Phenol oxidase is a necessary enzyme for the silkworm molting which is regulated by molting hormone.

Insect molting is an important developmental process of metamorphosis, which is initiated by molting hormone. The molting process includes the activation of dermal cells, epidermal cells separation, molting fluid secretion, the formation of new epidermis and old epidermis excoriation etc. Polyphenol oxidases (PPOs), dopa decarboxylase and acetyltransferase are necessary enzymes for this process. Traditionally, the phenol oxidase was considered as an enzyme for epidermal layer's tanning and melanization. This work suggested that polyphenol oxidases are one set of the key enzymes in molting, which closely related with the role of ecdysone in regulation of molting processes. The data showed that the expression peak of phenol oxidase in silkworm is higher during molting stage, and decreases after molting. The significant increase in the ecdysone levels of haemolymph was observed in the artificially fed silkworm larvae with ecdysone hormone. Consistently, the phenol oxidase expression was significantly elevated compared to the control. PPO1 RNAi induced phenol oxidase expression obviously declined in the silkworm larvae, and caused the pupae incomplete pupation. Overall, the results described that the phenol oxidase expression is regulated by the molting hormone, and is a necessary enzyme for the silkworm molting.

Expression and functions of dopa decarboxylase in the silkworm, Bombyx mori was regulated by molting hormone.

Insect molting is an important developmental process of metamorphosis, which is initiated by molting hormone. Molting includes the activation of dermal cells, epidermal cells separation, molting fluid secretion, the formation of new epidermis and old epidermis shed and other series of continuous processes. Polyphenol oxidases, dopa decarboxylase and acetyltransferase are necessary enzymes for this process. Traditionally, the dopa decarboxylase (BmDdc) was considered as an enzyme for epidermal layer's tanning and melanization. This work suggested that dopa decarboxylase is one set of the key enzymes in molting, which closely related with the regulation of ecdysone at the time of biological molting processes. The data showed that the expression peak of dopa decarboxylase in silkworm is higher during molting stage, and decreases after molting. The significant increase in the ecdysone levels of haemolymph was also observed in the artificially fed silkworm larvae with ecdysone hormone. Consistently, the dopa decarboxylase expression was significantly elevated compared to the control. BmDdc RNAi induced dopa decarboxylase expression obviously declined in the silkworm larvae, and caused the pupae appeared no pupation or incomplete pupation. BmDdc was mainly expressed and stored in the peripheral plasma area near the nucleus in BmN cells. In larval, BmDdc was mainly located in the brain and epidermis, which is consisted with its function in sclerotization and melanization. Overall, the results described that the dopa decarboxylase expression is regulated by the molting hormone, and is a necessary enzyme for the silkworm molting.

Characterization of adaptor protein complex-1 in the silkworm, Bombyx mori.

To investigate the function of adaptor protein complex-1 (AP-1) in the silkworm, we characterized AP-1 in the silkworm by RNAi technique and co-localization methods. As a result, AP-1 was found to exist as cytosolic form and membrane-bound form distinguished by phosphate status, showing molecular mass difference. There was relatively more cytosolic form of AP-1 than its membrane-bound counterpart in the silkworm. However, AP-1 distributed predominantly as cytosolic form in BmN cells. Interruption of AP-1 expression via DsRNA was more efficient in BmN cells than in the insect larval, which led to a tendency to dissociation between subcellular organelles like the Golgi apparatus and the mitochondria. Environmental condition changes like relatively higher temperature and treatment with dimethyl sulfoxide can lead to expression variance of AP-1 both in mRNA and protein level. In BmN cells, both the heavy chain γ and light chain σ could clearly co-localize with AP-1 ß, mostly forming pits in cytoplasm. Two isoforms of AP-1 σ corresponded to distinct subcellular distribution pattern, possibly due to C-terminal amino acids difference.

Expression and localization of silkworm adaptor protein complex-1 subunits, which were down-regulated post baculovirus infection.

