Biofluorescence

Biofluorescence is frequent in plants, and can occur in many of their parts.{{Cite journal |last=Holovachov |first=Oleksandr |date=2015-09-02 |title=Unseen beauty of flowers – hidden signals or spectacular by-product? |url=http://www.tandfonline.com/doi/full/10.1080/14688417.2015.1078121 |journal=Green Letters |volume=19 |issue=3 |pages=329–331 |doi=10.1080/14688417.2015.1078121 |issn=1468-8417}} The biofluorescence in chlorophyll but has been studied since the 1800s.{{Cite journal |last1=Lagorio |first1=M. Gabriela |last2=Cordon |first2=Gabriela B. |last3=Iriel |first3=Analia |date=September 2015 |title=Reviewing the relevance of fluorescence in biological systems |url=https://link.springer.com/10.1039/c5pp00122f |journal=Photochemical & Photobiological Sciences |language=en |volume=14 |issue=9 |pages=1538–1559 |doi=10.1039/c5pp00122f |issn=1474-905X|hdl=11336/8072 |hdl-access=free }} Generally, chlorophyll fluoresces red,{{Cite journal |last1=Murchie |first1=E.H. |last2=Lawson |first2=T. |date=October 2013 |title=Chlorophyll fluorescence analysis: a guide to good practice and understanding some new applications |url=https://academic.oup.com/jxb/article-lookup/doi/10.1093/jxb/ert208 |journal=Journal of Experimental Botany |volume=64 |issue=13 |pages=3983–3998 |doi=10.1093/jxb/ert208 |pmid=23913954 |issn=1460-2431}} and can be used as a measure of photosynthetic capabilities,{{Cite journal |last1=Krause |first1=G. Heinrich |last2=Weis |first2=Engelbert |date=1984 |title=Chlorophyll fluorescence as a tool in plant physiology: II. Interpretation of fluorescence signals |url=http://link.springer.com/10.1007/BF00028527 |journal=Photosynthesis Research |language=en |volume=5 |issue=2 |pages=139–157 |doi=10.1007/BF00028527 |pmid=24458602 |issn=0166-8595|url-access=subscription }} or general health. After absorbing light, chlorophyll may fluoresce as part of the physiological processes involved in photosynthesis.

Reproductive organs such as pollen,{{Cite journal |last=Roshchina |first=Victoria V. |date=2012-09-10 |title=Vital Autofluorescence: Application to the Study of Plant Living Cells |journal=International Journal of Spectroscopy |volume=2012 |pages=1–14 |doi=10.1155/2012/124672 |doi-access=free |issn=1687-9449}}{{Cite journal |last1=Mori |first1=Shinnosuke |last2=Fukui |first2=Hiroshi |last3=Oishi |first3=Masanori |last4=Sakuma |first4=Masayuki |last5=Kawakami |first5=Mari |last6=Tsukioka |first6=Junko |last7=Goto |first7=Katsumi |last8=Hirai |first8=Nobuhiro |date=2018-06-01 |title=Biocommunication between Plants and Pollinating Insects through Fluorescence of Pollen and Anthers |url=https://doi.org/10.1007/s10886-018-0958-9 |journal=Journal of Chemical Ecology |volume=44 |issue=6 |pages=591–600 |doi=10.1007/s10886-018-0958-9 |pmid=29717395 |bibcode=2018JCEco..44..591M |issn=1573-1561|url-access=subscription }} anthers or petals{{Cite journal |last1=Gandía-Herrero |first1=Fernando |last2=García-Carmona |first2=Francisco |last3=Escribano |first3=Josefa |date=September 2005 |title=Floral fluorescence effect |url=https://www.nature.com/articles/437334a |journal=Nature |language=en |volume=437 |issue=7057 |pages=334 |doi=10.1038/437334a |pmid=16163341 |issn=0028-0836}} may also fluoresce. These characters may produce a variety of colors depending on the pigment responsible for fluorescence. While it is unclear what the primary function of different kinds of fluorescence are in plants, reproductive characters may biofluoresce as a signal to attract pollinators,{{Cite journal |last=Gumbert |first=A. |date=2000-06-01 |title=Color choices by bumble bees (Bombus terrestris): innate preferences and generalization after learning |url=https://doi.org/10.1007/s002650000213 |journal=Behavioral Ecology and Sociobiology |language=en |volume=48 |issue=1 |pages=36–43 |doi=10.1007/s002650000213 |issn=1432-0762|url-access=subscription }} However, biofluorescence may also attract prey in predatory plants,{{Cite journal |last1=Kurup |first1=R. |last2=Johnson |first2=A. J. |last3=Sankar |first3=S. |last4=Hussain |first4=A. A. |last5=Kumar |first5=C. Sathish |last6=Sabulal |first6=B. |date=May 2013 |editor-last=Rennenberg |editor-first=H. |title=Fluorescent prey traps in carnivorous plants |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1438-8677.2012.00709.x |journal=Plant Biology |volume=15 |issue=3 |pages=611–615 |doi=10.1111/j.1438-8677.2012.00709.x |pmid=23696970 |bibcode=2013PlBio..15..611K |issn=1435-8603|url-access=subscription }} or serve no function.

