Investigating the effects of the male lures cue-lure and zingerone on gene expression in Bactrocera tryoni and Bactrocera jarvisi (Diptera: Tephritidae)

Abstract

True fruit flies are a globally significant group of insect pest species capable of severely damaging commercial crops, and thus they are actively managed. Plant secondary metabolites, including methyl eugenol, cue-lure, and zingerone, elicit a positive response in male fruit flies. These male lures are employed in trapping fruit flies, either for monitoring purposes or as part of a male annihilation technique aimed at suppressing the population of fruit flies. Research has demonstrated that male lures can have various biological effects in fruit flies, and that these effects can vary between and within species and lure types. Not only does investigating these effects improve the understanding of the complex relationship between male lures and fruit flies, but this knowledge has potential applications in pest management strategies for advantageously modifying fruit fly biology. The use of transcriptomics in this field is relatively limited, therefore, this study aimed to investigate the effects of lure feeding on gene expression across different lures, species, and generations. Two separate studies were conducted, the first investigated differential gene expression in Bactrocera tryoni and Bactrocera jarvisi fed cue-lure and zingerone, and the second investigated differential gene expression in B. tryoni fed cue-lure and their offspring. To our knowledge, this is the first report of viral upregulation in a fruit fly in response to a lure; across both studies iflavirus transcripts were found upregulated in cue-lure fed B. tryoni. In the first study, 262 genes were differentially expressed in cue-lure fed B. tryoni, 238 in zingerone fed B. tryoni, 159 in cue-lure fed B. jarvisi, and 176 in zingerone fed B. jarvisi. Transposable element-related genes were differentially expressed in all treatments and differentially expressed sensory-related genes (e.g. general odorant binding protein 56a-like and general odorant binding protein 99a-like) varied across lure type and species. In the second study, 282 genes were differentially expressed in cue-lure fed flies in B. tryoni parents and 102 in their offspring. Across cue-lure fed parents and offspring, 39 genes were consistently differentially expressed, indicating that these genes could be involved in the generational effects of cue-lure in B. tryoni. These two studies have been able to provide new insights into the effects of male lures at the gene expression level and identify candidate genes for further functional analyses. These results will help improve the understanding of male lures in fruit flies and may have implications in pest management.