CRISPR disruption of optix in tobacco hawkmoth replaces orange pigmentation with black eumelanin

Research on colour patterning in Lepidoptera has established a conserved genetic toolkit that includes the homeobox transcription factor optix, previously shown to regulate ommochrome and melanin pigmentation and structural coloration in nymphalid butterflies. Whether optix plays equivalent roles in other insect groups has remained unclear.

A preprint deposited on bioRxiv (20 August 2026) describes the use of CRISPR-Cas9 to disrupt optix in the tobacco hawkmoth Manduca sexta, a species outside the Nymphalidae. Loss of optix function produced a striking abdominal pigmentation phenotype: orange pigmentation was replaced by black eumelanin, confirmed by chemical analysis. The result demonstrates that the role of optix in colour patterning is not confined to nymphalid butterflies and suggests it may act as a broader regulator of lepidopteran pigmentation programmes.

The study contributes to understanding of how a limited set of transcription factors can be repeatedly deployed across distantly related lineages to pattern colour, a question relevant to evolutionary developmental biology and the genetics of adaptation. As a preprint, this work has not yet completed peer review and the findings should be interpreted accordingly.