Vision in the Ultraviolet
SLU Biology Departmental seminar
September 9, 2004
It has been 3 years since my last Biology seminar.
Spectrum. The "visible" spectrum can be seen inside my grating monochromator.
Drosophila. (Stark and Thomas 2004 Full paper on line.)
Abstract #1. Electrophysiology and genetic dissection demonstrated that R7, one receptor type in the compound eye, is a UV receptor. Behavioral analyses showed that it dominates in phototaxis; hence flies are attracted to UV. R1-6, the predominant compound eye receptor type, has a blue-absorbing rhodopsin and is sensitized to UV by a retinoid.
Receptors and rhodopsins: R1-6 (Rh1), ocelli (Rh2), R7 (Rh3 and Rh4), and R8 (Rh5 and Rh6)
Distal ommatidium (EM) -- R1-6 & R7
Mutants like sevenless (sev) were used in a genetic dissection of vision and to show that R7 is a UV receptor (Harris, Stark and Walker, 1976).
coworkers William A Harris, Karin G. Hu, Gregory V. Miller and Karen N. Hansen
Using either electrophysiology or behavior and mutants or chromatic adaptation, 3 spectra were isolated from the Drosophila eye.
Further information - Genetic dissection, Phototaxis
R1-6's R-480 (Rh1) is sensitized to UV by
coworker Robert Greenberg
The UV peak is preferentially decreased with vitamin A deprivation.
There is a vitamin A dependent autofluorescence from R1-6
Confocal micrograph of above (Stark and Thomas, 2004)
UV phototactic behavior
(phototaxis then and now, Michael Haskins, Spring 2005)
Abstract #2. R1-6 degenerate in a retinal degeneration mutant, rdgB, but it still has phototaxis mediated by R7. Mutants of R1-6's rhodopsin lack phototaxis even though R7 survives and functions.
Despite R1-6 damage in rdgB (Stark and Carlson, 1982), R7/8 survive and mediate phototaxis (Harris, Stark and Walker, 1976; Hu & Stark, 1976)
ninaE (ora) (Stark and Sapp, 1987), an Rh1 mutant, is tidier but lacks phototaxis (Harris, Stark and Walker, 1976; Hu & Stark, 1976)
rdgB is like w but ninaE lacks phototaxis.
Two types of R7
coworkers Charles F. Thomas and De-Mao Chen
Abstract #3. Since my work showing R7 is a UV receptor, several labs showed there are two types of R7 with different rhodopsins, confirmed with electrophysiology and confocal microscopy.
Electrophysiology (Methods - transgenics with Rh3 and Rh4 replacing Rh1 in R1-6)
Confocal images (autofluorescence) from housefly and fruitfly (Stark and Thomas, 2004).
GFP labels those cells containing Rh4 (Stark and Thomas, 2004).
sponsor DSM (formerly Roche)
Abstract #4. One of my laboratory's findings is that vitamin A not only serves as the precursor for rhodopsin's chromophore but also activates transcription. Since zeaxanthin and lutein are precursors of the 3-hydroxylated chromophore used in insects, I tested these compounds in transcriptional studies on the UV receptors using green fluorescent protein (GFP)
by lutein and zeaxanthin
UV light damage
coworker Stanley D. Carlson
Abstract #5. Very intense UV light is damaging to Drosophila receptors, and vitamin A deprivation shows that the damage is mediated through rhodopsin.
Putting a white Drosophila eye in a fluorescence microscope.
Calibration of light intensity is very important in my research. Clockwise from noon: Photomultiplier and power supply, thermopile, radiometer/photometer, and photodiode with batteries (used most often).
UV damage (in R1-6, but not R8): High Voltage Electron Micrograph (HVEM) of proximal ommatidium of white-eyed Drosophila 1 week after UV at 19.38 log quanta per square cm; vitamin A deprivation showed that the damage was mediated through light absorption by rhodopsin (Stark and Carlson, 1984)
coworkers De-Mao Chen, Russell F. Mizell III, Wendy Mechaber, Guangjun Dong, Stanley D. Carlson.
Abstract #6. My lab was in a position to assist several collaborators who were interested in spectral sensitivity in the insects they studied.
Defunct dogma that vertebrates do not see
Abstract #7. Soon after my 1982 review on UV vision, fish and birds were shown to have UV sensitivity, then other vertebrates including mice.
Birds, work by Goldsmith & Chen.
coworkers De-Mao Chen & Guangjun Dong
Abstract #8. Fish have very interesting visual systems, noted for good organization of receptors (retinal mosaic) and continuous development akin to the Drosophila imaginal disk. Juvenile goldfish have UV sensitivity mediated by UV cones but lose that sensitivity as they age. Moderate UV light damages cones, but not the UV cones; further, the damage seems to be in mitochondria primarily.
The mosaic of a juvenile goldfish shows Double cones (D), Long single cones (Lc), Short single cones (Sc), and ultraviolet cones (uv).
Spectral sensitivity of Juvenile and adult goldfish (from Chen and Stark, 1994).
A UV cone survives [with normal mitochondria (M)]12 days of light exposure surrounded by damaged double cones with displaced mitochondria (middle of figure). Rods survive (upper right)..
coworkers De-Mao Chen, Martin L. Katz and Gregory I Liou
Abstract #9. While pursuing other issues, we found that the UV sensitivity mice were known to posess is prefernetially decreased by vitamin A deprivation.
In this demonstration of vitamin A mediated recovery of sensitivity in deprived mice, it is also clear that deprivation preferentially affects the UV cones (Liou et al.)..1988, Full paper on-line.
Abstract #10. Aphacic subjects
can see UV, and I had cataract surgery at age 10.
Lens. of 79 and 39 yr old looks yellow and absorbs most of the UV light.
Rod (scotopic) data indicates that UV sensitivity is increased 4 orders of magnitude after cataract surgery.
Demonstration - what UV looks like (a whitish blue)
I explained this with data showing that all 3 cone types have UV sensitivity, especially the blue cone, but I prefer Tan's psychometric data (with an artists "color circle").
Lillies at Giverney look bluer after Monet's
This work attracts attention, e.g. science feature by Hambling.
Abstract #11. It was complicated but possible to shoot pictures with film under UV. This summer, I built and verified a set-up for digital capture, and present some pictures of flowers.
My present set-up for digital capture.
Here is columbine.
Here is rhododendron.
Here is catalpa.
NSF and NIH grants, and Students.
Go to stark home page.
This page was last revised 8/22/05