Functional characterization of PBP1 gene in Helicoverpa armigera (Lepidoptera: Noctuidae) by using the CRISPR/Cas9 system

Pheromone binding proteins (PBPs) are thought to play crucial roles in perception of the sex pheromones particularly in noctuid moths, but this is rarely in vivo evidenced due to lacking an effective technique. Here, we reported an in vivo functional study of PBP1 in the important lepidopteran pest Helicoverpa armigera (HarmPBP1), by using the CRISPR/Cas9 system. Efficient and heritable mutagenesis was achieved by egg injection of mixture of Cas9-mRNA and HarmPBP1-sgRNA. The TA cloning and sequencing revealed various insertion and/or deletion (indel) mutations at the target site. Among those, one mutation resulted in a premature stop codon at the target site, which led to a highly truncated protein with only 10 amino acids. The HarmPBP1 with this mutation would completely loss its function, and thus was used to select the homozygous mutant insects for functional analysis. The electroantennogram recording showed that the mutant male adults displayed severely impaired responses to all three sex pheromone components (Z11-16:Ald, Z9-16:Ald and Z9-14:Ald). Our study provides the first in vivo evidence that HarmPBP1 plays important role in perception of female sex pheromones, and also an effective methodology for using CRISPR/Cas9 system in functional genetic study in H. armigera as well as other insects.