Effect of oxidative phosphorylation signaling pathway on silkworm midgut following exposure to phoxim.

Organophosphate pesticides are applied widely in the world for agricultural purposes, and their exposures often resulted in non-cocooning of Bombyx mori in China. Silkworm midgut is the major organ for digestion and nutrient absorption, importantly it is also a barrier against foreign substances and chemical pesticides. The purpose of this study was to determine the mechanism of oxidative injury in silkworm midgut with phoxim induction. The results showed that the transcription level of oxidative phosphorylation signaling pathway genes of midgut under phoxim stress. Digital gene expression (DGE) analysis revealed that 24 electron transport chain (ETC)-related genes were upregulated. Quantitative real time polymerase chain reaction results indicated that the ETC the genes encoding NADH-CoQ1, Succinic-Q, cyt c reductase-S, cyt c oxidase-S, cytochrome c oxidase polypeptide IV, ATP synthase, and vacuolar H+ ATP synthase were all significantly up-regulated by 1.50-, 1.31-, 1.42-, 1.44-, 1.70-, 2.03- and 1.43-fold, respectively. Phoxim induction enhanced the activity of ETC complex in mitochondria, and induced the accumulation of ROS in midgut. These results indicated that trace phoxim enhanced respiration in midgut, and the imbalance between the activity changes of ETC may led to reactive oxygen species accumulation. The ETC of mitochondria may be potential biomarkers of midgut toxicity in B. mori caused by phoxim exposure. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 167-175, 2017.

CONSTRUCTION OF SILKWORM MIDGUT cDNA LIBRARY FOR SCREEN AND SEQUENCE ANALYSIS OF PERITROPHIC MEMBRANE PROTEIN GENES.

Silkworm is an important economic insect and the model species for Lepidoptera. The midgut of silkworm is an important physiological barrier, as its peritrophic membrane (PM) can resist pathogen invasion. In this study, a silkworm midgut cDNA library was constructed in order to identify silkworm PM genes. The capacity of the initial library was 6.92 × 10(6) pfu/ml, along with a recombination rate of 92.14% and a postamplification titer of 4.10 × 10(9) pfu/ml. Three silkworm PM protein genes were obtained by immunoscreening, two of which were chitin-binding protein (CBP) genes and one of which was a chitin deacetylase (CDA) gene as revealed by sequence analysis. Three genes were named BmCBP02, BmCBP13, and BmCDA17, and their ORF sizes are 678, 1,029, and 645 bp, respectively; all of them contain sequences of chitin-binding domains. Phylogenetic analysis indicated that BmCBP02 has the highest consensus with Mamestra configurata CBP at 61.0%; BmCBP13 has the highest consensus with Loxostege sticticalis PM CBP at 53.35%; BmCDA17 has the highest consensus with Helicoverpa armigera CDA5a at 70.83%. Tissue transcriptional analysis revealed that all three genes were specifically expressed in the midgut, and during the developmental process of fifth-instar silkworms, the transcription of all the genes showed an upward trend. This study laid a foundation for further studies on the functions of silkworm PM genes.

EXPRESSION AND EFFECTS OF MUTANT Bombyx mori ACETYLCHOLINESTRASE1 IN BmN CELLS.

The main mechanism of toxicity of organophosphate (OP) and carbamate (CB) insecticides is their irreversible binding and inhibition of acetylcholinestrase (AChE), encoded by ace1 (acetylcholinestrase gene 1), leading to eventual death of insects. Mutations in AChE may significantly reduce insects susceptibility to these pesticides. Bombyx mori is an important beneficial insect, and no OP- or CB-resistant strains have been generated. In this study, wild-type ace1 (wace1) and mutant ace1 (mace1) were introduced into BmN cells, confirmed by screening and identification. The expression of wace1 and mace1 in the cells was confirmed by Western blot and their expression levels were about 21-fold higher than the endogenous ace1 level. The activities of AChE in wace1 and mace1 transgenic cells were 10.6 and 20.2% higher compared to control cells, respectively. mace1 transgenic cells had higher remaining activity than wace1 transgenic cells under the treatment of physostigmine (a reversible cholinesterase inhibitor) and phoxim (an OP acaricide). The results showed that ace1 transgene can significantly improve ace1 expression, and ace1 mutation at a specific site can reduce the sensitivity to AChE inhibitors. Our study provides a new direction for the exploration of the relationship between AChE mutations and drug resistance.