While biofluorescence was first discovered and extensively characterized in invertebrates, recent work has observed biofluorescence in many vertebrates, with discoveries of biofluorescence have been made in salamanders and frogs,{{Cite journal |last1=Lamb |first1=Jennifer Y. |last2=Davis |first2=Matthew P. |date=2020-02-27 |title=Salamanders and other amphibians are aglow with biofluorescence |journal=Scientific Reports |language=en |volume=10 |issue=1 |page=2821 |doi=10.1038/s41598-020-59528-9 |issn=2045-2322 |pmc=7046780 |pmid=32108141|bibcode=2020NatSR..10.2821L }}{{Cite journal |last1=Santa-Cruz |first1=Roy |last2=von May |first2=Rudolf |last3=Catenazzi |first3=Alessandro |last4=Whitcher |first4=Courtney |last5=López Tejeda |first5=Evaristo |last6=Rabosky |first6=Daniel |date=2019-08-26 |title=A New Species of Terrestrial-Breeding Frog (Amphibia, Strabomantidae, Noblella) from the Upper Madre De Dios Watershed, Amazonian Andes and Lowlands of Southern Peru |journal=Diversity |language=en |volume=11 |issue=9 |pages=145 |doi=10.3390/d11090145 |doi-access=free |issn=1424-2818}}{{Cite journal |last1=Whitcher |first1=Courtney |last2=Beaver |first2=Lilyanne |last3=Lemmon |first3=Emily Moriarty |date=February 2024 |title=The effect of biofluorescence on predation upon Cope's gray treefrog: A clay model experiment |url=https://linkinghub.elsevier.com/retrieve/pii/S0376635724000111 |journal=Behavioural Processes |language=en |volume=215 |pages=104996 |doi=10.1016/j.beproc.2024.104996|url-access=subscription }} fish, birds,{{Cite journal |last1=Pearn |first1=Sophie M. |last2=Bennett |first2=Andrew T.D. |last3=Cuthill |first3=Innes C. |date=2001-11-07 |title=Ultraviolet vision, fluorescence and mate choice in a parrot, the budgerigar Melopsittacus undulatus |journal=Proceedings of the Royal Society of London. Series B: Biological Sciences |language=en |volume=268 |issue=1482 |pages=2273–2279 |doi=10.1098/rspb.2001.1813 |issn=0962-8452 |pmc=1088876 |pmid=11674876}}{{Cite journal |last1=Hausmann |first1=Franziska |last2=Arnold |first2=Kathryn E. |last3=Marshall |first3=N. Justin |last4=Owens |first4=Ian P. F. |date=2003-01-07 |title=Ultraviolet signals in birds are special |journal=Proceedings of the Royal Society of London. Series B: Biological Sciences |language=en |volume=270 |issue=1510 |pages=61–67 |doi=10.1098/rspb.2002.2200 |issn=0962-8452 |pmc=1691211 |pmid=12590772}}{{Cite report |url=https://figshare.utas.edu.au/articles/journal_contribution/Update_on_fluorescent_mammals_and_birds_in_Tasmania/25131257/1 |title=Update on fluorescent mammals and birds in Tasmania |last=Gershwin |first=Lisa-ann |date=2024-02-05 |doi=10.26749/25131257.v1}} and mammals.{{Cite journal |last1=Anich |first1=Paula Spaeth |last2=Anthony |first2=Sharon |last3=Carlson |first3=Michaela |last4=Gunnelson |first4=Adam |last5=Kohler |first5=Allison M. |last6=Martin |first6=Jonathan G. |last7=Olson |first7=Erik R. |date=2021-03-26 |title=Biofluorescence in the platypus ( Ornithorhynchus anatinus ) |url=https://www.degruyter.com/document/doi/10.1515/mammalia-2020-0027/html |journal=Mammalia |language=en |volume=85 |issue=2 |pages=179–181 |doi=10.1515/mammalia-2020-0027 |issn=1864-1547}}{{Cite journal |last1=Olson |first1=Erik R. |last2=Carlson |first2=Michaela R. |last3=Ramanujam |first3=V. M. Sadagopa |last4=Sears |first4=Lindsay |last5=Anthony |first5=Sharon E. |last6=Anich |first6=Paula Spaeth |last7=Ramon |first7=Leigh |last8=Hulstrand |first8=Alissa |last9=Jurewicz |first9=Michaela |last10=Gunnelson |first10=Adam S. |last11=Kohler |first11=Allison M. |last12=Martin |first12=Jonathan G. |date=2021-02-18 |title=Vivid biofluorescence discovered in the nocturnal Springhare (Pedetidae) |journal=Scientific Reports |language=en |volume=11 |issue=1 |page=4125 |doi=10.1038/s41598-021-83588-0 |issn=2045-2322 |pmc=7892538 |pmid=33603032|bibcode=2021NatSR..11.4125O }}

