Understanding Virulence Mechanisms of Parasitoid Wasps of Drosophila: A Comparative Approach Across Clades

<p>In a rapid and precise self-defense reaction, larvae of many <em>Drosophila</em> species encapsulate parasitoid wasps’ eggs to inhibit wasp development. Parasitoid wasps of the genus <em>Leptopilina</em> are known to produce extracellular vesicle (EV)-like secretions in their venom. Well-characterized in <em>L. heterotoma</em>, these vesicles kill host hemocytes, respectively, such that the encapsulation response in <em>D. melanogaster</em> is suppressed. A putative virulence protein, SSp40 in <em>L. heterotoma</em> EVs, triggers lamellocyte lysis. SSp40 is structurally similar to the bacterial IpaD and SipD proteins. The immune-suppressive mechanisms of closely related heterotoma clade wasps, <em>L. victoriae</em>, <em>L. pacifica</em>, and <em>L. guineaensis</em>, are not understood. We show that these closely related wasps exhibit markedly distinct abilities to suppress encapsulation in wild-type <em>D. melanogaster hosts</em>. Wasps from the <em>Ganaspis</em> genus, <em>G. brasiliensis</em> and <em>G. hookeri</em>, also elicit differential encapsulation responses in wild-type hosts. Larvae expressing the secreted SSp40 protein showed reduced immune competence, and there was a dose-dependent decrease in their encapsulation capacity. This decrease likely resulted from significant clustering and damage to host hemocytes associated with SSp40 expression. Conversely, infection by SSp40 “knockdown” <em>L. heterotoma</em> wasps, obtained using a novel “hairpin feeding” approach, compromised wasp virulence and induced significantly higher encapsulation in wild-type <em>D. melanogaster</em> hosts. These results establish that SSp40 is a bona fide virulence protein and can damage hemocytes in the absence of other venom proteins. Similar cross-clade studies in this natural host-parasitoid system will help discover other key virulence proteins, identify their activities, and redefine the evolutionary relationships among parasitoid wasps.</p>

Name thesis:degree_name

Master of Science (M.S.)

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Biology

Year dc:date.available

2024

Author dc:creator

• Ramsarran, Christina

Contributors dc:contributor

• Shubha Govind
• Yevgeniy Grigoriev
• Rebecca Spokony

• innate immunity
• RNA interference
• host-parasite
• immune suppression
• blood cells
• virulence
• Genetics

Repository record dc:identifier

https://academicworks.cuny.edu/cc_etds_theses/1172

OAI identifier oai:identifier

oai:academicworks.cuny.edu:cc_etds_theses-2247