Researchers at Osaka Metropolitan University, Japan, have discovered a light-activated protein in dragonflies that enable them to detect deep-red light at wavelengths of up to 720 nm (Cell. Mol. Life Sci., doi: 10.1007/s00018-025-06017-9). By pinpointing and modifying the molecular mechanisms that enable such long-wavelength sensitivity, the team has created a version of the protein that could be used to activate cells deep within living organisms using near-infrared light.

More light-sensitive proteins

Color vision in most animals is mediated by proteins, called opsins, that are bound to a light-sensitive molecule. Small variations in the protein structure provide sensitivity to different colors, with humans having three types of opsins to detect blue, green and red light. Dragonflies, meanwhile, have evolved a much larger number of structural variants, allowing them to achieve precise color sensitivity over wavelengths ranging from the ultraviolet to the far edge of the red spectrum.

In this study, the researchers measured the absorption spectra for a selection of dragonfly opsins that are sensitive to deep-red light. One of these was found to have an absorption peak at 580 nm, with the ability to detect wavelengths just beyond 700 nm. Further analysis revealed that this long-wavelength response is achieved through the same molecular mechanism that enables humans and some other mammals to see deep-red colors—a rare example of a parallel but independent evolutionary process.

The researchers hypothesized that this strong sensitivity to deep-red light might help dragonflies identify suitable mates during high-speed flight. They measured the light reflected from yellow stripes on the bodies of male and female dragonflies that possess the red-sensitive opsin. Small differences in coloration were observed at wavelengths above 530 nm, which could be distinguished more easily with a visual system that is sensitive to longer wavelengths.

Toward a significant red shift 

The researchers also showed that they could modify the spectral response of the opsin by replacing an amino acid at one specific location with one from mantis shrimp, the only other creature that is known to detect light at even longer wavelengths. This mutated version of the protein exhibits a significant red shift, with the absorption peak moving by about 10 nm. When irradiated with near-infrared light at 738 nm, the cellular response of the red-shifted variant was 10 times stronger than for the naturally occurring opsin.

The findings from this study offer new opportunities for optogenetics, in which light is used to activate a cellular response within living organisms. The researchers believe that the red-shifted variant of the dragonfly’s opsin is likely to be more sensitive to near-infrared light than existing molecular agents, potentially allowing more effective activation in deeper parts of the body.