Promoter analysis and RNA interference of CYP6ab4 in the silkworm Bombyx mori.

In insects, cytochrome P450 monooxygenases (P450s) are involved in the metabolism of endogenous compounds such as steroid hormones and lipids. In this study, we measured the 20-hydroxyecdysone (20E)-induced transcriptional level of the CYP6ab4 gene using reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR) with a dual spike-in strategy. We then probed possible physiological functions using RNAi experiments in the silkworm Bombyx mori. The activity of the CYP6ab4 promoter in various silkworm tissues was measured by firefly luciferase activity and normalized by Renilla luciferase activity. Our results showed that the activity of the CYP6ab4 promoter was highest in the malpighian tubule, followed by the fat body, the silk gland, the midgut, the epidermis, and the hemocyte. The essential region for basal and 20E-induced transcriptional activity was between -908 and -456 bp from the transcription start site. Through promoter truncation analysis using a dual-luciferase reporter assay in B. mori ovary cells (BmN), we showed that the region between -827 and -722 bp was essential for basal and 20E-induced transcriptional activity. Sequence analysis of this region revealed several potential transcriptional regulatory elements such as Hunchback (Hb) and BR-C Z. Mutation of the core bases of the BR-C Z binding site demonstrated that BR-C Z induces 20E-mediated CYP6ab4 transcription. Further identification of cis- and trans-elements and their roles in the upregulation of CYP6ab4 may be useful for elucidating the contribution of P450 to the response mechanism to 20E.

Expression profile analysis of silkworm P450 family genes after phoxim induction.

Silkworm (Bombyx mori) is an important economic insect and a model species for Lepidopteran. Each year, O,O-diethyl O-(alpha-cyanobenzylideneamino) phosphorothioate (phoxim) pesticide poisoning in China results in huge economic losses in sericulture. Silkworm fat body is the main organ for nutrient storage, energy supply, intermediary metabolism, and detoxification. Microarray analysis of silkworm Cytochrome P450 detoxification enzyme genes revealed that all tested P450 4 (CYP4) family genes are expressed in the fat body. Quantitative Real-time PCR (QRT-PCR) was used to detect the expression of CYP4 family genes in silkworm fat body 0, 24, 48, and 72 h after phoxim exposure. The expression levels of silkworm molting hormone synthesis-related genes started to change 24 h after phoxim exposure, with those of CYP302A1, CYP306A1, and CYP314A1 being elevated by 1.38-, 1.33-, and 2.10-fold, respectively. The CYP18A1 gene that participates in steroid hormone inactivation and the CYP15C1 gene that participates in the epoxidation during the synthesis of juvenile hormone (JH) from methyl farnesoate (MF) were increased by 3.85- and 7.82-fold, respectively. Phylogenetic analysis indicated that these endogenous hormone metabolism-related genes belong to CYP mito clan and clan 2, and that phoxim exposure may affect silkworm development and metamorphosis. The CYP4, CYP6, and CYP9 families all showed some degrees of increases in gene expression; among them, CYP49A1, CYP4L6, CYP6AB4, CYP9G3, CYP9A19, and CYP9A22's transcription levels were significantly upregulated to 12.77-, 2.64-, 2.42-, 4.06-, 3.32-, and 2.98-fold, respectively, of the control levels. In the fat body, CYP49A1, CYP6AB4, CYP9A19, and CYP9A22 were constantly expressed at high levels after 24, 48, and 72 h of phoxim treatments; according to phylogenetic analysis, these genes belong to detoxification-related clan 3 and clan 4 CYP families. These genes may participate in the metabolism of phoxim in silkworm fat body. The results obtained in this study provide a basis for future in-depth investigations of insect P450 family genes in metabolic detoxification.

Molecular mechanisms of silk gland damage caused by phoxim exposure and protection of phoxim-induced damage by cerium chloride in Bombyx mori.

