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Ectopic opsin expression in Drosophila: Investigating the spectral sensitivity of Sunburst Diving Beetle larval photoreceptors

Nandamuri, Sri Pratima
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342106178

Abstract Details

2012, MS, University of Cincinnati, Arts and Sciences: Biological Sciences.
The larvae of Sunburst Diving beetle (Thermonectus marmoratus) are highly efficient visually guided predators. The principal eyes of these larvae are extremely unusual among eyes in the animal kingdom. These eyes are long and tubular, with bifocal lenses and two retinas: the distal retina that lies in close proximity to the lens followed by the proximal retina. The unique anatomical and physiological organization of these eyes raises the question of what kind of spectral cues are perceived by the distal and proximal retina. In situ studies have shown that the distal retina expresses a long wavelength sensitive opsin (TmLW) and the proximal retina expresses an ultraviolet sensitive opsin (TmUVII). A recent electrophysiological study on the third instar larvae established the spectral sensitivity of the proximal retina (λmax= 375nm). However, characterization of retinal sensitivity by intracellular recordings in the distal retina has proven difficult. We pursued an alternative method to establish spectral sensitivity of both of these opsins. Using P-element mediated transformation; we ectopically expressed the beetle larval opsins in the major photoreceptors (R1-R6) in Drosophila melanogaster mutants lacking their own functional opsin. Electroretinograms from these flies showed that ectopically expressed beetle opsins are biologically active and capable of coupling to the fly photoreceptor visual transduction cascade. In addition to measuring spectral sensitivity a ¿¿¿¿¿¿¿Subtraction method¿¿¿¿¿¿¿ was employed to compensate for the signal generated from theR7 and R8 photoreceptors still intact in the transgenic Drosophila used in these studies. Our results indicate that the TmLW gene encodes an opsin with peak sensitivity in the blue-green range (487.3 nm), somewhat shorter, than previously predicted from the intracellular beetle photoreceptor recordings. While this could be due to different filtering properties of these very different eyes, we hypothesize that this could be due to differences in chromophore used by T. marmoratus vs. Droosphila opsins. Measurements of the peak sensitivity of the TmUVII opsin were difficult due to overlap with the sensitizing pigment, R7 and R8 photoreceptors, but preliminary studies suggest that it coincides with the previously established intracellular data (375 nm). To our knowledge, this is the first time that ectopic expression of Coleopteran opsins in Drosophila has been reported.
Elke Buschbeck, PhD (Committee Chair)
Tiffany Cook, PhD (Committee Member)
John Layne, PhD (Committee Member)
39 p.
Thermonectus; opsin; spectral sensitivity; Drosophila; chromophore; ;

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Citations

  • Nandamuri, S. P. (2012). Ectopic opsin expression in Drosophila: Investigating the spectral sensitivity of Sunburst Diving Beetle larval photoreceptors [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342106178

    APA Style (7th edition)

  • Nandamuri, Sri Pratima. Ectopic opsin expression in Drosophila: Investigating the spectral sensitivity of Sunburst Diving Beetle larval photoreceptors. 2012. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342106178.

    MLA Style (8th edition)

  • Nandamuri, Sri Pratima. "Ectopic opsin expression in Drosophila: Investigating the spectral sensitivity of Sunburst Diving Beetle larval photoreceptors." Master's thesis, University of Cincinnati, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342106178

    Chicago Manual of Style (17th edition)

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© 2012, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.