Abstract 1430 MALDI Spatial Imaging to Characterize the Competition for Metabolic Resources During Parasitoid Wasp Infection of Fly Larvae

Parasitoid wasps are a large (∼150,000 species) group of hymenopterans that are obligate parasites of various insects and are often used in biocontrol as they lead to the death of their host. Ganaspis hookeri is an endo-parasitoid of Drosophila species. Parasitic infection occurs by the injection of the wasp egg into the fly larva. To combat its demise, the larva mounts a cellular immune response wherein hemocytes differentiate into lamellocytes that recognize and surround the egg leading to melanization and death of the wasp. To counter, the wasp also injects venom proteins that act by various mechanisms to blunt the fly's immune response. In addition to initiating an immune response, parasitoid infection alters larval metabolism. Energy production in immune cells is shifted from oxidative phosphorylation to glycolysis. In the fat body, a liver- and adipose-like tissue, gluconeogenesis is stimulated and glycogen and triacylglycerol storage are inhibited in favor of fatty acid and glucose generation. The venom of G. hookeri contains 168 proteins including most of the glycolytic enzymes, many TCA cycle enzymes, fatty acid synthase, the ATP synthase beta subunit and other metabolic enzymes. Our objective is to understand how venom metabolic enzymes contribute specifically to the viability of the parasitoid rather than that of the fly. We hope to use mass spectrometry imaging to characterize the spatial and temporal changes in lipids, proteins, and metabolites that occur upon wasp infection of Drosophila larvae. We have recently acquired the Bruker timsTOF fleX MALDI-2 instrument (SUNY Albany) and are developing methodologies to image various tissues/structures in the Drosophila larva. The small size of the fly larva poses a challenge in the preparation of samples and the collection of mass spectrometry data. In preliminary work, we have observed striking localization of various lipids that appear to distinguish the larval fat body, gut and hemolymph, and perhaps body wall muscle. These designations are supported by classical histological staining. To corroborate our preliminary designation of larval tissues by mass spectrometry imaging, we will also use Drosophila larvae that express beta-galactosidase in a tissue-specific fashion to determine whether Xgal staining matches the mass spectrometry lipid localizations. These studies will lay the groundwork for future proteomic, lipidomic and metabolomic characterization of the fly-wasp metabolic competition. This work was supported by the Siena College Biology Department (RSM), the Siena Center for Undergraduate Research and Creative Activity (RSM, TJA, CBS), by NSF MRI 2216089 to Y. Liang (PI), R. Linhardt, R. Sterne-Marr, J. Sheng and A. Valm (Co-PIs) (RSM), and NIH R35GM133760 (NTM).