It is known that exposure to organophosphorus pesticides (OP) including phoxim can produce oxidative stress, neurotoxicity, and greatly attenuate cocooning rate in the silkworm, Bombyx mori. Cerium treatment has been demonstrated to relieve phoxim-induced toxicity in B. mori; however, very little is known about the molecular mechanisms of silk gland injury due to OP exposure and protection of gland damage due to cerium pretreatment. The aim of this study was to evaluate silk gland damage and its molecular mechanisms in phoxim-induced silkworm toxicity and the protective mechanisms of cerium following exposure to phoxim. The results showed that phoxim exposure resulted in severe gland damage, reductions in protein synthesis and the cocooning rate of silkworms. Cerium (Ce) attenuated gland damage caused by phoxim, promoted protein synthesis, increased the antioxidant capacity of the gland and increased the cocooning rate of B. mori. Furthermore, digital gene expression data suggested that phoxim exposure led to significant up-regulation of 714 genes and down-regulation of 120 genes. Of these genes, 122 were related to protein metabolism, specifically, the down-regulated Ser2, Ser3, Fib-L, P25, and CYP450. Ce pretreatment resulted in up-regulation of 162 genes, and down-regulation of 141 genes, importantly, Ser2, Ser3, Fib-L, P25, and CYP333B8 were up-regulated. Treatment with CeCl3 + phoxim resulted in higher levels of Fib-L, P25, Ser2, Ser3, CAT, TPx, and CYP333B8 expression in the silk gland of silkworms. These findings indicated that Ce increased cocooning rate via the promotion of silk protein synthesis-related gene expression in the gland under phoxim-induced toxicity. These findings may expand the application of rare earths in sericulture.

Mechanisms of larval midgut damage following exposure to phoxim and repair of phoxim-induced damage by cerium in Bombyx mori.

Bombyx mori is an important economic animal for silk production. However, it is liable to be infected by organophosphorus pesticide that can contaminate its food and growing environment. It has been known that organophosphorus pesticide including phoxim exposure may damage the digestive systems, produce oxidative stress and neurotoxicity in silkworm B. mori, whereas cerium treatment has been demonstrated to relieve phoxim-induced toxicity in B. mori. However, very little is known about the molecular mechanisms of midgut injury due to phoxim exposure and B. mori protection after cerium pretreatment. The aim of this study was to evaluate the midgut damage and its molecular mechanisms, and the protective role of cerium in B. mori following exposure to phoxim. The results showed that phoxim exposure led to severe midgut damages and oxidative stress; whereas cerium relieved midgut damage and oxidative stress caused by phoxim in B. mori. Furthermore, digital gene expression suggested that phoxim exposure led to significant up-regulation of 94 genes and down-regulation of 52 genes. Of these genes, 52 genes were related with digestion and absorption, specifically, the significant alterations of esterase, lysozyme, amylase 48, and lipase expressions. Cerium pretreatment resulted in up-regulation of 116 genes, and down-regulation of 29 genes, importantly, esterase 48, lipase, lysozyme, and α-amylase were up-regulated. Treatment with Phoxim + CeCl3 resulted in 66 genes up-regulation and 39 genes down-regulation; specifically, levels of esterase 48, lipase, lysozyme, and α-amylase expression in the midgut of silkworms were significantly increased. Therefore, esterase 48, lipase, lysozyme, and α-amylase may be potential biomarkers of midgut toxicity caused by phoxim exposure. These findings may expand the application of rare earths in sericulture.

Nanoparticulate TiO2 protection of midgut damage in the silkworm (Bombyx mori) following phoxim exposure.

Bombyx mori (B. mori) is often subjected to phoxim poisoning in China due to phoxim exposure, which leads to a decrease in silk production. Nanoparticulate (NP) titanium dioxide (nano-TiO2) has been shown to attenuate damages in B. mori caused by phoxim exposure. However, little is known about the molecular mechanisms of midgut injury due to organophosphorus insecticide exposure and its repair by nano-TiO2 pretreatment. In this study, phoxim exposure for 36 h led to significant decreases in body weight and survival and increased oxidative stress and midgut injury. Pretreatment with nano-TiO2 attenuated the phoxim-induced midgut injury, increased body weight and survival, and decreased oxidative stress in the midgut of B. mori. Digital gene-expression data showed that exposure to phoxim results in significant changes in the expression of 254 genes in the phoxim-exposed midgut and 303 genes in phoxim + nano-TiO2-exposed midgut. Specifically, phoxim exposure led to upregulation of Tpx, α-amylase, trypsin, and glycoside hydrolase genes involved in digestion and absorption. Phoxim exposure also led to the downregulation of Cyp450 and Cyp4C1 genes involved in an antioxidant capacity. In contrast, a combination of both phoxim and nano-TiO2 treatment significantly decreased the change in α-amylase, trypsin, and glycoside hydrolases (GHs), which are involved in digestion and absorption. These results indicated that Tpx, α-amylase, trypsin, GHs, Cyp450, and Cyp4C1 may be potential biomarkers of midgut toxicity caused by phoxim exposure and the attenuation of these toxic impacts by nano-TiO2.

