Metarhizium anisopliae s.l. modulation of lipid metabolism during tick infection is independent of AMPK and ERK pathways

Despite the importance of fat body in metabolism of arthropods, studies in ticks are scarce. This study evaluated the lipid composition and activation of extracellular signal-regulated protein kinase (ERK) and AMP-activated protein kinase (AMPK) enzymes in Rhipicephalus microplus fat body after infection with different isolates of the fungus Metarhizium anisopliae sensu lato (Metschnikoff, 1879) Sorokin, 1883. The isolates CG 32, GC 112, GC 148, GC 347, and GC 629 were inoculated as viable or non-viable conidia in the ticks. The engorged females were dissected, and their fat bodies were collected 24 and 48 h after infection. The lipid composition was assessed by thin layer chromatography, and enzyme activation was detected by Western blotting with antibodies against p-AMPK and p-ERK. The study showed increased levels of triacylglycerol 24 and 48 h and fatty acid after 48 h after inoculation with different isolates of viable fungi in the tick’s hemocoel. Detection of the active form of ERK was demonstrated only after inoculation with non-viable conidia of all isolates tested. The active form of AMPK, only isolate CG 112 was able to activate with viable or non-viable conidia, whereas isolates CG 32 and CG 629 were able to activate with non-viable conidia. This study provides the first report about changes in important metabolic pathways in ticks infected with entomopathogenic fungi and suggests that the lipid content is modulated by non-usual pathways. However, further studies may be necessary for a better elucidation of this interaction.