Regulation of photosensation by hydrogen peroxide and antioxidants in C. elegans

The eyeless C . elegans exhibits robust phototaxis behavior in response to short-wavelength light, particularly UV light. C . elegans senses light through LITE-1, a unique photoreceptor protein that belongs to the invertebrate taste receptor family. However, it remains unclear how LITE-1 is regulated. Here, we performed a forward genetic screen for genes that when mutated suppress LITE-1 function. One group of lite-1 suppressors are the genes required for producing the two primary antioxidants thioredoxin and glutathione, suggesting that oxidization of LITE-1 inhibits its function. Indeed, the oxidant hydrogen peroxide (H 2 O 2 ) suppresses phototaxis behavior and inhibits the photoresponse in photoreceptor neurons, whereas other sensory behaviors are relatively less vulnerable to H 2 O 2 . Conversely, antioxidants can rescue the phenotype of lite-1 suppressor mutants and promote the photoresponse. As UV light illumination generates H 2 O 2 , we propose that upon light activation of LITE-1, light-produced H 2 O 2 then deactivates LITE-1 to terminate the photoresponse, while antioxidants may promote LITE-1’s recovery from its inactive state. Our studies provide a potential mechanism by which H 2 O 2 and antioxidants act synergistically to regulate photosensation in C . elegans .