Adaptor protein complexes (APs) function as vesicle coat components in different membrane traffic pathways. In this study the subunits of adaptor protein complex-1 (AP-1) of silkworm Bombyx mori were molecularly characterized. All coding genes for the four subunits were cloned and sequenced. Phylogenic tree for each adaptin was constructed and all subunits were found to be conserved in respective group among organisms. The mRNA expression pattern for each adaptin was similar among tissues. Alternative splicing event was observed in genes encoding both the heavy chain gamma and beta adaptin and the light chain subunit, which could generate other possible adaptin forms. GFP-tagged fusion proteins indicated that AP-1 located in the peripheral plasma area. Furthermore, the BmNPV infection in B. mori cells had differentiated effect on the expression level of AP-1 subunits.

A transgenic Bm cell line of piggyBac transposon-derived targeting expression of humanized glycoproteins through N-glycosylation.

Glycoproteins have been implicated in a wide variety of important biochemical and biological functions, including protein stability, immune function, enzymatic function, cellular adhesion and others. Unfortunately, there is no therapeutic protein produced in insect system to date, due to the expressed glycoproteins are paucimannosidic N-glycans, rather than the complex, terminally sialylated N-glycans in mammalian cells. In this paper, we cloned the necessary genes in glycosylation of mammalian cells, such as N-acetylglucosaminyltransferase II (Gn-TII), galactosyltransferases (Gal-Ts), 2,6-Sial-T (ST6 GalII)and 2,3-Sial-T (ST3GalIII), and transformed them to silkworm genome of BmN cell line through transgenesis to establish a transgenic Bm cell line of piggyBac transposon-derived targeting expression of humanized glycoproteins. The study supplied a new insect cell line which is practically to produce "bisected" complex N-glycans like in mammalian cells.

Expression pattern of enzymes related to juvenile hormone metabolism in the silkworm, Bombyx mori L.

The physiological balance of juvenile hormone (JH) in insects depends on its biosynthesis and degradation pathway. Three key enzymes namely, juvenile hormone esterase (JHE), juvenile hormone epoxide hydrolase (JHEH) and juvenile hormone diol kinase (JHDK) are required for degradation in insects. Our present results showed that JHE and JHEH exhibited expression in almost all the tissues. This indicated that JHE and JHEH might degrade JH simultaneously. In addition, the highest levels of JHDK were observed in the midgut, with trace level being found in the malpighian tubule and haemocytes. Since the midgut is a digestive organ and not a JH target, it was hypothesized that both JHE and JHEH hydrolyzed JH to JH diol (JHd) which was then transported to midgut and hydrolyzed further by JHDK, to be finally excreted out of the body. Also the expression studies on JH degradation enzymes in different tissues and stages indicated that the activities of the three enzymes are specific and coincident with the JH functions in silkworm, Bombyx mori L.

Cloning and characterization of the Bombyx mori ecdysone oxidase.

The physiological titer of molting hormones in insects depends on relative activities of synthesis and degradation pathways. Ecdysone oxidase (EO) is a key enzyme in the inactivation of ecdysteroid. However, there are only a few reports on ecdysteroid inactivation and its enzymes in silkworm. In this study, we cloned and characterized the Bombyx mori EO (BmEO). The BmEO cDNA contains an ORF of 1,695 bp and the deduced protein sequence contains 564 amino acid residues. The deduced protein sequence contains two functional domains of glucose-methanol-choline oxidoreductase in N-terminal and C-terminal. Comparing the expression levels of BmEO in different tissues, high transcription was mainly present in hemocytes. Reduced expression of this enzyme is expected to lead to pathological accumulation of ecdysone in the hemolymph of silkworm larvae or pupae. Our data show that RNA inference of BmEO transcripts resulted in the accumulation of ecdysteroid and death of larvae or pupae. We infer that EO is a crucial element in the physiology of insect development.

Cloning and expression pattern of 3-dehydroecdysone 3ß-reductase (3DE 3ß-reductase) from the silkworm, Bombyx mori L.

