The dipteran parasitoid Exorista bombycis induces pro‐ and anti‐oxidative reactions in the silkworm Bombyx mori: Enzymatic and genetic analysis

Abstract

Hymenopteran parasitoids inject various factors including polydnaviruses along with their eggs into their host insects that suppress host immunity reactions to the eggs and larvae. Less is known about the mechanisms evolved in dipteran parasitoids that suppress host immunity. Here we report that the dipteran, Exorista bombycis, parasitization leads to pro-oxidative reactions and activation of anti-oxidative enzymes in the silkworm Bombyx mori larva. We recorded increased activity of oxidase, superoxide dismutase, thioredoxin peroxidase, catalase, glutathione-S-transferase (GST), and peroxidases in the hemolymph plasma, hemocytes, and fat body collected from B. mori after E. bombycis parasitization. Microarray and qPCR showed differential expression of genes encoding pro- and anti-oxidant enzymes in the hemocytes. The significance of this work lies in increased understanding of dipteran parasitoid biology.

Effect of Tachinid Parasitoid Exorista japonica on the Larval Development and Pupation of the Host Silkworm Bombyx mori

“…One cellular immune reaction against invading parasitoid eggs and larvae is encapsulation with hemocytes followed by melanization ( Yamashita et al, 2019 ; Yang et al, 2021 ). Recent studies identified enhanced expression of innate immunity components of toll and melanization pathways, cytokines or proteolytic enzymes, and oxidative reactions in B. mori following Exorista sorbillans parasitoidism ( Pradeep et al, 2013 ; Anitha et al, 2014 ; Jayaram et al, 2014 ; Makwana et al, 2017 ; Pooja et al, 2017 ; Xu et al, 2019 ). We showed here that around 35% parasitized larvae have undergone successful larval–pupal transition and around 25% of the successful pupated parasitized hosts could eliminate tachinid larvae either in larval or pupal stage and undergo successful eclosion.…”

Dipteran endoparasitoid Exorista bombycis utilizes antihemocyte components against host defense of silkworm Bombyx mori

“…A 25 μl reaction mixture contained 2.5 μl cDNA template, 1 pmol each of the forward and reverse primers, and 12.5 μl SYBR Green qPCR master mix (1×) containing 5 mM MgCl 2. The thermal program used was given as early (Makwana et al, 2017). Gene encoding ribosomal protein S5 from B. mori (NM_001043794) was used as a housekeeping gene that showed consistent expression in different tissues (Butte et al, 2001) and hemocyte samples used in this study.…”

“…A 25 μl reaction mixture contained 2.5 μl cDNA template, 1 pmol each of the forward and reverse primers, and 12.5 μl SYBR Green qPCR master mix (1×) containing 5 mM MgCl 2. The thermal program used was given as early (Makwana et al, 2017).…”

“…On invasion, the parasitoid larva utilizes host larval tissue for survival. However, humoral and cell‐mediated immunity as well as antioxidation reactions are induced in B. mori and other insect systems after parasite invasion (Eleftherianos et al, 2021; Makwana et al, 2017). Parasite invasion induced degranulation in different insect species in association with encapsulation.…”

Comparative Proteomic Analysis Reveals Immune Competence in Hemolymph of Bombyx mori Pupa Parasitized by Silkworm Maggot Exorista sorbillans

“…mori [10]. In the early stage of parasitization, the antioxidative enzyme levels are maintained at a high level in silkworm hemocytes, revealing the continuous need for antioxidative enzymes to prevent immune suppression by enduring parasitism in the host [11]. Under parasitic influence, the expressions of cell apoptosis-associated genes, including autophagy 5-like ( Atg5 ), apoptosis-inducing factor ( AIF ), and nedd2-like caspase, are enhanced in the larval integument of B .…”