Effects of a Fat Body Extract on Larval Midgut Cells and Growth of Lepidoptera

Abstract

Treatment with fat body extract (FBX) from pupae of the tobacco hornworm, Manduca sexta, caused mortality in larvae of two pest lepidopterans, the gypsy moth, Lymantria dispar, and the cotton leafworm, Spodoptera littoralis. In FBX-treated larvae, the feeding rate was depressed, causing reduced weight gain and then larval death. Their midgut showed formation of multicellular layers of midgut epidermis, indicating stem-cell hyperplasia. Hence, the integument of FBX-treated larvae had a double cuticle, indicating induction of premature molting. But radioimmunoassay measurements confirmed that the amount of ecdysteroids in FBX was too low to be responsible for the molt-inducing effects observed after treatment with FBX. With midgut stem cell cultures in vitro, addition of FBX to the culture medium stimulated cell proliferation and differentiation in a concentration-dependent manner. This effect was compared with those of insect molting hormones, ecdysone and 20-hydroxyecdysone; an ecdysteroid agonist, RH-2485; and a purified protein from FBX (multiplication factor). This article describes the mode of action of FBX and possible interplay between fat body factor(s) and insect hormones in the development and metamorphosis of the insect midgut.

Analysis of gene expression in the midgut of Bombyx mori during the larval molting stage

“…6g) and DMSO did not affect BrdU incorporation as compared with naïve larvae (Additional file 3: Figure S1). These data indicate that 20E injection resulted in DNA synthesis in a few midgut cells in vivo, which is consistent with the observation in vitro [44, 45]. …”

“…Hemolymph 20E peaks at the initiation of the molting stage and decreases gradually thereafter [34, 43]. Ecdysteroids stimulates proliferation and differentiation of midgut stem cells in a concentration-dependent way [44, 45]. Ecdysone and 20E were particularly active in midgut cell proliferation and differentiation, respectively.…”

“…In the silkworm, there are no protein markers for columnar cells and goblet cells, respectively. We tried the tissue culture protocol developed by Smagghe et al [44, 45] and found that the columnar cells and goblet cells in the silkworm larval midguts were very easily broken after being cultured for a while. Thus, it is difficult to differentiate cell proliferation and differentiation in the molting midguts when specific markers to distinguish different midgut cell types are not available.…”

New insights into autophagic cell death in the gypsy moth Lymantria dispar: a proteomic approach

“…This hypothesis is in agreement with the observation that fat body extracts are able to induce premature moulting in the larvae of the gypsy moth L. dispar (Smagghe et al 2003). In both Diptera (Rusten et al 2004) and Lepidoptera (Müller et al 2004), autophagic processes during metamorphosis play a key role in the elimination of larval fat body, and a specific role for autophagic developmental cell death has been shown in Drosophila (Berry and Baehrecke 2007).…”

“…Moreover, treatment of whole larvae of L. dispar with fat body extracts of the tobacco hornworm, Manduca sexta, induces a premature molting, irrespective of the ecdysteroidal content of fat body extracts (Smagghe et al 2003), suggesting that other molecules play a role in these processes. We have therefore decided to examine the effects of a medium conditioned with oligomycin-A-treated IPLB-LdFB cells, in order to assess: (1) whether the medium is able to influence the survival of untreated and apoptotic-competent IPLB-LdFB cells and (2) whether oligomycin A triggers autophagic cell death as a result of specific signalling.…”