BmCREC is an endoplasmic reticulum (ER) resident protein and required for ER/Golgi morphology.

Silkworm posterior silkgland is a model for studying intracellular trafficking. Here, using this model, we identify several potential cargo proteins of BmKinesin-1 and focus on one candidate, BmCREC. BmCREC (also known as Bombyx mori DNA supercoiling factor, BmSCF) was previously proposed to supercoil DNA in the nucleus. However, we show here that BmCREC is localized in the ER lumen. Its C-terminal tetrapeptide HDEF is recognized by the KDEL receptor, and subsequently it is retrogradely transported by coat protein I (COPI) vesicles to the ER. Lacking the HDEF tetrapeptide of BmCREC or knocking down COPI subunits results in decreased ER retention and simultaneously increased secretion of BmCREC. Furthermore, we find that BmCREC knockdown markedly disrupts the morphology of the ER and Golgi apparatus and leads to a defect of posterior silkgland tube expansion. Together, our results clarify the ER retention mechanism of BmCREC and reveal that BmCREC is indispensable for maintaining ER/Golgi morphology.

The expression profile and promoter analysis of ultraspiracle gene in the silkworm Bombyx mori.

The nuclear receptor, ultraspiracle protein (USP), is a transcription factor and an essential component of a heterodimeric receptor complex with ecdysone receptor. However, the mechanisms underlying the transcriptional regulation of USP in silkworm are unknown. In this study, using dual-spike-in qPCR method, we examined the expression of Bombyx ultraspiracle gene (BmUSP) in various tissues of silkworm as well as expression changes after stimulation with ecdysone. The results showed that the expression levels of BmUSP gene varied in different tissues and were increased 2 h after exposure to ecdysone. To identify the molecular mechanism underlying the regulation of USP gene expression in silkworm Bombyx mori, promoter truncation analyses were performed using the luciferase reporter assay and Bac-to-Bac expression system in several tissues of B. mori. BmUSP gene promoter with 5' end serial deletions showed different levels of activity in various tissues, higher in fat body and Malpighian tubule. Deletion of the region from -485 to -445 and -307 to -281 upstream of BmUSP gene abolished and increased its promoter activity, respectively. This region contains AP-1, Dfd transcription factor binding sites. These results indicate that BmUSP are expressed at different levels in different tissues of the silkworm, but all are subjected to the regulation by ecdysone. This study would provide an important foundation for investigating the mechanism underlying the transcriptional regulation of BmUSP in the silkworm.

Identification and characterization of six cytochrome P450 genes belonging to CYP4 and CYP6 gene families in the silkworm, Bombyx mori.

It was predicted that the genome of silkworm, Bombyx mori, has at least 79 P450 genes; however, P450 genes that are related to the catabolism of exogenous compounds were not reported. In this study we cloned two CYP4 (named CPY4M5 and CYP4M9) and four CYP6 (named CYP6AB5, CYP6AE9, CYP6AE22 and CYP6AU1) genes by using both bioinformatics and RT-PCR approaches. Sequence analysis showed that these genes contained conserved P450 gene sequence regions and one conserved intron. CYP4M5 and CYP4M9 genes were clustered together in a mode of "head-to-tail" possibly due to gene duplication. Blast analysis showed that these P450 genes shared significant similarity with CYP4 and CYP6 genes that are involved in the catabolism and detoxification of exogenous compounds in other insect species. RT-PCR results showed that these P450 genes were highly expressed in the midgut and fat body of B. mori. As the instar age increased, these P450 genes exhibit different expression patterns. When B. mori was exposed to 1.75 × 10(-5)% of cypermethrin, 3.5 × 10(-6)% of cypermethrin and 0.1% of rutin, expression of CYP6AB5 was increased by 2.3-fold, 2.2-fold and 1.9-fold, respectively. Exposure of B. mori to 0.1% quercetin does not change the expression of CYP6AB5. In contrast, expression of the other five P450 genes was inhibited after exposed to these compounds.

