Upregulation ofAtg5andAIFgene expression in synchronization with programmed cellular death events in integumental epithelium ofBombyx moriinduced by a dipteran parasitoid infection

Abstract

Infection of the commercially important silkworm, Bombyx mori by a tachnid parasitoid, Exorista bombycis induced activation of genes and cellular responses associated with apoptosis in integumental epithelial cells. Composite cellular profile showed initial autophagy, intermediate endoplasmic reticulum degranulation and deformed nucleus as well as later DNA fragmentation indicating apoptosis. Two cell death-associated proteins, autophagy 5-like (Atg5L) and apoptosis-inducing factor (AIF), in addition to caspase, are identified from the infected integumental epithelium through mass spectrometric analysis. Genes encoding these proteins showed age-dependent activation after the infection as revealed by quantitative expression analysis. Atg5 showed early upregulation in association with signs of autophagy whereas AIF showed late upregulation in association with DNA condensation and fragmentation. Expression of AIF showed negative correlation with that of Atg5 after the infection. On the other hand, in control, caspase expression showed positive correlation with AIF expression indicative of regulated expression in normal larval epithelium, which was absent after infection. Activation of Atg5, AIF and caspase genes in close association with different cell death events revealed the synchronized differential expression of apoptosis-associated genes in response to the macroparasitism. Enhanced expression of Atg5, AIF and caspase genes coupled with the appearance of cell death symptoms indicate parasitism-induced activation of genetic machinery to modulate cell death events in the epithelium, which was hither to unknown in invertebrate systems.

MOLECULAR CHARACTERIZATION OF AUTOPHAGY‐RELATED GENE 5 FROM Spodoptera exigua AND EXPRESSION ANALYSIS UNDER VARIOUS STRESS CONDITIONS

“…Atg5 expression was upregulated in integumental epithelium of B. mori induced by a dipteran parasitoid infection (Anitha et al., ). It was also required for survival of Tenebrio molitor against an intracellular pathogen, Listeria monocytogenes (Tindwa et al., ).…”

Phylogeny of Host Response Proteins Activated in Silkworm Bombyx mori in Response to Infestation by Dipteran Endoparasitoid Revealed Functional Divergence and Temporal Molecular Adaptive Evolution

“…Rearing of the silkworm, B. mori, infestation by E. bombycis and collection of integument, haemolymph and hemocyte samples were carried out as described earlier [11][12][13] and briefed here. Protein samples were extracted from integument using total protein extraction reagent (T-PER; Pierce).…”

“…In B. mori, genes encoding the host-response proteins showed differential expression after the parasitic invasion [11][12][13]. Few immune genes showed regulated expression in control larvae which was deregulated due to the parasitic maggot infestation (Table 5).…”

“…Our recent studies showed differential production of host-response proteins, upregulation of associated genes and activation of immunocompetence in B. mori induced by the infestation [11]. The host-response proteins comprised of stress proteins, cytokines, Toll-pathway components, proteolytic enzymes, apoptosis -associated proteins and melanisation pathway components [12,13]. Genome-wide analysis showed that some of the immune proteins are paralogous [4,14] however structural differences indicated that the genes encoding them might have originated from a common ancestor by duplication or as splice variants [4] under different types of selection pressure [15].…”

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

“…Immediately after hatching, neonate parasitoid larvae invade the host larva and continue development as endoparasitoids. Parasitization leads to several organismal effects including reduced body weight and silk production (Narayanaswamy & Devaiah, ) and to immune reactions and apoptosis in the integument (Anitha, Pradeep, & Sivaprasad, ; Pradeep, Anitha, Awasthi, Babu, & Geetha, ). Although parasitoid larvae are encapsulated and melanized, B. mori larva did not curtail the parasitoid effects.…”