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12th International Symposium on Bioluminescence & Chemiluminescence |
Symposium abstracts:
William W. Ward
Rutgers University, Cook College, 76 Lipman Drive, New Brunswick, N.J.
08901, USA
Email: crebb@rci.rutgers.edu
A major obstacle in doing creative scientific research is the need to rely upon pre-conceived notions--ones that later prove to be false. Sometimes these notions have been published, sometimes they are widely accepted, sometimes they are codified in textbooks and taught in classrooms for years--even decades, and sometimes they are one's own notions. In my 30 years of research on the green-fluorescent protein, I have been led astray by many false notions, some of my own creation: the quantum yield is 30%, protein renaturation must be done very, very slowly, GFP is so stable that it can be stored safely for years at 4°C, and any attempts to clone GFP would be a waste of time as it would only produce the non-fluorescent apoprotein. A current notion under scrutiny is the ecological function of fluorescent proteins in cnidaria. We assumed for decades, essentially without proof, that the sole function for GFP is to alter the emission wavelength and improve the quantum yield of bioluminescence. Then along came Mikhail Matz who showed that non-bioluminescent corals and sea anemones have fluorescent proteins genetically homologous to those of bioluminescent jellyfish and sea pansies. So much for the old notion. O.K., so where does this leave us? Sunscreens? I doubt it. Photosynthesis boosters? Not likely. My notion, and it is still just a notion, is that fluorescent proteins are produced in corals and sea anemones for visual contrast. These organisms must have a need to be seen. Bright pigments play major roles in terrestrial ecology, but, several meters below sea level, all pigments take on various shades of blue. Regardless of pigmentation, there is no color contrast when all the downwelling light is blue. So, organisms that wish to be seen against the blue background must absorb blue light and then emit green, yellow, or red fluorescence. We might wish to call this phenomenon "fluorescence advertising." So, it is now my notion that coelenterate fluorescent proteins first evolved for color contrast and fluorescence advertising. Later, when some of these organisms became bioluminescent, their fluorescent proteins evolved to play their now familiar roles in bioluminescence energy transfer. Taking yet a further leap, I wonder if homologues of the green-fluorescent protein are restricted to the Phylum Cnidaria. Perhaps "advertising" with homologous fluorescent proteins cuts across phylogenetic boundaries.
This
is a preprint of an article accepted for publication in Luminescence: Copyright
2001 John
Wiley & Sons, Ltd (Wiley website)