Host regulation by the ectophagous parasitoid wasp Bracon nigricans. (August 2017)

• Record Type: Journal Article
• Authors: Becchimanzi, Andrea; Avolio, Maddalena; Di Lelio, Ilaria; Marinelli, Adriana; Varricchio, Paola; Grimaldi, Annalisa; de Eguileor, Magda; Pennacchio, Francesco; Caccia, Silvia
• Is Part Of: Journal of insect physiology. Volume 101(2017:Jun.)
• Page Start: 73
• Page End: 81
• Publication Date: 2017-08
• Subjects: Parasitic Hymenoptera -- Host-parasitoid interactions -- Immunosuppression -- Venom -- Haemocytes; Insects -- Physiology -- Periodicals; Insectes -- Physiologie -- Périodiques; Insects -- Physiology; Periodicals; 571.157
• DOI: 10.1016/j.jinsphys.2017.07.002
• Languages: English
• ISSNs: 0022-1910

Abstract

Graphical abstract: Highlights: Parasitism causes paralysis of the host and its metabolic/biochemical redirection. Venom is the major host regulation factor involved. Haemocytes mediate the mobilization of nutrients stored in the fat body. Fat body degradation is associated with a localized activity of cathepsin L. Abstract: The host regulation process has been widely investigated in endophagous parasitoid wasps, which in most cases finely interact with living hosts (i.e. koinobiont parasitoids). In contrast, only very limited information is available for ectophagous parasitoids that permanently paralyze and rapidly suppress their victims (i.e. idiobiont parasitoids). Here we try to fill this research gap by investigating the host regulation by Bracon nigricans, an ectophagous idiobiont wasp species. Parasitism, mainly by venom action, is able to redirect host metabolism in order to enhance its nutritional suitability for the developing parasitoid larvae and to provide the required metabolic support to host tissues. The observed alterations of the host titers of haemolymph proteins, carbohydrates and acylglycerols are associated with a parasitoid-induced mobilization of nutrients stored in the fat body. This tissue undergoes a controlled degradation mediated by a close surface interaction with haemocytes, where a cathepsin L activity is localized, as demonstrated by immunolocalization, biochemical and transcriptional data . B. nigricans parasitism does not markedly influence the survival of haemocytes, even though a persistent suppression of the immune competence is observed in parasitized hosts, which show a reduced capacity to encapsulate and melanize non-self objects. These immune alterations likely allow a more efficient food uptake and use by the ectophagous larvae. The obtained results indicate that the host regulation process in basal lineages of parasitic Hymenoptera is more complex than expected and shares functional similarities with adaptive strategies occurring in derived koinobiont species.