Molting in insects is regulated by molting hormones (ecdysteroids), which are also crucial to insect growth, development, reproduction, etc. Ecdysone was inactivated to 3-dehydroecdysone (3DE) under ecdysone oxidase (EO), and followed by NAD(P)H-dependent irreversible reduction to 3-epiecdysteroid under 3DE 3a-reductase. On the other hand, 3-dehydroecdysone undergoes reversible reduction to ecdysone by 3DE 3ß-reductase in the hemolymph. In this article, we cloned and characterized 3-dehydroecdysone 3ß-reductase (3DE 3ß-reductase) in the different tissues and the developing stage from the silkworm, Bombyx mori L. The B. mori 3DE 3ß-reductase cDNA contains an ORF 972 bp and the deduced protein sequence containing 323 amino acid residues. Analysis showed that the deduced 3DE 3ß-reductase belongs to the aldo-keto reductase (AKR) superfamily, which has the NAD(P)-binding domain, indicating that the function of 3DE 3ß-reductase depends on the existence of NAD(P)H. Using Escherichia coli, a high level expression of a fusion polypeptide band of approx. 40 kDa was observed. The high transcription of 3DE 3ß-reductase was mainly observed in the genitalia and fatty bodies in the third day of the fifth-instar larvae, followed next in the head, epidermis, and hemocytes. The expression of 3DE 3ß-reductase in the early of every instar was lower than that in the late of instar. When the titer of 3DE is low, higher expression of 3DE 3ß-reductase is necessary to maintain the ecdysone titer in body through converting 3DE to ecdysone, while the 3DE titer is high, the expression of 3DE 3ß-reductase showed feedback inhibition.

Construction and application of an electronic spatiotemporal expression profile and gene ontology analysis platform based on the EST database of the silkworm, Bombyx mori.

An Expressed Sequence Tag (EST) is a short sub-sequence of a transcribed cDNA sequence. ESTs represent gene expression and give good clues for gene expression analysis. Based on EST data obtained from NCBI, an EST analysis package was developed (apEST). This tool was programmed for electronic expression, protein annotation and Gene Ontology (GO) category analysis in Bombyx mori (L.) (Lepidoptera: Bombycidae). A total of 245,761 ESTs (as of 01 July 2009) were searched and downloaded in FASTA format, from which information for tissue type, development stage, sex and strain were extracted, classified and summed by running apEST. Then, corresponding distribution profiles were formed after redundant parts had been removed. Gene expression profiles for one tissue of different developmental stages and from one development stage of the different tissues were attained. A housekeeping gene and tissue-and-stage-specific genes were selected by running apEST, contrasting with two other online analysis approaches, microarray-based gene expression profile on SilkDB (BmMDB) and EST profile on NCBI. A spatio-temporal expression profile of catalase run by apEST was then presented as a three-dimensional graph for the intuitive visualization of patterns. A total of 37 query genes confirmed from microarray data and RT-PCR experiments were selected as queries to test apEST. The results had great conformity among three approaches. Nevertheless, there were minor differences between apEST and BmMDB because of the unique items investigated. Therefore, complementary analysis was proposed. Application of apEST also led to the acquisition of corresponding protein annotations for EST datasets and eventually for their functions. The results were presented according to statistical information on protein annotation and Gene Ontology (GO) category. These all verified the reliability of apEST and the operability of this platform. The apEST can also be applied in other species by modifying some parameters and serves as a model for gene expression study for Lepidoptera.

[Structure and expression analysis of cbp gene in different natural colored-cocoon strains of Bombyx mori].

Carotenoid-binding protein (CBP) is the only key protein that has been characterized to be involved in yellow cocoon coloration of the domesticated silkworm (Bombyx mori). Gene structure and mRNA expression profiles of cbp along with UV-Vis spectrum profiles of carotenoids in silk glands were investigated among twelve strains to disclose their relationship with cocoon color. Yellow cocoon strains of B. mori contained two or three cbp gene types, which had different mRNA products with a longer form acting functionally to code CBP protein and the smaller one without exon 2. The structures of cbp were different among the green cocoon strains with the mRNA product lacking exon 2. Only one cbp gene structure existed in white cocoon strains of B. mori, which produced the mRNA product free of exon 2. A newly identified intron 1 sequence of cbp gene in this study may have cocoon color-specificity among strains. The UV-Vis spectrum profiles of carotenoids in the yellow cocoon strains' silk glands were significantly different from those in the green cocoon strains and white cocoon strains.Together, it can be concluded that the gene structure and expression profile of cbp was closely linked to cocoon colors of B. mori.

