved during evolution.
 |  |
| Coelacanth, Latimeria chalumnae | Zebrafish, Danio rerio |
Both species have essentially the same bitter-taste receptors, although separated by 400 million years of evolution. | |
Evolutionarily, bitter receptors are a relatively recent invention of nature compared to other chemoreceptors, such as olfactory receptors. Their function of protecting vertebrates from consuming potentially toxic substances has long been scientifically recognized. More recent are observations that bitter receptors have other functions beyond taste perception. These include roles in defense against pathogenic bacteria, in metabolic regulation, and possibly also functions as sensors for endogenous metabolites and hormones.The team's research was published open access just before Christmas, 2020 in the Oxford University Press journal, Genome Biology and Evolution:
Coelacanth and zebrafish in comparison
The team of scientists led by biologists Sigrun Korsching of the University of Cologne and Maik Behrens of the Leibniz Institute for Food Systems Biology now provides further evidence to support this hypothesis. In their current study, the team compared two original bitter receptor types from the coelacanth (Latimeria chalumnae) with four others from the zebrafish (Danio rerio) phylogenetically, functionally and structurally. To this end, the research team conducted, among other experiments, extensive functional studies using an established cell-based test system as well as a computer-based modeling approach. The goal was to gain a deep insight into the evolutionary history of bitter receptors in order to learn more about their functions.
As the study results show, both fish species possess, amongst others, a pair of homologous bitter receptor genes that presumably arose from a primordial gene. In this regard, the bitter recognition spectra of these fish receptors were largely identical despite 400 million years of separate evolution, according to the results of the functional studies. "What is particularly exciting about our results is that the original fish receptors recognized substances in the cellular test system which are still detected by human bitter receptors to date. These include bile acids," says co-author Antonella Di Pizio of the Leibniz Institute.
Over 400 million years of selection pressure
"So there must have been selective pressure at least until humans evolved, that means human bitter receptors can still detect the same bitter substances as a bony fish did over 400 million years ago," concludes taste researcher Maik Behrens. Sigrun Korsching adds, "This speaks for one or more important functions of bitter receptors, even during human evolution."
"Coelacanths are carnivores. Therefore, one could speculate that the existence of a bitter receptor variant that mainly recognizes steroid hormones and bile acids protects against the consumption of poisonous fish, which can contain not only bile acids but also highly potent neurotoxins in their liver and gallbladder. For example, the poisonous puffer fish Arothron hispidus lives in the same waters as the coelacanth," says Maik Behrens. "In humans and also in zebrafish, however, it is questionable whether such a receptor variant would have been preserved from an evolutionary point of view if it did not have other functions inside the body. Another argument in favor of such extraoral functions is that bitter receptors are also found on human organs such as the heart, brain or thyroid gland," Behrens added. One goal of his research is to help understand the effects of bitter substances on a systems biological level, regardless of whether they entered the body through food or whether they belong to the body's own substances.
As an incidental aside, I wonder how many Creationists can spot any evidence in this paper that the TOE is a theory in crisis, and about to become the first ever example of a scientific theory being replaced by a belief in supernatural magic, like intelligent [sic] design creationists keep assuring the word. It looks for all the world as though this research team, like all the other research biologist producing serious research papers, haven't heard that news yet and still believe the TOE is the theory underpinning all of biology.Abstract
The careful evaluation of food is important for survival throughout the animal kingdom, and specialized chemoreceptors have evolved to recognize nutrients, minerals, acids, and many toxins. Vertebrate bitter taste, mediated by the taste receptor type 2 (T2R) family, warns against potentially toxic compounds. During evolution T2R receptors appear first in bony fish, but the functional properties of bony fish T2R receptors are mostly unknown. We performed a phylogenetic analysis showing the “living fossil” coelacanth (Latimeria chalumnae) and zebrafish (Danio rerio) to possess T2R repertoires typical for early-diverged species in the lobe-finned and the ray-finned clade, respectively. Receptors from these two species were selected for heterologous expression assays using a diverse panel of bitter substances. Remarkably, the ligand profile of the most basal coelacanth receptor, T2R01, is identical to that of its ortholog in zebrafish, consistent with functional conservation across >400 Myr of separate evolution. The second coelacanth receptor deorphaned, T2R02, is activated by steroid hormones and bile acids, evolutionary old molecules that are potentially endogenously synthesized agonists for extraoral T2Rs. For zebrafish, we report the presence of both specialized and promiscuous T2R receptors. Moreover, we identified an antagonist for one of the zebrafish receptors suggesting that bitter antagonism contributed to shape this receptor family throughout evolution.
Di Pizio, Antonella; Redel, Ulrike; Meyerhof, Wolfgang; Korsching, Sigrun I
At the Root of T2R Gene Evolution: Recognition Profiles of Coelacanth and Zebrafish Bitter Receptors
Genome Biology and Evolution, Volume 13, Issue 1, January 2021, evaa264, doi: 10.1093/gbe/evaa264
Copyright: © 2021 The authors. Published by Oxford University Press
on behalf of the Society for Molecular Biology and Evolution.
Open access
Reprinted under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0)
No comments :
Post a Comment
Obscene, threatening or obnoxious messages, preaching, abuse and spam will be removed, as will anything by known Internet trolls and stalkers, by known sock-puppet accounts and anything not connected with the post,
A claim made without evidence can be dismissed without evidence. Remember: your opinion is not an established fact unless corroborated.