title: Chitin synthase B: a midgut-specific gene induced by insect hormones and involved in food intake in Bombyx mori larvae.
abstract: Chitin synthase (CHS) is the key regulatory enzyme in chitin synthesis and excretion in insects, and a specific target of insecticides. We cloned a CHS B gene of Bombyx mori (BmChsB) and showed it to be midgut specific, highly expressed during the feeding process in the larva. Knockdown of BmChsB expression in the third-instar larvae increased the number of nonmolting and abnormally molting larvae. Exposure to nikkomycin Z, a CHS inhibitor, reduced the amount of chitin in the peritrophic membrane of molted larvae, whereas abnormally elevated BmChsB mRNA levels were readily detected from the end of molting and in the newly molted larvae. Exogenous 20-hydroxyecdysone (20E) and methoprene, a juvenile hormone analogue, significantly upregulated the expression of BmChsB when the levels of endogenous molting hormone (MH) were low and the levels of endogenous juvenile hormone (JH) were high immediately after molting. When levels of endogenous MH were high and those of endogenous JH were low during the molting stage, exogenous 20E did not upregulate BmChsB expression and exogenous methoprene upregulated it negligibly. When the endogenous hormone levels were low during the mulberry-leaf intake process, BmChsB expression was upregulated by exogenous methoprene. We conclude that the expression of BmChsB is regulated by insect hormones, and directly affects the chitin-synthesis-dependent form of the peritrophic membrane and protects the food intake and molting process of silkworm larvae.
authors: Department of Applied Biology, School of Biology and Basic Medical Sciences, Medical College, Soochow University, Suzhou, China; National Engineering Laboratory for Modern Silk, Institute of Agricultural Biotechnology & Ecology, Soochow University, Suzhou, China.
authors: Weiwei
authors: W
authors: Zhuo
authors: Feng
authors: F
authors: Chu
authors: Lingfei
authors: L
authors: Kong
authors: Hui
authors: H
authors: Tao
authors: Yanghu
authors: Y
authors: Sima
authors: Shiqing
authors: S
authors: Xu
mesh_terms: D000818:Animals; D001069:Appetite Regulation / Q000235:genetics*; D012831:Bombyx / Q000201:enzymology* / Q000235:genetics*; D002687:Chitin Synthase / Q000235:genetics* / Q000378:metabolism*; D041981:Gastrointestinal Tract / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D007301:Insect Hormones / Q000494:pharmacology; D007814:Larva / Q000201:enzymology / Q000235:genetics; D018978:Molting / Q000235:genetics
chemical_list: D007301:Insect Hormones; D002687:Chitin Synthase
keywords: Bombyx mori; chitin synthase B; exogenous hormone; gene expression; nikkomycin Z