Feedback from rhodopsin controls rhodopsin exclusion in Drosophila photoreceptors

Some of the senses, such as colour vision and olfaction, rely on single sensory neurons to produce a specific chemical- or light-sensing G-protein coupled receptor. Various mechanisms have been proposed to explain exclusive gene expression in olfactory receptors, but the molecular pathways remain unknown. Claude Desplan and colleagues report that mature Drosophila R8 photoreceptors of the subtype that normally expresses green-sensing rhodopsin 6 protein can express the 'wrong' blue-sensing rhodopsin 5 when fruitflies are either kept in the dark or mutated in rhodopsin 6. Light thus achieves a negative feedback on the rh5 gene by repressing its transcription in rh6-expressing neurons, a system resembling the control of olfactory receptor genes in vertebrate olfactory neurons.