A transgenic Marc-145 cell line of piggyBac transposon-derived targeting shRNA interference against porcine reproductive and respiratory syndrome virus.

Porcine reproductive and respiratory syndrome (PRRS) is now considered to be one of the most important diseases in countries with intensive swine industries. The two major membrane-associated proteins of porcine reproductive and respiratory syndrome virus (PRRSV), GP5 and M (encoded by ORF5 and ORF6 genes, respectively), are associated as disulfide-linked heterodimers (GP5/M) in the virus particle. In this study, we designed 5 of the small hairpin RNAs (shRNAs) targeting the GP5 and M gene of PRRSV respectively, and investigated their inhibition to the production of PRRSV. The highest activity displayed in shRNAs of the ORF6e sequence (nts 261-279), which the inhibition rate reached was 99.09%. The result suggests that RNAi technology might serve as a potential molecular strategy for PRRSV therapy. Furthermore, the transgenic Marc-145 cell line of piggyBac transposon-derived targeting shRNA interference against PRRS virus was established. It presented stable inhibition to the replication and amplification of PRRS. The work implied that shRNAs targeting the GP5 and M gene of PRRSV may be used as potential RNA vaccines in vivo, and supplied the screening methods of transformed pig embryonic fibroblast which are prerequisite for the disease-resistant transgenic pigs to PRRS.

Molecular cloning and characterization of a putative cDNA encoding endoglucanase IV from Trichoderma viride and its expression in Bombyx mori.

The development of cellulase production technology has greatly contributed to the successful use of cellulosic materials as renewable carbon sources. In this study, a putative endoglucanase IV (EG IV) complementary DNA was cloned from the mycelium of a strain of the filamentous fungus Trichoderma viride using a PCR-based exon-splicing method and expressed in both a silkworm BmN cell line and in silkworm larvae. Western blot analysis detected a band of 42 kDa in BmN cells after infection with a recombinant mBacmid/BmNPV/EG IV baculovirus. Sequence alignment analysis of the T. viride EG IV gene showed two domains that were highly conserved with glycosyl hydrolases and a funga-type cellulose-binding domain. Analysis of variance showed that silkworms infected with recombinant baculoviruses exhibited significantly higher enzyme activity that was 48.84% higher than silkworms infected with blank baculoviruses and 46.61% higher than normal silkworms. The expressed bioactive EG IV was also stable at the pH range from 5.0 to 10.0. The availability of large quantities of bioactive EG IV in silkworm provided a possibility to produce cellulase transgenic silkworm, which express bioactive cellulase specially in its digestive tract and improve its metabolism efficiency of mulberry leaves. Its application in the sericulture industry may be very promising.

Heterologous expression characteristics of Trichoderma viride endoglucanase V in the silkworm, Bombyx mori L.

Efficient degradation of cellulose needs a synergistic reaction of the cellulolytic enzymes, which include exoglucanases, endoglucanases, and ß-1,4-glucosidase. In this study, we used an improved Bac-to-Bac/BmNPV baculovirus expression system, which lacks the virus-encoded chitinase cathepsin (v-cath) genes of Bombyx mori nucleopolyhedrovirus (BmNPV), to express the endoglucanase V (EG V) gene from Trichoderma viride in silkworm BmN cells and silkworm larvae, and analyzed the characteristics of the recombinant enzyme in silkworm larvae. The result showed that an around 36-kDa protein was visualized in BmN cells at 48 h after the second-generation recombinant mBacmid/BmNPV/EG V baculovirus infection. The crude enzyme extract from the recombinant baculoviruses-infected silkworms exhibited a significant maximum activity at the environmental condition of pH 5.0 and a temperature of 50 °C, and increased 39.86% and 37.76% compared with that from blank mBacmid/BmNPV baculovirus-infected silkworms and normal silkworms, respectively. It was stable at pH range from 5.0 to 10.0 and at temperature range from 40 to 60 °C. The availability of large quantities of EG V that the silkworm provides might greatly facilitate the future research and the potential application in industries.