title: Transcriptomic analysis of developmental features of Bombyx mori wing disc during metamorphosis.
abstract: BACKGROUND
  Wing discs of B. mori are transformed to pupal wings during the larva-to-pupa metamorphosis with dramatic morphological and structural changes. To understand these changes at a transcriptional level, RNA-seq of the wing discs from 6-day-old fifth instar larvae (L5D6), prepupae (PP) and pupae (P0) was performed.
  
  
  RESULTS
  In total, 12,254 transcripts were obtained from the wing disc, out of which 5,287 were identified to be differentially expressed from L5D6 to PP and from PP to P0. The results of comprehensive analysis of RNA-seq data showed that during larvae-to-pupae metamorphosis, many genes of 20E signaling pathway were up-regulated and those of JH signaling pathway were down-regulated. Seventeen transcription factors were significantly up-regulated. Cuticle protein genes (especially wing cuticle protein genes), were most abundant and significantly up-regulated at P0 stage. Genes responsible for the degradation and de novo synthesis of chitin were significantly up-regulated. There were A and B two types of chitin synthases in B. mori, whereas only chitin synthase A was up-regulated. Both trehalose and D-fructose, which are precursors of chitin synthesis, were detected in the hemolymph of L5D6, PP and P0, suggesting de novo synthesis of chitin. However, most of the genes that are related to early wing disc differentiation were down-regulated.
  
  
  CONCLUSIONS
  Extensive transcriptome and DGE profiling data of wing disc during metamorphosis of silkworm have been generated, which provided comprehensive gene expression information at the transcriptional level. These results implied that during the larva-to-pupa metamorphosis, pupal wing development and transition might be mainly controlled by 20E signaling in B. mori. The 17 up-regulated transcription factors might be involved in wing development. Chitin required for pupal wing development might be generated from both degradation of componential chitin and de novo synthesis. Chitin synthase A might be responsible for the chitin synthesis in the pupal wing, while both trehalose and D-fructose might contribute to the de novo synthesis of chitin during the formation of pupal wing.
authors.forename: Jun
authors.initials: J
authors.lastname: Ou
authors.forename: Hui-Min
authors.initials: HM
authors.lastname: Deng
authors.forename: Si-Chun
authors.initials: SC
authors.lastname: Zheng
authors.forename: Li-Hua
authors.initials: LH
authors.lastname: Huang
authors.affiliation: Laboratory of Molecular and Developmental Entomology, Guangdong Provincial Key Lab of Biotechnology for Plant Development, School of Life Sciences, South China Normal University, Guangzhou 510631, China. qlfeng@scnu.edu.cn.
authors.forename: Qi-Li
authors.initials: QL
authors.lastname: Feng
authors.forename: Lin
authors.initials: L
authors.lastname: Liu
mesh_terms: D000818:Animals; D012831:Bombyx / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development*; D002686:Chitin / Q000378:metabolism; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D019476:Insect Proteins / Q000235:genetics*; D008675:Metamorphosis, Biological; D008969:Molecular Sequence Data; D017423:Sequence Analysis, RNA; D015398:Signal Transduction; D014921:Wings, Animal / Q000254:growth & development* / Q000378:metabolism
chemical_list: D019476:Insect Proteins; C047663:cuticle proteins, insects; D002686:Chitin