Avolio, Maddalena (2015) Functional and molecular analysis of venom produced by the ectoparasitoid Bracon nigricans. [Tesi di dottorato]

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Item Type: Tesi di dottorato
Lingua: English
Title: Functional and molecular analysis of venom produced by the ectoparasitoid Bracon nigricans.
Creators:
CreatorsEmail
Avolio, Maddalenaavoliomaddalena@hotmail.com
Date: 30 March 2015
Number of Pages: 123
Institution: Università degli Studi di Napoli Federico II
Department: Agraria
Scuola di dottorato: Scienze agrarie e agroalimentari
Dottorato: Scienze delle risorse ambientali
Ciclo di dottorato: 27
Coordinatore del Corso di dottorato:
nomeemail
Rao, Maria Antoniettamariarao@unina.it
Tutor:
nomeemail
Pennacchio, FrancescoUNSPECIFIED
Quiroz, AndrésUNSPECIFIED
Date: 30 March 2015
Number of Pages: 123
Uncontrolled Keywords: Bracon; venom; ectoparasitoid
Settori scientifico-disciplinari del MIUR: Area 07 - Scienze agrarie e veterinarie > AGR/13 - Chimica agraria
Date Deposited: 13 Apr 2015 13:08
Last Modified: 08 May 2016 01:00
URI: http://www.fedoa.unina.it/id/eprint/10231
DOI: 10.6092/UNINA/FEDOA/10231

Abstract

Parasitoid wasps have evolved a variety of strategies to regulate the physiology of their hosts in order to regulate the host's immunity and physiology for the interest of the development of its offspring. The venom of parasitic Hymenoptera, one of the major actors in the host regulation, has the potencial for developing novel environmentally safe insect control strategies and it is a blend of biologically, pharmacologically and physiologically complex mixture of peptides, amines, proteinaceous and nonproteinaceaous compounds). The neurotoxicity of the components present in the venom of Bracon species stimulated considerable research interests in this area, with the aim of isolating new agrochemical leads. However, the characterization of venom produced by Bracon species is restricted to B. hebetor, B. brevicornis and B. gelechie. In B. hebetor, paralytic activity is mediated by three partially characterized proteins that presynaptically block glutaminergic transmission , and other unknow factors seem to affect host endocrine balance and metabolic activity. In this work the interaction between ectoparasitoids and their hosts has been analyzed in the B. nigricans - Spodoptera littoralis model. The parasitism does not induce a rapid suppression of the host, even though the unaltered viability of hemocytes is associated with a suppression of their cellular division and/or production by haematopoietic organs. However, clear signs of a more subtle host regulation are evident, such as the reduction of CO2 emission and the significant increase of hemolymph proteins and carbohydrates. The resulting enhancement of host nutritional suitability is associated with the success of progeny development and structural changes of the fat body cells, which interact with hemocytes and show signs of cell degeneration. The combined approaches of transcriptomic analysis on venom glands and proteomic study on crude venom resulted in the identification of several proteins, including a putative phospholipase A2 of 17 kDa. This protein is probably the main toxin involved in the paralytic activity of B. nigricans venom. Additionally, a chromatographic fraction containing a protein band of about 17 kDa induces, when injected, a temporary paralysis in S. littoralis larvae. The identification of this protein and the production of recombinant phospholipase A2 will provide explanations on the functional role played by this bioactive component in the host regulation process. Finally, as required by the PhD program, I have spent a period abroad where I studied the effects of silver nanoparticles against the red clover root borer, Hylastinus obscurus (Marsham) (Coleoptera: Curculionidae). Bioassays with silver nanoparticles showed that nanoparticles act as a feeding deterrent.

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