The expression profile and promoter analysis of ß-N-acetylglucosaminidases in the silkworm Bombyx mori.

ß-N-acetylglucosaminidase (GlcNAcase) is a key enzyme in the chitin decomposition process. In this study, we investigated the gene expression profile of GlcNAcases and the regulation mechanism for one of these genes, BmGlcNAcase1, in the silkworm. We performed sequence analysis of GlcNAcase. Using dual-spike-in qPCR method, we examined the expression of Bombyx ß-N-acetylglucosaminidases (BmGlcNAcases) in various tissues of silkworm as well as expression changes after stimulation with ecdysone. Using Bac-to-Bac system and luciferase reporter vectors, we further analyzed the promoter sequence of BmGlcNAcase1. The results showed that these proteins have a highly conserved catalytic domain. The expression levels of the BmGlcNAcase genes varied in different tissues, and were increased 48 h after exposure to ecdysone. BmGlcNAcase1 gene promoter with 5'-end serial deletions showed different levels of activity in various tissues, higher in the blood, skin and fat body. Deletion of the region from -347 to -223 upstream of BmGlcNAcase-1 gene abolished its promoter activity. This region contains the binding sites for key transcription factors including Hb, BR-C Z, the HSF and the typical TATA-box element. These results indicate that BmGlcNAcases are expressed at different levels in different tissues of the silkworm, but all are subjected to the regulation by ecdysone. BmGlcNAcase1 promoter analysis has paved a foundation for further study of the gene expression patterns.

Functional study on the mutations in the silkworm (Bombyx mori) acetylcholinesterase type 1 gene (ace1) and its recombinant proteins.

The acetylcholinesterase of Lepidoptera insects is encoded by two genes, ace1 and ace2. The expression of the ace1 gene is significantly higher than that of the ace2 gene, and mutations in ace1 are one of the major reasons for pesticide resistance in insects. In order to investigate the effects of the mutations in ace1's characteristic sites on pesticide resistance, we generated mutations for three amino acids using site-directed mutagenesis, which were Ala(GCG)303Ser(TCG), Gly(GGA)329Ala(GCA) and Leu (TCT)554Ser(TTC). The Baculovirus expression system was used for the eukaryotic expression of the wild type ace1 (wace1) and the mutant ace1 (mace1). SDS-PAGE and Western blotting were used to detect the targeting proteins with expected sizeof about 76 kDa. The expression products were purified for the determination of AChE activity and the inhibitory effects of physostigmine and phoxim. We observed no significant differences in the overall activity of the wild type and mutant AChEs. However, with 10 min of physostigmine (10 µM) inhibition, the remaining activity of the wild type AChE was significantly lower than that of the mutant AChE. Ten min inhibition with 33.4 µM phoxim also resulted in significantly lower remaining activity of the wild type AChE than that of the mutant AChE. These results indicated that mutations for the three amino acids reduced the sensitivity of AChE to physostigmine and phoxim, which laid the foundation for future in vivo studies on AChE's roles in pesticide resistance.

Expression analysis and RNA interference of BmCarE-10 gene from Bombyx mori.

Carboxylesterase (CarE) is a multifunctional superfamily, and it plays important roles in xenobiotic detoxification, pheromone degradation, neurogenesis and regulating development. In this research, firstly, we measured the rutin-induced transcriptional level of BmCarE-10 gene by using real-time quantitative RT-PCR method, and dual spike-in strategy. Several possible physiological functions were certified preliminarily by RNAi experiments in silkworm. Promoter truncation analysis using a dual-luciferase reporter assay in Bombyx mori ovary cells (BmN) showed that the region -705 to -625 for BmCarE-10 gene was essential for basal and rutin-induced transcriptional activity. Sequence analysis of this region revealed several potential transcriptional regulatory elements such as Croc and Dfd. The activities of the BmCarE-10 promoter in various tissues of silkworm were also measured by firefly luciferase activity and normalized by the Renilla luciferase activity. Results showed that the activity of the BmCarE-10 promoter were highest in the Malpighian tubule, followed by fat body, silk gland, midgut, epidermis, and hemocyte. The essential region for basal and rutin-induced transcriptional activity was also -894 to -502 in Malpighian tubule and fat body of silkworm. The potential core promoters of BmCarE-10 gene in B. mori are reported for the first time in this research. Further identification of cis- and trans-elements and their role in upregulation of BmCarE-10 gene may be useful for elucidating the contribution of CarE protein to the response mechanism to rutin.

