Finding could help explore use of sensitive natural light-sensing proteins in patients with vision disabilities
Can light be sensed without eyes? Researchers from the University of Hyderabad (UoH) say it is possible after a breakthrough study on tiny organisms called ‘planarian flatworms’. These are light-aversive and are known to rely on two sensitive eyes connected to a simple brain to sense light that play a crucial role in controlling their behaviour and movement.
Earlier research has shown planarians can survive even after removal of the head, while retaining the ability to move away from the light source when exposed to low doses of ultraviolet light. How do these organisms sense the light without eyes? Is there any other light-sensing system helping them? The research team led by Akash Gulyani from department of biochemistry, School of Life Sciences at UoH, showed an eye-independent system (extraocular) lining the periphery of the worm’s body allows even a headless flatworm to move like an intact worm with incredible coordination.
Researchers found the worm body to be dotted with a whole array of very unique light sensing cells, especially at the periphery. These newly discovered light sensing cells appear unique as they do not resemble any neuron-like cells and these seem to be very distinct from all light sensing systems known so far across the animal kingdom, said a press release.
Light-sensitive proteins or ‘opsins’ help flatworms to respond to light in the absence of eyes but to a limited range of ultraviolet light at 365 to 395 nm, whereas the flatworm eyes can detect a broad wavelength of visible light (~365 to 625 nm). Interestingly, the eye-independent system arises only in the adults.
Researchers think extraocular light sensing ability of headless worms may help tailpieces escape light and avoid predators. “These findings offer a unique insight into coexistence, development and evolution of independent light-sensing systems in a single organism,” conclude the authors. This could help explore use of such sensitive natural light sensing proteins for helping patients with vision disabilities to ‘sense’ light and to control inner working of cells/tissues with light (optogenetics).
The work was done in collaboration with Dasaradhi Palakodeti, inStem, Bengaluru and has been published in ‘Proceedings of the National Academy of Sciences (USA).
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