title: Ecdysteroid-induced programmed cell death is essential for sex-specific wing degeneration of the wingless-female winter moth.
abstract: The winter moth, Nyssiodes lefuarius, has a unique life history in that adults appear during early spring after a long pupal diapause from summer to winter. The moth exhibits striking sexual dimorphism in wing form; males have functional wings of normal size, whereas females lack wings. We previously found that cell death of the pupal epithelium of females appears to display condensed chromatin within phagocytes. To provide additional detailed data for interpreting the role of cell death, we performed light microscopy, transmission electron microscopy, and TUNEL assay. We consequently detected two modes of cell death, i.e., dying cells showed both DNA fragmentation derived from epithelial nuclei and autophagic vacuole formation. To elucidate the switching mechanism of sex-specific wing degeneration in females of N. lefuarius, we tested the effects of the steroid hormone 20-hydroxyecdysone (20E) on pupal diapause termination and wing morphogenesis in both sexes. When 20E (5.4 µg) was injected into both sexes within 2 days of pupation, wing degeneration started 4 days after 20E injection in females, whereas wing morphogenesis and scale formation started 6 days after 20E injection in males. We discuss two important findings: (1) degeneration of the pupal wing epithelium of females was not only due to apoptosis and phagocytotic activation but also to autophagy and epithelial cell shrinkage; and (2) 20E terminated the summer diapause of pupae, and triggered selective programmed cell death only of the female-pupal wing epithelium in the wingless female winter moth.
authors.affiliation: Department of Life Science, International Christian University, Tokyo, Japan ; Department of Biological Sciences, Tokyo Metropolitan University, Hachioji, Japan.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Niitsu
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
authors.forename: Kouhei
authors.initials: K
authors.lastname: Toga
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, Japan ; Sugadaira Montane Research Center, University of Tsukuba, Sugadaira Kogen, Ueda, Nagano, Japan.
authors.forename: Shigekazu
authors.initials: S
authors.lastname: Tomizuka
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, Toyama, Japan.
authors.forename: Kiyoto
authors.initials: K
authors.lastname: Maekawa
authors.affiliation: Sugadaira Montane Research Center, University of Tsukuba, Sugadaira Kogen, Ueda, Nagano, Japan.
authors.forename: Ryuichiro
authors.initials: R
authors.lastname: Machida
authors.affiliation: Department of Life Science, International Christian University, Tokyo, Japan.
authors.forename: Takehiko
authors.initials: T
authors.lastname: Kamito
mesh_terms: D000165:Acridine Orange; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D053938:DNA Fragmentation; D004441:Ecdysterone / Q000494:pharmacology*; D005260:Female; D020287:In Situ Nick-End Labeling; D008675:Metamorphosis, Biological / Q000502:physiology*; D046529:Microscopy, Electron, Transmission; D009024:Morphogenesis / Q000187:drug effects*; D009036:Moths / Q000502:physiology*; D011679:Pupa / Q000187:drug effects / Q000254:growth & development; D012727:Sex Characteristics; D014921:Wings, Animal / Q000187:drug effects / Q000254:growth & development* / Q000648:ultrastructure
chemical_list: D004441:Ecdysterone; D000165:Acridine Orange