The evolutionary history of visual genes in Coleoptera differs from other well-studied insect orders, such as Lepidoptera and Diptera, as beetles have lost the widely conserved short-wavelength (SW) insect opsin gene that typically underpins sensitivity to blue light (∼440nm). Duplications of the ancestral ultraviolet (UV) and long-wavelength (LW) opsins have occurred in many beetle lineages and have been proposed as an evolutionary route for expanded spectral sensitivity. The jewel beetles (Buprestidae) are a highly ecologically diverse and colorful family of beetles that use color cues for mate and host detection. In addition, there is evidence that buprestids have complex spectral sensitivity with up to five photoreceptor classes. Previous work suggested that opsin duplication and subfunctionalization of the two ancestral buprestid opsins, UV and LW, has expanded sensitivity to different regions of the light spectrum, but this has not yet been tested. We show that both duplications are likely unique to Buprestidae or the wider superfamily of Buprestoidea. To directly test photopigment sensitivity, we expressed buprestid opsins from two Chrysochroa species in Drosophila melanogaster and functionally characterized each photopigment type as UV- (356-357nm), blue- (431-442nm), green- (507-509nm), and orange-sensitive (572-584 nm). As these novel opsin duplicates result in significantly shifted spectral sensitivities from the ancestral copies, we explored spectral tuning at four candidate sites using site-directed mutagenesis. This is the first study to directly test opsin spectral tuning mechanisms in the diverse and specious beetles.
Bibliographical noteFunding Information:
We thank Emily Snell-Rood for providing butterfly RNA. We also thank the researchers whose published RNA-seq data were used in this study. This work was supported by NSF grant EAGER-1841704 to N.P.L. and the University of Minnesota College of Biological Sciences to T.J.W.
© 2023 The Author(s). Published by Oxford University Press on behalf of Society for Molecular Biology and Evolution.
- Insect vision
- Spectral tuning
- Visual pigment
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't
- Research Support, U.S. Gov't, Non-P.H.S.