Differentiation of lepidoptera scale cells from epidermal stem cells followed by ecdysone-regulated DNA duplication and scale secreting

Abstract

Integuments are the first line to protect insects from physical damage and pathogenic infection. In lepidopteran insects, they undergo distinct morphology changes such as scale formation during metamorphosis. However, we know little about integument development and scale formation during this stage. Here, we use the silkworm, Bombyx mori, as a model and show that stem cells in the integument of each segment, but not intersegmental membrane, divide into two scale precursor cells during the spinning stage. In young pupae, the scale precursor cell divides again. One of the daughter cells becomes a mature scale-secreting cell that undergoes several rounds of DNA duplication and the other daughter cell undergoes apoptosis later on. This scale precursor cell division is crucial to the development and differentiation of scale-secreting cells because scale production can be blocked after treatment with the cell division inhibitor paclitaxel. Subsequently, the growth of scale-secreting cells is under the control of 20-hydroxyecdysone but not juvenile hormone since injection of 20-hydroxyecdysone inhibited scale formation. Further work demonstrated that 20-hydroxyecdysone injection inhibits DNA duplication in scale-secreting cells while the expression of scale-forming gene ASH1 was down-regulated by BR-C Z2. Therefore, this research demonstrates that the scale cells of the silkworm develops through stem cell division prior to pupation and then another wave of cell division differentiates these cells into scale secreting cells soon after entrance into the pupal stage. Additionally, DNA duplication and scale production in the scale-secreting cells were found to be under the regulation of 20-hydroxyecdysone.

Concordance of the spectral properties of dorsal wing scales with the phylogeographic structure of European male Polyommatus icarus butterflies

“…As already mentioned in the Introduction, the scale formation takes place during the pupal stage and each scale develops individually from scale progenitor cells 62 , the Lycaenidae scales in the lower layer, called ground scales, in general have a simpler structure constituted of the network of ridges, cross-ribs and trabeculae and they contain melanin, a broad band absorber in the UV–Vis range. Melanin is responsible for the brown coloration of these scales.…”

Involvement of Epidermis Cell Proliferation in Defense Against Beauveria bassiana Infection

“…After the fixed-site infection, silkworm larvae, including naïve ones, were injected with 5-Bromo-2′-deoxyuridine (BrdU, Sigma, 19-160) at 10 µl/g body weight to label DNA duplication in epidermis cells for three hours ( 17 ). The primary antibody against BrdU (Sigma, B8434; 1:1000) was utilized to label cells that had incorporated BrdU as described in detail ( 17 , 18 ). The antibody against Phospho-Histone H3 (PH3, Merck, H0412; 1:1000) was used to detect cells that were dividing ( 17 ).…”

“…The primary antibody against BrdU (Sigma, B8434; 1:1000) was utilized to label cells that had incorporated BrdU as described in detail ( 17 , 18 ). The antibody against Phospho-Histone H3 (PH3, Merck, H0412; 1:1000) was used to detect cells that were dividing ( 17 ). The secondary antibody conjugated with Alexa Fluor-488 or Alexa Fluor-594 was utilized and DAPI was used to counter-stain nuclei.…”

“…After entering the 5th larval stage, no DNA duplication and cell division were detected in epidermis cells ( 17 ). DNA duplicates in the midgut cells during 4th larval stage.…”

Analysis of the functions of the signal peptidase complex in the midgut of Tribolium castaneum

“…The goat anti‐rabbit Alexa 488 or goat anti‐rabbit Alexa 594 (1:1000; Invitrogen) conjugated IgG was used as the second antibody. Bromodeoxyuridine (5‐bromo‐2‐deoxyuridine, BrdU) was injected into insects as described elsewhere (Ling et al., ; Yuan et al., ). Mouse anti‐BrdU (1:200; GE Healthcare, Chicago, IL) was used as the primary antibody to detect BrdU.…”