Effects of the biosynthesis and signaling pathway of ecdysterone on silkworm (Bombyx mori) following exposure to titanium dioxide nanoparticles.

Silkworm (Bombyx mori), a model Lepidoptera insect, is economically important. Its growth and development are regulated by endogenous hormones. During the process of transition from larvae to pupae, 20-hydroxyecdysone (20E) plays an important role. The recent surge in consumer products and applications using metallic nanoparticles has increased the possibility of human or ecosystem exposure due to their unintentional release into the environment. We investigated the effects of exposure to titanium dioxide nanoparticles (TiO2 NPs) on the action of 20E in B. mori. Titanium dioxide nanoparticle treatment shortened the molting duration by 8 hr and prolonged the molting peak period by 10 %. Solexa sequencing profiled the changes in gene expression in the brain of fifth-instar B. mori in response to TiO2NPS exposure for 72 hr, to address the effects on hormone metabolism and regulation. Thirty one genes were differentially expressed. The transcriptional levels of pi3k and P70S6K, which are involved in the target of the rapamycin (TOR) signaling pathway, were up-regulated. Transcriptional levels of four cytochrome P450 genes, which are involved in 20E biosynthesis, at different developmental stages (48, 96, 144, and 192 hr) at 5th instars of all displayed trends of increasing expression. Simultaneously, the ecdysterone receptors, also displayed increasing trends. The 20E titers at four developmental stages during the 5th instar were 1.26, 1.23, 1.72, and 2.16 fold higher, respectively, than the control group. These results indicate that feeding B. mori with TiO2 NPs stimulates 20E biosynthesis, shortens the developmental progression, and reduces the duration of molting. Thus, application of TiO2 NPs is of high significance for saving the labor force in sericulture, and our research provides a reference for the ecological problems in the field of Lepidoptera exposured to titanium dioxide nanoparticles.

Phoxim-induced damages of Bombyx mori larval midgut and titanium dioxide nanoparticles protective role under phoxim-induced toxicity.

Phoxim (O,O-diethyl O-(alpha-cyanobenzylideneamino) phosphorothioate) is a powerful organophosphorus pesticide with high potential for Bombyx mori larvae of silkworm exposure. However, it is possible that during the phoxim metabolism, there is generation of reactive oxygen species (ROS) and phoxim may produce oxidative stress and neurotoxicity in an intoxicated silkworm. Titanium dioxide nanoparticles (TiO2 NPs) pretreatment has been demonstrated to increase antioxidant capacity and acetylcholinesterase (AChE) activity in organisms. This study was, therefore, undertaken to determine phoxim-induced oxidative stress and neurotoxicity to determine whether phoxim intoxication alters the antioxidant system and AChE activity in the B. mori larval midgut, and to determine whether TiO2 NPs pretreatment attenuates phoxim-induced toxicity. The findings suggested that phoxim exposure decreased survival of B. mori larvae, increased malondialdehyde (MDA), carbonyl and 8-OHdG levels, and ROS accumulation in the midgut. Furthermore, phoxim significantly decreased the activities of AChE, superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), glutathione-S-transferase (GST), and levels of ascorbic acid (AsA), reduced glutathione (GSH), and thiol in the midgut. TiO2 pretreatment, however, could increase AChE activity, and remove ROS via activating SOD, CAT, APX, GR, and GST, and accelerating AsA-GSH cycle, thus attenuated lipid, protein, and DNA peroxidation and improve B. mori larval survival under phoxim-induced toxicity. Moreover, this experimental system would help nanomaterials to be applied in the sericulture.

Analyzing the promoters of two CYP9A genes in the silkworm Bombyx mori by dual-luciferase reporter assay.

Cytochrome P450s (CYPs) are widespread proteins that interact with exogenous chemicals from the diet or the environment. CYP9A subfamily genes are important in the silkworm Bombyx mori. We previously reported transcriptional levels of two CYP9A genes in different tissues and their responses to sodium fluoride (NaF). In this study, promoter truncation analysis using a dual-luciferase reporter assay in B. mori ovary cells (BmN) showed that the regions -1,496 to -1,102 bp for CYP9A19, and -1,630 to -1,210 bp for CYP9A22 were essential for basal transcriptional activity. Sequence analysis of these regions revealed several transcriptional regulatory elements but no typical promoter elements. Promoter activities were regulated after NaF induction and with an obvious dose effect. Although the dual-luciferase assay has been widely used to determine the activity of a given promoter in cell lines, problems with it still exist. Our results indicate that both plasmid size and construct protocols affect the experimental results.

