Publication details

Defence reaction against nematobacterial infection in Drosophila melanogaster: a role for the adipokinetic hormone and adenosine



Year of publication 2016
Type Conference abstract
MU Faculty or unit

Faculty of Science

Description Entomopathogenic nematodes are multicellular insect parasites which are symbiotically associated with particular species of bacteria forming together highly pathogenic complex. This complex represents a severe stress for the infected insect that must activate its anti-stress defence system. It is supposed that adipokinetic hormone (AKH), important stress hormone responsible for keeping homeostasis in insect body, and adenosine, a purine nucleotide that serves as signalling factor in anti-stress reaction on both cellular and organismal levels, play a role in defence reaction against the infection. To verify this, the Drosophila melanogaster mutants producing (1) defect non-functional AKH (AKH-def) and (2) impaired adenosine receptor (AdoR-def), and two nematodal species Steinernema carpocapsae and Heterorhabditis bacteriophora were used in our study. The results revealed that both AKH-def and AdoR-def flies infected by the nematodes showed significantly lower mortality (1.9 and 1.7 times, respectively) than the control with AKH- and AdoR-normal production. Further, application of external AKH by dipping of experimental larvae into the Drome-AKH solution (3 pmol Drome-AKH/ul 20% MeOH) significantly increased the mortality (up to 1.8 fold). It seems that the AKH absence reduced production of nutrients into the haemolymph, which inhibited the infection development. And vice versa the application of AKH restored production of energy rich metabolites and supported the infection. Indeed, a level of trehalose was significantly lower (0.6 fold) in untreated AKH-def, and higher in untreated AdoR-def (1.8 fold) Drosophila mutants than that in control. In nematode treated mutants the trehalose level was significantly lower in both AKH-def (0.4 times) and AdoR-def (0.7 times). Those indicate clear stimulatory role of AKH, and minor modulatory role of adenosine in regulation of the trehalose level in Drosophila haemolymph. Similar changes, however not so considerable, were recorded for level of glucose and also lipids; negligible changes were recorded for proteins. It is indisputable that the nematode infection is stressing for the Drosophila organism and that is accompanied by higher production of Drome-AKH by the corresponding cells in the ring gland (up to 1.6 fold), and by the raising of all studied nutrients (with the exception of proteins) in haemolymph (max. trehalose 2.6 times). Nevertheless, the mechanism of action of the nematode infection is not quite clear yet, because the results of the total metabolism determination monitored by the carbon dioxide production suggest that more players are involved in the phenomenon. Our research was supported by the grants KONTAKT No. LH 14047 (Ministry of Education, Youth and Sports, CR) and No. 14-07172S (Czech Science Foundation). The stay of EI in the University of South Bohemia was supported by the Missions Department in Cairo, Egypt.
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