Knockout of the LW opsin gene interferes with oviposition selection of nocturnal moth, Helicoverpa armigera.

Diurnal insects can select suitable oviposition sites by discriminating plant coloration. The long wavelength sensitive opsin (LW) gene is mainly for discriminating long wavelengths of colors in diurnal insects. However, the affection of coloration on oviposition selection and the roles of LW gene in nocturnal insects are unclear. Here, the questions were explored in Helicoverpa armigera (Lepidoptera, Noctuidae) using CRISPR/Cas9 gene editing technology and experiments of oviposition selection under different coloration backgrounds. To different brightness (achromatic white, grey, black), wild moths preferred to oviposit on higher-brightness background, while the LW mutant had no preference. To different colors, wild moths had no oviposition preference, while the LW mutant significantly reduced oviposition on long-wavelengths of colors (red, orange, yellow, and green) compared to blue and violet. When both brightness (white) and color (orange and green) cues were presented for oviposition, wild moths were more attracted to brightness than color, while LW mutant had no significant preference. For the coloration of young and old leaves, wild moths preferred to oviposit on coloration of young leaves that had a brighter light green, while LW mutant had no preference. Electroretinogram recordings showed that the responses of moths to different bright light or different color light were significantly decreased after knockout of LW, especially to the long-wavelengths. These results suggest that brightness is a more reliable cue rather than color for oviposition selection of nocturnal moth H. armigera in changing microhabitats and LW mediates the recognition of different brightness and long wavelengths. [ABSTRACT FROM AUTHOR]