Expression analyses of caspase‐1 and related activities in the midgut of Galleria mellonella during metamorphosis

Abstract

The cDNA encoding caspase-1, a main protease involved in apoptosis, was cloned and sequenced from the midgut of the greater wax moth, Galleria mellonella. The open reading frame contains 879 nucleotides, encodes 293 amino acids, and was registered as Gmcaspase-1. The sequence comparison showed a high homology to lepidopteran caspase-1, human caspase-3, and ced-3 of Caenorhabditis elegans. Gmcaspase-1 is predicted to contain a short prodomain, large subunit, and small subunit domain. It also exhibits all characteristics of caspase, including three conserved cleavage sites after Asp-25, Asp-192, and Asp-181, three active site residues including a highly conserved QACQG pentapeptide active-site motif, and four substrate binding sites. The expression profiles during development showed that the transcript of Gmcaspase-1 and its protein products appeared in two or more waves in the midgut during metamorphosis. Immunohistochemistry, in situ hybridization, and TUNEL analyses revealed that apoptosis occurred first at the basal, then middle and then apical regions in the midgut epithelium and the yellow body is formed in the lumen. At least three waves of mitosis and differentiation follow the apoptosis waves from the basal and middle to apical parts to form the adult epithelium.

Roles and regulation of autophagy and apoptosis in the remodelling of the lepidopteran midgut epithelium during metamorphosis

“…We hypothesize that the presence of two rounds of caspase activation might be necessary for a two-step process in the demise of different midgut regions or cell types (e.g., columnar vs goblet cells). This hypothesis is corroborated by a previous study of the midgut of Galleria mellonella , where three different apoptotic waves were required for degeneration of distinct parts of the midgut epithelium25.…”

“…Autophagy is also required for activating caspase-dependent cell death for removal of the salivary gland and during oocyte maturation3048. Although the functions of autophagy and apoptosis were hypothesized to be tissue-specific in Lepidoptera7892526, functional studies aiming to unravel their roles have never been performed. Our data show that the midgut epithelium of larvae treated with the autophagy inhibitors chloroquine and wortmannin present a more degraded morphology and enhanced levels of caspases.…”

“…A phenomenon that has been widely described in several organs that die during metamorphosis in Lepidoptera is the coexistence of autophagic and apoptotic features357892324252627. This evidence has prompted the hypothesis of a causative role of autophagy in the demise of these tissues, although the existence of autophagic cell death in these insects has never been clearly and definitively demonstrated2128.…”

Legionella pneumophila Pathogenesis in the Galleria mellonella Infection Model

“…Virulence depends on the Dot/Icm T4SS, and bacteria seem to reside and replicate in a typical LCV. Future advances in our knowledge about the G. mellonella immune gene repertoire (50), cell death pathways (25), and hemocyte biology (28,30), together with initiatives to advance RNA interference systems in Lepidoptera spp. (49), will further increase the value of G. mellonella as an infection model which could potentially be used to study the role of Dot/Icm T4SS effectors, the T2SS, and other factors in the virulence of Legionella spp.…”

Rice ragged stunt virus-induced apoptosis affects virus transmission from its insect vector, the brown planthopper to the rice plant

“…We identified five caspase homolog genes through searching the N. lugens genome and transcriptome datasets1819202122. Three genes are highly homologous to each other and share significant sequence similarities with insect caspase-1 genes112324252627. Caspase-1, the first insect caspase to be discovered, was identified in Spodoptera frugiperda 28.…”