Identification of the ubiquitous antioxidant tripeptide glutathione as a fruit fly semiochemical

Authors: CHESETO, XAVIER - International Centre Of Insect Physiology And Ecology; KACHIGAMBA, DONALD - Bvumbwe Agricultural Research Station; EKESI, SUNDAY - International Centre Of Insect Physiology And Ecology; NDUNG'U, MARY - Jomo Kenyatta University; Teal, Peter; Beck, John; TORTO, BALDWYN - International Centre Of Insect Physiology And Ecology

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2017
Publication Date: 9/15/2017
Citation: Cheseto, X., Kachigamba, D., Ekesi, S., Ndung'U, M., Teal, P.E., Beck, J.J., Torto, B. 2017. Identification of the ubiquitous antioxidant tripeptide glutathione as a fruit fly semiochemical. Journal of Agricultural and Food Chemistry. doi:10.1021/acs.jafc.7b03164.

Interpretive Summary: Many insects mark the sites where they have lain eggs with an odor (host marking pheromone) to deter other females from egg-laying at that site, thus preventing too many eggs at one site. Previous studies have identified these types of insect odors and used them to manipulate the behavior of certain fruit fly species. Fruit flies are common insect pests of many agricultural products, worldwide. However, few examples are known for African indigenous fruit flies. Here, we show that the egg odor of the African fruit fly is a common animal and plant compound known as glutathione (GSH). In this study, GSH was identified as an active compound from the water extract of adult female fecal matter. GSH level increased with increasing age of female fecal matter, with the most amounts detected in the fecal matter of ~ 2-week-old adult females. Additionally, it was found that GSH level was 5-10-fold higher in fecal matter than in the ovipositor and hemolymph extracts of females. In bioassays, synthetic GSH reduced oviposition responses in similar species of fruit flies. These results document in a first report the involvement of a common compound of this type as an odor that affects behavior in insects, and more importantly how this compound could be potentially used for fruit fly management.

Technical Abstract: Many insects mark their oviposition sites with a host marking pheromone (HMP) to deter other females from over-exploiting these sites for egg-laying. Previous studies have identified and used HMPs to manage certain fruit fly species. However, few examples are known for African indigenous fruit flies. Here, we show that the HMP of the African fruit fly Ceratitis cosyra, is the ubiquitous animal and plant antioxidant tripeptide, glutathione (GSH). We identified GSH using bioassay-guided fractionation and analysis of the aqueous extract of adult female fecal matter by LC-Qtof-MS, and acid hydrolysis of the natural product into its amino acids; glycine, cysteine and glutamic acid. GSH level increased with increasing age of female fecal matter, with optimal amounts detected in the fecal matter of ~ 2-week-old adult females. Additionally, we found that GSH level was 5-10-fold higher in fecal matter than in the ovipositor and hemolymph extracts of females. In bioassays, synthetic GSH reduced oviposition responses in conspecifics of C. cosyra and the heterospecific species C. rosa, C. fasciventris, C. capitata and Zeugodacus cucurbitae. Our results document the first report of the involvement of a ubiquitous antioxidant as a semiochemical in insects, and its potential use in fruit fly management.