Antennal transcriptome analysis reveals sensory receptors potentially associated with host detection in the livestock pest Lucilia cuprina

Authors: WULFF, JUAN - North Carolina State University; Hickner, Paul; WATSON, DAVID - North Carolina State University; DENNING, STEVEN - North Carolina State University; BELIKOFF, ESTHER - North Carolina State University; SCOTT, MAXWELL - North Carolina State University

Submitted to: Parasites & Vectors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Background: Lucilia cuprina, the Australian sheep blowfly, is the primary fly causing flystrike of sheep in Australia and New Zealand. Adult females lay their eggs in an open wound or natural orifice, and the developing larvae feed on the host’s tissues, a condition called myiasis. Our aim was to improve our understanding of host seeking behavior by conducting gene expression analysis of the antennae of males and females eliciting different olfactory behaviors. Methods: An olfactometer was used to test attraction of L. cuprina males and gravid females to fresh or rotting beef. Antennal RNA-seq analysis was used to identify sensory receptors differentially expressed between sexes. Results: L. cuprina females were more attracted to rotten beef compared to fresh beef. However, males and some females did not respond to either type of beef. Gene expression analysis was conducted on antennae dissected from attracted females, non-attracted females, and males. 153 genes from 11 gene families associated with sensory perception were expressed in the antennae. Of those, 64 were differentially expressed in at least one of the comparisons. Conclusions: Among the differentially expressed genes, the most promising candidates to be evaluated through functional assays were a female-biased odorant receptor (LcupOR46), a female-biased ammonia transporter (AMT_Rh50), and an ABC transporter (ABC G23.1) that was upregulated in the antennae of females attracted to rotting beef compared to non-attracted females. Further, this is the first report suggesting a possible role for ABC transporters in L. cuprina olfaction, and potentially in other insects.

Technical Abstract: Background: Lucilia cuprina (Wiedemann, 1830) (Diptera: Calliphoridae) is the main causative agent of flystrike of sheep in Australia and New Zealand. Female flies lay their eggs in an open wound or natural orifice, and the developing larvae eat the host’s tissues, a condition called myiasis. With the aim of improving our understanding of host seeking behavior, we quantified gene expression in male and female antennae based on their behavior. Methods: A spatial olfactometer was used to evaluate the olfactory response of L. cuprina mated males and gravid females to fresh or rotting beef. Antennal RNA-Seq analysis was used to identify sensory receptors differentially expressed between groups. Results: L. cuprina females were more attracted to rotten beef compared to fresh beef (> 5-fold increase). However, males and some females did not respond to either type of beef. RNA-Seq analysis was performed on antennae dissected from attracted females, non-attracted females and males. Transcripts encoding sensory receptors from 11 gene families were identified above a threshold (= 5 transcript per million) including: 49 ATP-binding cassette transporters (ABCs); two ammonium transporters (AMTs); 37 odorant receptors (ORs); 16 ionotropic receptors (IRs); five gustatory receptors (GRs); 22 odorant-binding proteins (OBPs); nine CD36-sensory neuron membrane proteins (CD36/SNMPs); four chemosensory proteins (CSPs); four myeloid lipid-recognition (ML) and Niemann-Pick C2 disease proteins (ML/NPC2); two pickpocket receptors (PPKs); and three transient receptor potential channels (TRPs). Differential expression analyses identified sex-biased sensory receptors. Conclusions: We identified differentially expressed sensory receptors between the antennae of both sexes and suggested receptors potentially associated with host detection by females. The most promising candidates to be evaluated through functional assays were a female-biased odorant receptor (LcupOR46), a female-biased ammonia transporter (AMT_Rh50) and an ABC transporter (ABC G23.1) that was upregulated in the antennae of females attracted to rotting beef compared to non-attracted females. Further, this is the first report suggesting a possible role for ABC transporters in L. cuprina olfaction, and potentially in other insects.