CRISPR/Cas9‐mediated knockout of LW‐opsin reduces the efficiency of phototaxis in the diamondback moth Plutella xylostella

Abstract

BACKGROUND: Opsins are crucial for animal vision. The identity and function of opsins in Plutella xylostella remain unknown. The aim of the research is to confirm which opsin gene(s) contribute to phototaxis of P. xylostella.RESULTS: LW-opsin, BL-opsin and UV-opsin, were identified in the P. xylostella genome. LW-opsin was more highly expressed than the other two opsin genes, and all three genes were specifically expressed in the head. Three P. xylostella strains, LW-13 with a 13-bp deletion in LW-opsin, BL + 2 with a 2-bp insertion in BL-opsin, and UV-29 with a 5-bp insertion and a 34-bp deletion in UV-opsin, were established from the strain G88 using the CRISPR/Cas9 system. Among the three opsin-knockout strains, only male and female LW-13 exhibited weaker phototaxis to lights of different wavelengths and white light than G88 at 2.5 lx due to defective locomotion, and LW-13 was defective to sense white, green and infrared lights. The locomotion of LW-13 was reduced compared with G88 at 2.5, 10, 20, 60, 80, 100, and 200 lx under the green light, but the locomotion of LW-13 female was recovered at 80, 100 and 200 lx. The defective phototaxis to the green light of male LW-13 was not affected by light intensity, while the defective phototaxis to the green light of female LW-13 was recovered at 10, 20, 60, 80, 100, and 200 lx. CONCLUSION: LW-opsin is involved in light sensing and locomotion of P. xylostella, providing a potential target gene for controlling the pest.

An LW-Opsin Mutation Changes the Gene Expression of the Phototransduction Pathway: A Cryptochrome1 Mutation Enhances the Phototaxis of Male Plutella xylostella (Lepidoptera: Plutellidae)

“…LW-opsin is a gene with an absolute dominance expression compared with other opsins in P . xylostella [ 17 ]. Differentially-expressed genes caused by an LW-opsin mutation in P .…”

“…xylostella strains were used in the study. Geneva 88 (G88) was employed as a wild type, and the other two mutant strains, namely, LW-13 (a 13-bp deletion in LW-opsin ) [ 17 ] and Cry1-KO (a 2-bp deletion in cryptochrome1 ) [ 18 ] were developed in a G88 background by using the CRISPR/Cas9 technology. The larvae were reared on an artificial diet (Frontier Scientific Services, Newark, DE, USA), and the adults were fed with a 10% honey solution.…”

“…The light intensity was 2.5 lux and the phototactic rate (%) = (the number of months in the illuminated room/total number of moths for the experiment) × 100. The details of the phototactic-behavior assays have been described previously [ 17 ]. All the experiments were repeated four times.…”

“…Opsins covalently bind to small molecular chromophores to form light-sensitive photopigments—rhodopsins—which initiate the phototransduction cascade [ 2 , 4 ]. Opsins contribute to phototactic behaviors in insects, such as Drosophila [ 13 ], Nephotettix cincticeps (Uhler, 1896) (rice green leafhopper, Hemiptera: Cicadellidae) [ 14 ], Spodoptera exigua (Hübner, 1808) (beet armyworm, Lepidoptera: Noctuidae) [ 15 ], Diaphorina citri (Kuwayama, 1908) (Asian citrus psyllid, Hemiptera: Liviidae) [ 16 ], and Plutella xylostella (Linnaeus, 1758) (diamondback moth, Lepidoptera: Plutellidae) [ 17 ]. These studies, however, only focus on the function of opsin, and research is lacking on changes in the expression levels of other genes in the phototransduction pathway caused by an opsin mutation.…”

“…The mutation of LW-opsin results in the defective phototaxis of P . xylostella [ 17 ]. The changes in the expression levels of other genes in the phototransduction pathway caused by the opsin mutation remain unknown in P .…”