Multiple approaches to unravel chemical cues used by Diachasmimorpha longicaudata during host searching: behavioral, electrophysiological and gene expression studies

SEGURA; DEVESCOVI; WULLF; CONTE; SERGIO M. OVRUSKI; MARIANA M. VISCARRET; SL LANZAVECCHIA; CLADERA, J

Congreso; 6th Internactional Entomophagous Insect Conferences; 2019

Diachasmimorpha longicaudata Ashmead (Braconidae) is one of the most commonly used biocontrol agents against Tephritidae fruit flies pests Females parasitize their hosts during the larval stage, while larvae are still feeding inside the fruit. To this end, females use chemical information which is released from the infested fruit. Our objective is to identify the chemical basis of the attraction of D. longicaudata towards fruit infested by tephritid larvae and address the role of learning on the use of such information. We found that parasitoid females are able to detect fruit infested with larvae using chemical cues, derived from the host larvae, as well as from the substrate (rotten fruit) and associated microorganism, like the fungus Penicillum digitatum. We found that females have innate preference for specific host fruit odors and the basis of this preference seems to be related more to the easiness of attacking host larvae buried into the fruit flesh than to the quality of the host larvae. Color, on the other hand, did not trigger an innate preference in this species. However, D. longicaudata has the ability to associate visual, as well as chemical, cues during host searching, making them more and more efficient at host finding through learning. GC-MS analyses of the volatile compounds released by these attractive sources allowed postulating specific compounds that females would use to locate host larvae, which were then tested in electrophysiological assays. We also performed a functional analysis of chemoreceptors potentially associated to odor detection in this species. A bioinformatic screening of a whole body transcriptome of D. longicaudata, followed by a phylogenetic analysis and a tissue expression profile, allowed to postulate fourteen odorant binding proteins and seven chemosensory proteins. A set of genes were analyzed through behavioral and molecular tests in which gene expression was silenced through RNAi. Preliminary results showed that several of the selected genes are linked to the foraging behavior. This approach aimed at connecting behavioral, electrophysiological and gene expression experiments in order to define potential compounds that could be use in monitoring parasitoid populations as part of biological control programs.