Analysis of gene expression in the midgut of Bombyx mori during the larval molting stage.
Insects can be models for understanding human intestinal infection and pathology. Molting, a special period during which the old insect cuticle is shed and a new one is produced, is crucial for insect development. Holometabolous insects may experience several larva-to-larva moltings to become larger, a pupal molt and adult eclosion to become adults. During the larval molts, they stop feeding and become quiescent. Although the molting larvae become quiescent, it is not known if changes in microbiome, physiology, development and immunity of midguts occur.



Transcriptome analysis indicated that functions such as metabolism, digestion, and transport may become reduced due to the downregulated expression of many associated genes. During the molting stage, midguts harbor less microflora and DNA synthesis decreases. Both ecdysone and juvenile hormone in the larval midgut likely degrade after entering the larva-to-larva molting stage. However, at 12 h after ecdysis, the feeding larvae of 5th instars that were injected with 20-hydroxyecdysone entered a molting-like stage, during which changes in midgut morphology, DNA synthesis, gene expression, and microflora exhibited the same patterns as observed in the actual molting state.



This study is important for understanding insect midgut physiology, development and immunity during a special development stage when no food is ingested. Although the molting larva becomes immobile and quiescent, we demonstrate that numerous changes occur in midgut morphology, physiology, metabolism and microbiome during this period.
Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China.
Bing
B
Yang
Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China.
Wuren
W
Huang
Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China.
Jie
J
Zhang
Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China.
Qiuyun
Q
Xu
Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China.
Shoulin
S
Zhu
Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China.
Qiaoli
Q
Zhang
Veterinary Pathobiology, University of Missouri, Columbia, MO, 65211, USA.
Brenda T
BT
Beerntsen
College of Life Sciences, Shanghai University, Shanghai, 200444, China. hssong@staff.shu.edu.cn.
Hongsheng
H
Song
Key Laboratory of Insect Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, 200032, China. erjunling@sippe.ac.cn.
Erjun
E
Ling
D000818:Animals; D001692:Biological Transport; D012831:Bombyx / Q000235:genetics* / Q000254:growth & development*; D016000:Cluster Analysis; D004064:Digestive System / Q000378:metabolism*; D004734:Energy Metabolism; D000069196:Gastrointestinal Microbiome; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D007814:Larva; D008018:Life Cycle Stages; D018978:Molting / Q000235:genetics*; D059467:Transcriptome
Larva-to-larva molting; Microarray; Microflora; Midgut