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Sensing magnetic directions in birds: radical pair processes involving cryptochrome.

Wiltschko R, Wiltschko W - Biosensors (Basel) (2014)

Bottom Line: Cryptochromes have been suggested as receptor molecules.Cry1a is found in the eyes of birds, where it is located at the membranes of the disks in the outer segments of the UV-cones in chickens and robins.Immuno-histochemical studies show that it is activated by the wavelengths of light that allow magnetic compass orientation in birds.

View Article: PubMed Central - PubMed

Affiliation: Fachbereich Biowissenschaften, J.W. Goethe-Universität Frankfurt, Max von Laue Straße 13, D-60438 Frankfurt am Main, Germany; E-Mail: wiltschko@zoology.uni-frankfurt.de.

ABSTRACT
Birds can use the geomagnetic field for compass orientation. Behavioral experiments, mostly with migrating passerines, revealed three characteristics of the avian magnetic compass: (1) it works spontaneously only in a narrow functional window around the intensity of the ambient magnetic field, but can adapt to other intensities, (2) it is an "inclination compass", not based on the polarity of the magnetic field, but the axial course of the field lines, and (3) it requires short-wavelength light from UV to 565 nm Green. The Radical Pair-Model of magnetoreception can explain these properties by proposing spin-chemical processes in photopigments as underlying mechanism. Applying radio frequency fields, a diagnostic tool for radical pair processes, supports an involvement of a radical pair mechanism in avian magnetoreception: added to the geomagnetic field, they disrupted orientation, presumably by interfering with the receptive processes. Cryptochromes have been suggested as receptor molecules. Cry1a is found in the eyes of birds, where it is located at the membranes of the disks in the outer segments of the UV-cones in chickens and robins. Immuno-histochemical studies show that it is activated by the wavelengths of light that allow magnetic compass orientation in birds.

No MeSH data available.


Localization of cryptochrome 1a (Cry1a) in the retina of robins and chickens. (a) Immuno-labeling of Cry1a and UV-opsin and their co-localization in the retina of robins. A, Vertical section through the outer part of retina; B, whole mount of a retina. (b) Electron-microscopic images of the outer segments of the UV/V-cones, with labeled Cry1a visible as dark dots along the disk membranes. A, entire outer segment of a chicken V-cone. B, higher magnification of the lower part of this outer segment. C, Part of the outer segment of an UV-cone of a robin. (c) Western blots of robin (D) and chicken (E) retina showing Cry1a in the cytosol and membrane fraction. F1, cytosolic fraction; F2, membrane fraction; F3, nuclear fraction; F4, cytoskeletal fraction; T, tongue tissue as control (from [59]).
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biosensors-04-00221-f008: Localization of cryptochrome 1a (Cry1a) in the retina of robins and chickens. (a) Immuno-labeling of Cry1a and UV-opsin and their co-localization in the retina of robins. A, Vertical section through the outer part of retina; B, whole mount of a retina. (b) Electron-microscopic images of the outer segments of the UV/V-cones, with labeled Cry1a visible as dark dots along the disk membranes. A, entire outer segment of a chicken V-cone. B, higher magnification of the lower part of this outer segment. C, Part of the outer segment of an UV-cone of a robin. (c) Western blots of robin (D) and chicken (E) retina showing Cry1a in the cytosol and membrane fraction. F1, cytosolic fraction; F2, membrane fraction; F3, nuclear fraction; F4, cytoskeletal fraction; T, tongue tissue as control (from [59]).

Mentions: The most promising candidate so far is cryptochrome 1a. Using a specific antiserum, Nießner and colleagues [59] found marked Cry1a in a particular type of photoreceptor cells, which was identified by an antiserum against SWS1-opsin as the V-cones of chickens and the UV-cones of robins (Figure 8a). Western blots (Figure 8c) showed Cry1a in the cytosolic and the membrane fraction. In electron-microscopic images, it was found located at the membranes of the disks in the outer segments of both species (Figure 8b). Double labeling indicated that all UV/V cones contain Cry1a, and that Cry1a is in no other cones. Differences between chickens and robins were not observed [59].


