Photoreceptor protein
Photoreceptor proteins are light-sensitive
Structure
Photoreceptor proteins typically consist of a
Photoreceptors in animals
- Melanopsin: in vertebrate retina, mediates pupillary reflex, involved in regulation of circadian rhythms
- Photopsin: reception of various colors of light in the cone cellsof vertebrate retina
- Rhodopsin: green-blue light reception in the rod cells of vertebrate retina
- Protein Kinase C: mediates photoreceptor deactivation, and retinal degeneration[5]
- UV-light[6]
Photoreceptors in plants
- UVR8: UV-B light reception
- Cryptochrome: blue and UV-A light reception
- Phototropin: blue and UV-A light perception (to mediate phototropism and chloroplast movement)
- Zeitlupe: blue light entrainment of the circadian clock
- Phytochrome: red and far-red light reception
All the photoreceptors listed above allow plants to sense light with wavelengths range from 280 nm (UV-B) to 750 nm (far-red light). Plants use light of different wavelengths as environmental cues to both alter their position and to trigger important developmental transitions.[7] The most prominent wavelength responsible for plant mechanisms is blue light, which can trigger cell elongation, plant orientation, and flowering.[8] One of the most important processes regulated by photoreceptors is known as photomorphogenesis. When a seed germinates underground in the absence of light, its stem rapidly elongates upwards. When it breaks through the surface of the soil, photoreceptors perceive light. The activated photoreceptors cause a change in developmental program; the plant starts producing chlorophyll and switches to photosynthetic growth.[9]
Photoreceptors in phototactic flagellates
(Also see: Eyespot apparatus)
- Channelrhodopsin: in unicellular algae, mediates phototaxis
- Chlamyopsin and volvoxopsin
- Flavoproteins