Bombyx mori
not annotated - annotated - LINNAEUS only
20825506
Transcription factors BmPOUM2 and BmBetaFTZ-F1 are involved in regulation of the expression of the wing cuticle protein gene BmWCP4 in the silkworm, Bombyx mori.
In Bombyx mori, the wing cuticle protein gene BmWCP4 is expressed specifically in the epidermis at the onset and mid-stage of pupation and is responsible for the formation of the pupal cuticle during the larval-pupal metamorphosis. The gene consists of four exons and three introns and is present as a single copy in the genome. Its expression was up-regulated by 20-hydroxyecdysone (20E) and the 20E-induced expression was suppressed by juvenile hormone (JH) III. The upstream regulatory sequence region of the BmWCP4 gene was cloned and the regulatory elements responsible for 20E induction were identified. Two cis-regulatory elements (CREs) bound by the transcription factors BmPOUM2 and BmBetaFTZ-F1 were identified that mediated 20E-regulated expression of this gene. An electrophoretic mobility shift assay detected two nuclear proteins isolated from the epidermis and the BmN cell line that specifically bound to the POU and BetaFTZ-F1 CREs, respectively. BmPOUM2 recombinant protein explicitly bound to the POU CRE. Developmental and 20E-induced expression of the BmWCP4, BmPOUM2 and BmBetaFTZ-F1 genes showed that BmPOUM2 and BmBetaFTZ-F1 were initially expressed, followed by BmWCP4. These data suggest that the 20E-induced expression of BmWCP4 is mediated by the transcription factors BmPOUM2 and BmBetaFTZ-F1 binding to their CREs in the regulatory sequence region of the BmWCP4 gene.
21091811
Candidate chemosensory ionotropic receptors in a Lepidoptera.
A new family of candidate chemosensory ionotropic receptors (IRs) related to ionotropic glutamate receptors (iGluRs) was recently discovered in Drosophila melanogaster. Through Blast analyses of an expressed sequenced tag library prepared from male antennae of the noctuid moth Spodoptera littoralis, we identified 12 unigenes encoding proteins related to D. melanogaster and Bombyx mori IRs. Their full length sequences were obtained and the analyses of their expression patterns suggest that they were exclusively expressed or clearly enriched in chemosensory organs. The deduced protein sequences were more similar to B. mori and D. melanogaster IRs than to iGluRs and showed considerable variations in the predicted ligand-binding domains; none have the three glutamate-interacting residues found in iGluRs, suggesting different binding specificities. Our data suggest that we identified members of the insect IR chemosensory receptor family in S. littoralis and we report here the first demonstration of IR expression in Lepidoptera.
21118326
Molecular structure of the prothoracicotropic hormone gene in the northern house mosquito, Culex pipiens, and its expression analysis in association with diapause and blood feeding.
We cloned the gene that encodes prothoracicotropic hormone (PTTH) in the northern house mosquito, Culex pipiens, and investigated its expression profile in short-day (diapause-destined) and long-day (nondiapause-destined) individuals from the fourth-instar larval stage to 2 months of adulthood, as well as after a blood meal. The deduced C. pipiens PTTH (Cupip-PTTH) amino acid sequence contains seven cysteines with a specific spacing pattern. Sequence alignment suggests that Cupip-PTTH is 23% identical to Drosophila melanogaster PTTH, but is >=59% identical to the PTTHs of other mosquitoes. Cupip-PTTH has structural characteristics similar to those of Bombyx mori PTTH and some vertebrate nerve growth factors with cysteine-knot motifs. PTTH transcripts exhibit a daily cycling profile during the final (fourth) larval instar, with peak abundance occurring late in the scotophase. The fourth-larval instar stage is one day longer in short-day larvae than in long-day larvae, resulting in larger larvae and adults. This additional day of larval development is associated with one extra PTTH cycle. No cycling was observed in pupae, but PTTH transcripts were slightly higher in short-day pupae than in long-day pupae throughout much of the pupal stage. PTTH expression persisted at a nearly constant level in diapausing adult females for the first month but then dropped by -50%, while expression decreased at the beginning of adulthood in nondiapausing females and then remained at a low level as long as the females were denied a blood meal. However, when nondiapausing females were offered a blood meal, PTTH transcripts rose approximately 7 fold in 2 h and remained elevated for 24 h. A few diapausing females (-10%) will take a blood meal when placed in close proximity to a host, but much of the blood is ejected and such meals do not result in mature eggs. Yet, elevated PTTH mRNA expression was also observed in diapausing females that were force fed. Our results thus point to several distinctions in PTTH expression between short-day and long-day mosquitoes, but both types of females responded to a blood meal by elevating levels of PTTH mRNA.