Sensing magnetic directions in birds: radical pair processes involving cryptochrome.

Wiltschko R, Wiltschko W - Biosensors (Basel) (2014)

Localization of cryptochrome 1a (Cry1a) in the retina of robins and chickens. (a) Immuno-labeling of Cry1a and UV-opsin and their co-localization in the retina of robins. A, Vertical section through the outer part of retina; B, whole mount of a retina. (b) Electron-microscopic images of the outer segments of the UV/V-cones, with labeled Cry1a visible as dark dots along the disk membranes. A, entire outer segment of a chicken V-cone. B, higher magnification of the lower part of this outer segment. C, Part of the outer segment of an UV-cone of a robin. (c) Western blots of robin (D) and chicken (E) retina showing Cry1a in the cytosol and membrane fraction. F1, cytosolic fraction; F2, membrane fraction; F3, nuclear fraction; F4, cytoskeletal fraction; T, tongue tissue as control (from [59]).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4264356&req=5

biosensors-04-00221-f008: Localization of cryptochrome 1a (Cry1a) in the retina of robins and chickens. (a) Immuno-labeling of Cry1a and UV-opsin and their co-localization in the retina of robins. A, Vertical section through the outer part of retina; B, whole mount of a retina. (b) Electron-microscopic images of the outer segments of the UV/V-cones, with labeled Cry1a visible as dark dots along the disk membranes. A, entire outer segment of a chicken V-cone. B, higher magnification of the lower part of this outer segment. C, Part of the outer segment of an UV-cone of a robin. (c) Western blots of robin (D) and chicken (E) retina showing Cry1a in the cytosol and membrane fraction. F1, cytosolic fraction; F2, membrane fraction; F3, nuclear fraction; F4, cytoskeletal fraction; T, tongue tissue as control (from [59]).
Mentions: The most promising candidate so far is cryptochrome 1a. Using a specific antiserum, Nießner and colleagues [59] found marked Cry1a in a particular type of photoreceptor cells, which was identified by an antiserum against SWS1-opsin as the V-cones of chickens and the UV-cones of robins (Figure 8a). Western blots (Figure 8c) showed Cry1a in the cytosolic and the membrane fraction. In electron-microscopic images, it was found located at the membranes of the disks in the outer segments of both species (Figure 8b). Double labeling indicated that all UV/V cones contain Cry1a, and that Cry1a is in no other cones. Differences between chickens and robins were not observed [59].

Bottom Line: Cryptochromes have been suggested as receptor molecules.Cry1a is found in the eyes of birds, where it is located at the membranes of the disks in the outer segments of the UV-cones in chickens and robins.Immuno-histochemical studies show that it is activated by the wavelengths of light that allow magnetic compass orientation in birds.

View Article: PubMed Central - PubMed

Affiliation: Fachbereich Biowissenschaften, J.W. Goethe-Universität Frankfurt, Max von Laue Straße 13, D-60438 Frankfurt am Main, Germany; E-Mail: wiltschko@zoology.uni-frankfurt.de.

ABSTRACT
Birds can use the geomagnetic field for compass orientation. Behavioral experiments, mostly with migrating passerines, revealed three characteristics of the avian magnetic compass: (1) it works spontaneously only in a narrow functional window around the intensity of the ambient magnetic field, but can adapt to other intensities, (2) it is an "inclination compass", not based on the polarity of the magnetic field, but the axial course of the field lines, and (3) it requires short-wavelength light from UV to 565 nm Green. The Radical Pair-Model of magnetoreception can explain these properties by proposing spin-chemical processes in photopigments as underlying mechanism. Applying radio frequency fields, a diagnostic tool for radical pair processes, supports an involvement of a radical pair mechanism in avian magnetoreception: added to the geomagnetic field, they disrupted orientation, presumably by interfering with the receptive processes. Cryptochromes have been suggested as receptor molecules. Cry1a is found in the eyes of birds, where it is located at the membranes of the disks in the outer segments of the UV-cones in chickens and robins. Immuno-histochemical studies show that it is activated by the wavelengths of light that allow magnetic compass orientation in birds.

No MeSH data available.