The function of biofluorescence in each case is not completely known. The fluorescent signal may play a role in inter- and intraspecific communication, such as camouflage (e.g. corals{{Cite journal |last1=Matz |first1=Mikhail V. |last2=Marshall |first2=N. Justin |last3=Vorobyev |first3=Misha |date=2006 |title=Are Corals Colorful? |url=https://onlinelibrary.wiley.com/doi/10.1562/2005-08-18-RA-653 |journal=Photochemistry and Photobiology |language=en |volume=82 |issue=2 |pages=345–350 |doi=10.1562/2005-08-18-RA-653 |pmid=16613484 |issn=0031-8655|url-access=subscription }}), attracting mates (e.g. birds{{Cite journal |last1=Hausmann |first1=Franziska |last2=Arnold |first2=Kathryn E. |last3=Marshall |first3=N. Justin |last4=Owens |first4=Ian P. F. |date=2003 |title=Ultraviolet signals in birds are special |journal=Proceedings of the Royal Society of London. Series B: Biological Sciences |volume=270 |issue=1510 |pages=61–67 |doi=10.1098/rspb.2002.2200 |issn=0962-8452 |pmc=1691211 |pmid=12590772}} and copepods{{Cite journal |last1=Shagin |first1=Dmitry A. |last2=Barsova |first2=Ekaterina V. |last3=Yanushevich |first3=Yurii G. |last4=Fradkov |first4=Arkady F. |last5=Lukyanov |first5=Konstantin A. |last6=Labas |first6=Yulii A. |last7=Semenova |first7=Tatiana N. |last8=Ugalde |first8=Juan A. |last9=Meyers |first9=Ann |last10=Nunez |first10=Jose M. |last11=Widder |first11=Edith A. |last12=Lukyanov |first12=Sergey A. |last13=Matz |first13=Mikhail V. |display-authors=6 |date=2004 |title=GFP-like Proteins as Ubiquitous Metazoan Superfamily: Evolution of Functional Features and Structural Complexity |url=https://academic.oup.com/mbe/article-lookup/doi/10.1093/molbev/msh079 |journal=Molecular Biology and Evolution |volume=21 |issue=5 |pages=841–850 |doi=10.1093/molbev/msh079 |pmid=14963095 |issn=1537-1719|url-access=subscription }}) and symbionts (e.g. corals), or deterring predators.

Other explanations are physiological, with bright color being a side-product of a defense from UV (e.g. the protein sandercyanin, and UV protection of genes in pollen). Bright red fluorescence in the larvae of Acropora millepora coral correlates with the activation of a diapause-like state that may aid in conserving energy and tolerating heat and other stressors during a long dispersal to novel habitats.{{Cite journal |last1=Strader |first1=Marie E. |last2=Aglyamova |first2=Galina V. |last3=Matz |first3=Mikhail V. |date=January 2016 |title=Red fluorescence in coral larvae is associated with a diapause-like state |url=https://onlinelibrary.wiley.com/doi/10.1111/mec.13488 |journal=Molecular Ecology |language=en |volume=25 |issue=2 |pages=559–569 |doi=10.1111/mec.13488 |pmid=26600127 |bibcode=2016MolEc..25..559S |issn=0962-1083|url-access=subscription }}

Most likely biofluorescence arose multiple times by convergent evolution.{{Cite journal |last1=Ugalde |first1=Juan A. |last2=Chang |first2=Belinda S. W. |last3=Matz |first3=Mikhail V. |date=2004-09-03 |title=Evolution of Coral Pigments Recreated |url=https://www.science.org/doi/10.1126/science.1099597 |journal=Science |volume=305 |issue=5689 |pages=1433 |doi=10.1126/science.1099597 |pmid=15353795 |issn=0036-8075|url-access=subscription }} Reconstruction experiments suggest the original fluorescent protein was green, and had a simple beta-barrel shape with a chromophore hidden inside. Different colors of green fluorescent proteins (GFP), yellow, red, cyan, and amber, are determined by variations in chromophore structure. Red fluorescent proteins chromophore are the most complex and require extra maturation steps. New fluorescent proteins evolved through gene duplication and accumulation of multiple mutations which gradually changed autocatalytic functions and final chromophore structure.

