FIP IN-PERSON Seminar for Honorable Mention Postdoc Speaker Award "Hidden in the forest: from camouflage to novel fluorescent proteins and mechanisms of transparency in neotropical treefrogs"
Hundreds of neotropical frogs evolved biochemical tricks for signaling and camouflage involving strong fluorescence, novel colored proteins, and remarkable mechanisms that maintain the transparency of their tissues. In particular, green treefrogs co-opted a group of serpin proteins -with ancient immunological and blood coagulation functions- that bind biliverdin and make the animals leaf-like green, matching the reflectance of the canopy to the tiniest details. These serpins (Biliverdin-binding serpins, or BBSs) constitute a novel group of near-infrared (NIR) fluorescent proteins that evolved more than 40 times, offering an unparalleled opportunity to rationalize the biochemical bases of their spectral diversity, as well as a powerful toolbox of fluorescent proteins for deep-tissues imaging in vivo.
Among treefrogs expressing BBSs, dozens of species -known as glassfrogs- are the only examples of transparent terrestrial vertebrates. Their optical clarity parallels that of the most transparent zebrafish models, revealing their internal anatomy, circulatory and lymphatic systems. Here we show some of the mechanisms that make glassfrogs transparent and allow them to hide in the canopy. Using a combination of ultrasound and photoacoustic imaging, as well as a set of spectroscopic techniques, we document for the first time that glassfrogs evolved novel cardiovascular strategies that make them transparent, while at the same make them resistant to common blood disorders such as vein thrombosis. We also show how their BBSs proteins are responsible for their green hue, and we describe some applications in fluorescence and photoacoustic imaging in vivo.
Taken together, the study of non-model frog systems with a complex biochemical evolution and remarkable physiological traits offers a great opportunity for bioinspired research.