Two Tor genes in the silkworm Bombyx mori

Abstract

Target of rapamycin (TOR), a member of the phosphatidylinositol kinase-related kinase family, plays a critical role in the regulation of growth, metabolism, development and survival, at both the cellular and the organismal levels. Two paralogous Tor genes, BmTor1 and BmTor2, were identified as a pair of inverted repeats in the genome of the silkworm Bombyx mori. The synteny of BmTor1 and CG8360 indicates that BmTor1 is the orthologue while BmTor2 is a duplicate. Analyses of the two BmTor genes at both the nucleotide and amino acid levels reveal that they are evolutionally and structurally conserved. The two BmTor genes had similar expression patterns of tissue distribution with highest levels in the nervous system, and nearly identical developmental change profiles with maximal levels during the 4(th) -larval-moulting and the larval-pupal transition stages. Furthermore, both BmTor genes were up-regulated by either starvation or the moulting hormone 20-hydroxyecdysone (20E), while BmTor2 was more sensitive to both treatments than BmTor1. For the first time, we have identified two copies of the Tor gene in a higher eukaryote, which are induced by starvation and 20E during the larval moulting and the larval-pupal transition stage.

Ras1CA overexpression in the posterior silk gland improves silk yield

“…In addition to the canonical IIS pathway, the TORC1 pathway promotes cell growth through its action on translational initiation, ribosome biogenesis, and nutrient storage [25,26]. Although little is known about the IIS-TORC1 pathways in Bombyx [16,27], Ras activation significantly enhanced the phosphorylation levels of Akt, S6K and 4EBP ( Figure 3C) and positively affected cell size in the posterior silk gland (Figure 2A; Supplementary information, Figure S3). Optical microscopy revealed that cell size in the posterior silk gland of [D(+)E(+)] silkworms was significantly increased with enlarged nuclei ( Figure 5A and 5A'; Supplementary information, Figure S5).…”

TOR signaling is involved in PTTH-stimulated ecdysteroidogenesis by prothoracic glands in the silkworm, Bombyx mori

“…In B. mori, insulin/PI3K/Akt signaling is involved in prothoracic gland ecdysteroidogenesis (Gu et al, 2009). TOR gene transcription appears to be nutrientsensitive: starvation upregulates gene expressions of both TOR1 and TOR2 (Zhou et al, 2010). In addition, when Drosophila larvae are starved, a delay in the transition from the larva to pupa occurs.…”

Guidelines for the use and interpretation of assays for monitoring autophagy

“…452,830,832 Systematic cloning and analysis revealed that homologs of most of the Atg genes identified in other insect species such as Drosophila are present in B. mori, and 11 Atg genes have now been identified in the silkworm genome, as well as other genes involved in the MTOR signal transduction pathway. 833,834 Variations in the expression of several of these genes have been monitored not only in silkworm larval organs, where autophagy is associated with development, 452,[833][834][835] but also in the fat body of larvae undergoing starvation. 833 In the IPLB-LdFB cell line, derived from the fat body of the caterpillar of the gypsy moth Lymantria dispar, indirect immunofluorescence experiments have demonstrated an increased number of Atg8-positive dots in cells with increased autophagic activity; however, western blotting did not reveal the conversion of Atg8 into Atg8-PE.…”

“…833,834 Variations in the expression of several of these genes have been monitored not only in silkworm larval organs, where autophagy is associated with development, 452,[833][834][835] but also in the fat body of larvae undergoing starvation. 833 In the IPLB-LdFB cell line, derived from the fat body of the caterpillar of the gypsy moth Lymantria dispar, indirect immunofluorescence experiments have demonstrated an increased number of Atg8-positive dots in cells with increased autophagic activity; however, western blotting did not reveal the conversion of Atg8 into Atg8-PE. Instead, a single band with an approximate molecular mass of 42 kDa was observed that was independent of the percentage of cells displaying punctate Atg8 (Malagoli D, unpublished results).…”