GFP analogs are common, but this is not the only possible structural solution for biofluorescence. In freshwater Japanese eels Anguilla japonica the unique protein UnaG fluoresces by binding bilirubin, a mechanism very distinct from that of green fluorescent protein.{{Cite journal |last1=Kumagai |first1=Akiko |last2=Ando |first2=Ryoko |last3=Miyatake |first3=Hideyuki |last4=Greimel |first4=Peter |last5=Kobayashi |first5=Toshihide |last6=Hirabayashi |first6=Yoshio |last7=Shimogori |first7=Tomomi |last8=Miyawaki |first8=Atsushi |display-authors=6 |date=June 2013 |title=A Bilirubin-Inducible Fluorescent Protein from Eel Muscle |url=https://linkinghub.elsevier.com/retrieve/pii/S0092867413006442 |journal=Cell |volume=153 |issue=7 |pages=1602–1611 |doi=10.1016/j.cell.2013.05.038|pmid=23768684 |doi-access=free }} UnaG absorbs blue light and emits green only when the complex with bilirubin is formed. This feature makes UnaG attractive for biomedical assays in exploration of bilirubin-dependent cellular processes.{{Cite journal |last1=Yeh |first1=Johannes T.-H. |last2=Nam |first2=Kwangho |last3=Yeh |first3=Joshua T.-H. |last4=Perrimon |first4=Norbert |date=2017-02-08 |title=eUnaG: a new ligand-inducible fluorescent reporter to detect drug transporter activity in live cells |journal=Scientific Reports |volume=7 |issue=1 |page=41619 |doi=10.1038/srep41619 |issn=2045-2322 |pmc=5296874 |pmid=28176814|bibcode=2017NatSR...741619Y }}

Another non-GFP- like fluorescent protein is a blue protein, sandercyanin, from freshwater fish walleye, Sander vitreus, in the North hemisphere. Sandercyanin is seasonally produced, with production peaking in the late summer, and is thought to be a defense against high UV. Sandercyanin binds biliverdin IXa, and together they form a tetra-homomer which absorbs UV light at 375nm and emits red light at 675nm.{{Cite journal |last1=Ghosh |first1=Swagatha |last2=Yu |first2=Chi-Li |last3=Ferraro |first3=Daniel J. |last4=Sudha |first4=Sai |last5=Pal |first5=Samir Kumar |last6=Schaefer |first6=Wayne F. |last7=Gibson |first7=David T. |last8=Ramaswamy |first8=S. |display-authors=6 |date=2016-10-11 |title=Blue protein with red fluorescence |journal=Proceedings of the National Academy of Sciences |volume=113 |issue=41 |pages=11513–11518 |doi=10.1073/pnas.1525622113 |doi-access=free |issn=0027-8424 |pmc=5068307 |pmid=27688756|bibcode=2016PNAS..11311513G }}

Two species of catsharks, Cephaloscyllium ventriosum, endemic to the eastern Pacific, and Scyliorhinus retifer, from the western Atlantic, fluoresce by a different mechanism.{{Cite journal |last1=Park |first1=Hyun Bong |last2=Lam |first2=Yick Chong |last3=Gaffney |first3=Jean P. |last4=Weaver |first4=James C. |last5=Krivoshik |first5=Sara Rose |last6=Hamchand |first6=Randy |last7=Pieribone |first7=Vincent |last8=Gruber |first8=David F. |last9=Crawford |first9=Jason M. |display-authors=6 |date=September 2019 |title=Bright Green Biofluorescence in Sharks Derives from Bromo-Kynurenine Metabolism |journal=iScience |volume=19 |pages=1291–1336 |doi=10.1016/j.isci.2019.07.019 |pmc=6831821 |pmid=31402257|bibcode=2019iSci...19.1291P }} The fluorescence is produced by brominated tryptophan-kynurenine metabolites, small aromatic compounds present in the lighter-colored regions of skin on the fish. Dermal features of the shark skin optically enhance the fluorescent signal.

• Bioluminescence

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Category:Biofluorescence