The association between MC1R mutation and amphibian pigment adaptation is revealed for the first time.

Cave adaptation is an extreme and interesting biological phenomenon.
in amphibians, the red-dot redostigmatus are well adapted to cave life, and their skin is transparent in caves where karst landscapes are long-term;
at the same time, the slugs exposed to natural light change from transparent to gray-black at 15 years old.
suggests that its pigment system is particularly important, both to ensure very low pigment distribution under lightless conditions, but also to ensure rapid skin pigment cover under light to resist UV rays.
in response to this phenomenon, Zhu Wei, Wang Bin and others of Jiang Jianping Research Team of Chengdu Institute of Biological Sciences of the Chinese Academy of Sciences compared the gene expression changes of red dot teeth after exposure to different light times, and found that the essence of red dot tooth-and-tooth skin blackification under the light was the proliferation of melanin cells and the starting synthesis of melanin (morphological color changes), rather than pigmentation and aggregation within cell dispersion (physiological color change).
generally speaking, morphological color changes occur much more slowly than physiological color changes (hours), often taking days to weeks to observe significant changes.
So how do red-dot-toothed slugs achieve rapid morphological color changes? The analysis shows that light activates strong cell proliferation and division signals, including PDGF, FGF, HGF and other growth factor signals and their downstream MAPK signals and PI3K-Akt signals, which provides the basis for rapid morphological change.
study also found that there were four fragments of amino acids in the outer region between the second transmembrane helix of the M1CR gene (melanoblasts stimulate hormone receptors) of the red dot tooth herring, which is located in the MC1R ligand binding region.
MC1R is a key receptor for the proliferation and pigmentsynthesis of melanocytes, and its ligand is positively charged alpha-MSH (melanocyte stimulation hormone), which is released by ultraviolet stimulation.
protein 3D reconstruction shows that the deletion of the fragment leads to the extension of the third trans membrane spiral of the red-dot toothed tooth, and at the same time makes the three Asp residuals (only 1 other frog) in series arranged in the ligand pocket, forming a negatively charged trap-like structure, thus enhancing the response to the MSH signal and achieving rapid blacking. In addition,
the study confirmed that the positive charge level of the MC1R ligand binding domain was positively related to its background activity, and that many blackening phenomena, such as blackened jaguars, blacked-out mice, black foxes, etc., were associated with the alkalinization or deacidification mutations in the region.
the ligand binding domain of the red-dot toothed MC1R has three Asp negative charges, which can be inferred as having a lower background activity, and also provideans for transparent phenotypes in cave environments.
therefore, the fragment loss of MC1R and the mutation of amino acids are the key to adapt ingestion to the cave environment in pigmentation.
the study reveals for the first time the association between MC1R mutations and amphibian pigment adaptation, and provides a new perspective on the color adaptation mechanisms of non-specialized cave species.
related research published in BMC Genomics.
the research was funded by the Chinese Academy of Sciences' key deployment project, the National Natural Science Foundation of China and the "Western Light" project.
.