Dragonfly red opsins share a common tuning mechanism with mammalian red opsins and further enhancement of near-infrared sensitivity.

Some animals, such as primates and insects have color vision including sensitivity to red light (red vision). Red vision is basically achieved through opsins sensitive to the red region (red opsins), which independently evolved in different lineages. In dragonfly red vision, which is known to sense longer-wavelength light compared with humans, however, the underlying opsins and the spectral tuning mechanism are largely unknown. Here we investigated dragonfly opsins and found that RhLWA2s are the longest-wavelength-sensitive opsins, so-called red opsins in dragonflies. Spectroscopic analysis of the recombinant pigment of RhLWA2 from Asiagomphus melaenops (Am_RhLWA2) revealed that it has an absorption maximum at 580 nm and exhibits bistability, indicating that Am_RhLWA2 is the longest-wavelength-sensitive bistable opsin to date. Mutational analysis of Am_RhLWA2 revealed that position 292 is responsible for the red shift. The spectral tuning site as well as the mechanism for the red shift (S292A) is shared with that of mammalian red opsins, showing parallel evolution between mammalian and insect green/red opsins, and the substitution from Ala to Val (A292V) in a dragonfly lineage further enhanced the red sensitivity to near-infrared region. Furthermore, we succeeded in engineering red-shifted Am_RhLWA2 mutant having an absorption maximum at 590 nm by introducing V211C mutation. Cultured cells expressing the red-shifted Am_RhLWA2 mutant exhibited significant Ca2+ responses to 738 nm light, showing the potential of near-infrared sensitive optogenetic tools to control GPCR-signaling. Based on the analysis of body coloration of a related dragonfly species, the longer-wavelength sensitivity of Am_RhLWA2 could confer an advantage in sex recognition.