21199020
Genetic analysis of the xenobiotic resistance-associated ABC gene subfamilies of the Lepidoptera.
Some ATP-binding cassette (ABC) transporters of subfamilies B, C and G confer resistance to xenobiotics including insecticides. We identified genes of these subfamilies expressed by the lepidopterans Trichoplusia ni and Bombyx mori. The B. mori genome includes eight, six and 13 ABC-B, -C and -G genes, respectively, which encode P-glycoprotein, multidrug resistance protein, MRP, and breast cancer resistance protein, BCRP, homologues. Among the ABC-C and -G subfamilies, gene duplication contributes to protein diversity. We have identified three ABC-B and two ABC-C T. ni genes. Analyses of the T. ni MRP (TrnMRP) revealed unique features, including the potential for TrnMRP4 hyperglycosylation and the alternative splicing of TrnMRP1. Taken together, these attributes of moth multidrug resistance-associated ABCs may confer distinct functional capacities to xenobiotic efflux.
21521139
A review of the implications of heterozygosity and inbreeding on germplasm biodiversity and its conservation in the silkworm, Bombyx mori.
Abstract Silkworm genebanks assume paramount importance as the reservoirs of biodiversity and source of alleles that can be easily retrieved for genetic enhancement of popular breeds. More than 4000 Bombyx mori L (Lepidoptera: Bombycidae) strains are currently available and these strains are maintained through continuous sibling mating. This repeated sibling mating makes the populations of each strain more homozygous, but leads to loss of unique and valuable genes through the process of inbreeding depression. Hence, it is essential to maintain a minimal degree of heterozygosity within the population of each silkworm strain, especially in the traditional geographic strains, to avoid such loss. As a result, accurate estimation of genetic diversity is becoming more important in silkworm genetic resources conservation. Application of molecular markers help estimate genetic diversity much more accurately than that of morphological traits. Since a minimal amount of heterozygosity in each silkworm strain is essential for better conservation by avoiding inbreeding depression, this article overviews both theoretical and practical importance of heterozygosity together with impacts of inbreeding depression and the merits and demerits of neutral molecular markers for measurements of both heterozygosity and inbreeding depression in the silkworm Bombyx mori.
21435060
Characterization of an omega-class glutathione S-transferase in the stress response of the silkmoth.
The glutathione S-transferase (GST) superfamily is involved in detoxification of various xenobiotics. Using real-time PCR, mRNA encoding an omega-class GST of Bombyx mori (bmGSTO) was shown to be induced after exposure to various environmental stresses. A soluble form of recombinant protein (rbmGSTO) was functionally overexpressed in Escherichia coli cells and purified to homogeneity. Cys 38 and Pro 39 were found to be highly conserved in omega-class GSTs, and their roles were investigated by site-directed mutagenesis/kinetic analysis. Mutations of Cys 38 and Pro 39 residues affected the catalytic efficiency of enzymes, indicating that the presence of Cys 38 and Pro 39 residues is important for bmGSTO activity. Thus, bmGSTO could contribute to increasing the environmental stress resistance of lepidopteran insects.
21793956
Identification and expression analysis of nervous wreck, which is preferentially expressed in the brain of the male silkworm moth, Bombyx mori.
Sexually dimorphic neural circuits are essential for reproductive behaviour. The molecular basis of sexual dimorphism in the silkworm moth (Bombyx mori) brain, however, is unclear. We conducted cDNA subtraction screening and identified nervous wreck (Bmnwk), a synaptic growth regulatory gene, whose expression is higher in the male brain than in the female brain of the silkworm. Bmnwk was preferentially expressed in the brain at the late pupae and adult stages. In situ hybridization revealed that Bmnwk is highly expressed in the optic lobe of the male moth brain. These findings suggest that Bmnwk has a role in the development and/or maintenance of the optic lobe in the male silkworm brain.