title: The silkworm glutathione S-transferase gene noppera-bo is required for ecdysteroid biosynthesis and larval development.
abstract: Insect molting and metamorphosis are tightly controlled by ecdysteroids, which are important steroid hormones that are synthesized from dietary sterols in the prothoracic gland. One of the ecdysteroidogenic genes in the fruit fly Drosophila melanogaster is noppera-bo (nobo), also known as GSTe14, which encodes a member of the epsilon class of glutathione S-transferases. In D. melanogaster, nobo plays a crucial role in utilizing cholesterol via regulating its transport and/or metabolism in the prothoracic gland. However, it is still not known whether the orthologs of nobo from other insects are also involved in ecdysteroid biosynthesis via cholesterol transport and/or metabolism in the prothoracic gland. Here we report genetic evidence showing that the silkworm Bombyx mori ortholog of nobo (nobo-Bm; GSTe7) is essential for silkworm development. nobo-Bm is predominantly expressed in the prothoracic gland. To assess the functional importance of nobo-Bm, we generated a B. mori genetic mutant of nobo-Bm using TALEN-mediated genome editing. We show that loss of nobo-Bm function causes larval arrest and a glossy cuticle phenotype, which are rescued by the application of 20-hydroxyecdysone. Moreover, the prothoracic gland cells isolated from the nobo-Bm mutant exhibit an abnormal accumulation of 7-dehydrocholesterol, a cholesterol metabolite. These results suggest that the nobo family of glutathione S-transferases is essential for development and for the regulation of sterol utilization in the prothoracic gland in not only the Diptera but also the Lepidoptera. On the other hand, loss of nobo function mutants of D. melanogaster and B. mori abnormally accumulates different sterols, implying that the sterol utilization in the PG is somewhat different between these two insect species.
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan.
authors.forename: Sora
authors.initials: S
authors.lastname: Enya
authors.affiliation: National Institute of Agrobiological Sciences, Owashi 1-2, Tsukuba, Ibaraki 305-8634, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Daimon
authors.affiliation: Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8562, Japan.
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Igarashi
authors.affiliation: Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8562, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kataoka
authors.affiliation: National Institute of Agrobiological Sciences, Owashi 1-2, Tsukuba, Ibaraki 305-8634, Japan.
authors.forename: Miwa
authors.initials: M
authors.lastname: Uchibori
authors.affiliation: National Institute of Agrobiological Sciences, Owashi 1-2, Tsukuba, Ibaraki 305-8634, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Sezutsu
authors.affiliation: National Institute of Agrobiological Sciences, Owashi 1-2, Tsukuba, Ibaraki 305-8634, Japan.
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Shinoda
authors.affiliation: Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8572, Japan; PRESTO, JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012, Japan. Electronic address: ryusuke-niwa@umin.ac.jp.
authors.forename: Ryusuke
authors.initials: R
authors.lastname: Niwa
mesh_terms: D000818:Animals; D012831:Bombyx / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D003684:Dehydrocholesterols / Q000378:metabolism; D026461:Ecdysteroids / Q000096:biosynthesis*; D004441:Ecdysterone / Q000378:metabolism; D017344:Genes, Insect; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism*; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism*; D007814:Larva / Q000235:genetics / Q000254:growth & development / Q000378:metabolism
chemical_list: D003684:Dehydrocholesterols; D026461:Ecdysteroids; D019476:Insect Proteins; D004441:Ecdysterone; C016705:7-dehydrocholesterol; D005982:Glutathione Transferase
keywords: Bombyx mori; Ecdysteroids; Glutathione S-transferase; Prothoracic gland; Sterol; noppera-bo