Proliferative and preparative cell divisions in wing discs of the last larval instar are regulated by different hormones and determine the size and differentiation of the wing of Bombyx mori. (March 2023)

• Record Type: Journal Article
• Authors: Kawasaki, Hideki; Shahin, Rima; Fujimoto, Shota
• Is Part Of: Journal of insect physiology. Volume 145(2023)
• Publication Date: 2023-03
• Subjects: Insulin -- Ecdysone -- Wing disc -- Bombyx mori -- Metamorphosis -- Cell division; Insects -- Physiology -- Periodicals; Insectes -- Physiologie -- Périodiques; Insects -- Physiology; Periodicals; 571.157
• DOI: 10.1016/j.jinsphys.2023.104476
• Languages: English
• ISSNs: 0022-1910

Abstract

Graphical abstract: Highlights: Two rapid cell division stages exist in wing discs of 5th larval instar of B. mori. Insulin and ecdysone induce the cell division through upregulation of Myc. PI3K/TOR cascades function throughout the 5th larval instar. MMP genes upregulated by 20E downregulated by the addition of Myc or Wnt inhibitor. Cell division at feeding stage is for growth, at spinning stage is for differentiation. Abstract: Through investigating the two different enhanced cell division stages, we tried to clarify the switch from the growth to differentiation in the wing disc of the last larval instar of Bombyx mori . The response to insulin and 20E in vitro was stage specific. Bmmyc expression in V1 wing discs showed differences after being cultured with and without insulin. Bmmyc expression in V5 wing discs also showed differences after being cultured with and without 20E. Cell cycle–related genes, BmE2F1 and BmcycE, were upregulated with insulin or 20E in cultured wing discs of V1 or V5, respectively. Bmwnt1 and Bmras1 showed upregulation with 20E in cultured wing discs. Bmwnt1 showed upregulation with insulin in cultured wing discs, but Bmras1 did not show clear upregulation with insulin treatment. In contrast, Bmdpp showed upregulation with insulin, but did not show clear upregulation with 20E. The addition of PI3K or TOR inhibitors inhibited the upregulation of Bmmyc expression that was upregulated with insulin or 20E. The upregulation of Bmmyc and Bmwnt1 with insulin or 20E was inhibited with the addition of Myc or Wnt inhibitors, respectively. Genes related to matrix metalloprotease showed upregulation with 20E, and the upregulation was inhibited by the addition of Myc or Wnt inhibitors. From the present results, we concluded that cell division during the feeding stage occurred through PI3K/TOR cascade, and that at the wandering stage occurred through ecdysone and PI3K/TOR cascade; the former is for growth and the latter for differentiation.