Structure and evolution of the mitochondrial genome of Exorista sorbillans: the Tachinidae (Diptera: Calyptratae) perspective.

The first complete mitochondrial genome (mitogenome) of Tachinidae Exorista sorbillans (Diptera) is sequenced by PCR-based approach. The circular mitogenome is 14,960 bp long and has the representative mitochondrial gene (mt gene) organization and order of Diptera. All protein-coding sequences are initiated with ATN codon; however, the only exception is Cox I gene, which has a 4-bp ATCG putative start codon. Ten of the thirteen protein-coding genes have a complete termination codon (TAA), but the rest are seated on the H strand with incomplete codons. The mitogenome of E. sorbillans is biased toward A+T content at 78.4 %, and the strand-specific bias is in reflection of the third codon positions of mt genes, and their T/C ratios as strand indictor are higher on the H strand more than those on the L strand pointing at any strain of seven Diptera flies. The length of the A+T-rich region of E. sorbillans is 106 bp, including a tandem triple copies of a13-bp fragment. Compared to Haematobia irritans, E. sorbillans holds distant relationship with Drosophila. Phylogenetic topologies based on the amino acid sequences, supporting that E. sorbillans (Tachinidae) is clustered with strains of Calliphoridae and Oestridae, and superfamily Oestroidea are polyphyletic groups with Muscidae in a clade.

Analysis of reference gene expression for real-time PCR based on relative quantitation and dual spike-in strategy in the silkworm Bombyx mori.

In general, for real-time quantitative polymerase chain reaction (qPCR), normalization strategies use a reference gene as a control and to avoid the introduction of experimental errors expression of this gene should not vary in response to changing conditions. However, the expression of many reference genes has been reported to vary considerably and, without appropriate normalization, the expression profile of a target gene can be misinterpreted. In this study, the expression levels of seven commonly used reference genes (ACT, GAPDH, 28srRNA, RPL3, α-tubulin, UBC, and TBP) were detected at different development time points and in response to treatment with 20-hydroxyecdysone (20E) and with rutin. The expression stability was analyzed using geNorm and NormFinder software. Significant variations were found among normal tissues and between experimentally treated tissues. The dual spike-in strategy also revealed significant variations of the expression levels of the reference genes among normal tissues and between experimentally treated tissues. Glutathione-S-transferase sigma 1 (GSTs1), which has a high expression level in fat body and is related to the mechanism of resistance, was used as a target gene to validate the feasibility and difference of these two approaches.

Expression of UreB and HspA of Helicobacter pylori in silkworm pupae and identification of its immunogenicity.

For mass production of urease B subunit (UreB) and heat shock protein A subunit (HspA) of Helicobacter pylori with Bombyx mori nuclear polyhedrosis virus (BmNPV) baculovirus expression system (BES) and to determine whether they could be used as an oral vaccine against H. pylori, besides, to determine the time course of expressed recombinant protein and the optimum acquisition time directly through green fluorescence, HspA and enhanced green fluorescence protein (EGFP) genes were cloned into vector pFastBacDual to form donor vector pFastBacDual-(EGFP) (HspA), UreB gene was cloned into vector pFastBacDual to form donor vector pFastBacDual-UreB,then they were transformed into E. coli BmDH10Bac to obtain the recombinant Bacmid-(EGFP) (HspA) and Bacmid-UreB respectively. They were used to transfect BmN cells and generated the recombinant baculovirus BmNPV-(EGFP) (HspA) and BmNPV-UreB. Using these recombinant baculovirus BmNPV-(EGFP) (HspA) and BmNPV-UreB inoculated the silkworm pupae, a recombinant HspA and UreB protein were expressed in silkworm pupae, which were around 13 and 62 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blot analysis. After oral immunization of mice, serum specific IgG antibodies against HspA and UreB in vaccine group were much higher than that in mock and native silkworm powder control groups. The results indicated that the expressed recombinant HspA and UreB in silkworm pupae would possess good immunogenicity. In addition, when EGFP and HspA proteins were expressed, a direct correlation between the increase in intensity of fluorescence and HspA concentration.