A Photo-Signal Transducing Photoreceptor (Stentorin) in Stentor coeruleus: A Brief Review

Summary

Stentorin acts as the photosensor molecule in the ciliate Stentor coeruleus. This unicellular protozoan is most sensitive to red light (610 nm). Stentor also senses the direction of light propagation, as evidenced by their light-avoiding and negative phototactic swimming behaviors. This aneural photosensory phenomenon is triggered by the photoreceptor stentorin. The possible involvement of a light-induced proton release from the photoreceptor as the primary mechanism of light-signal processing has been discussed. The primary sensory signal, in the form of proton release, triggers subsequent transduction steps that include calcium ion influx from the extracellular medium. It is proposed that the calcium ion influx causes the Stentor cell to reverse its ciliary beating and subsequently steer away from the light trap.