家蚕拟浆细胞具有吞噬功能

目的：通过观察家蚕Bombyx mori吞噬细胞的微细结构,来确定拟绛色细胞是否也具有吞噬功能。方法：用荧光小球微量注射家蚕pnd pS品系的幼虫,经荧光染色剂丫啶橙和碘化丙啶染色循环血细胞后,在荧光显微镜下观察并扫描拍摄。结果：观察发现除颗粒细胞和浆血细胞外,一些原血球细胞（血干细胞）和拟绛色细胞（多酚氧化酶）也能吞噬荧光小球。在拟绛色细胞里还发现许多和颗粒细胞一样的能被丫啶橙染色的颗粒。尽管在小球细胞中没有发现被吞噬的荧光小球,但该类血球有比较多的能被丫啶橙染色的大颗粒,这表明它们可能是已经被吞噬的凋亡小体。结论：除颗粒细胞和浆血细胞外,一些原血球细胞和拟绛色细胞也能吞噬荧光小球。说明拟绛色细胞也具有吞噬功能。     

Analysis of ESTs and gene expression patterns of the posterior silkgland in the fifth instar larvae of silkworm, Bombyx mori L.

The fibroin gene expression pattern and regulation of the posterior silkgland were studied by means of expressed sequence tags (ESTs) using the first and fifth day larvae of the fifth instar of silkworm, Bombyx mori L (strain: C 108). The results showed that there were 911 repetitive ESTs and 1950 single sequences (Singlets) among total 2861 consentient sequences, which were spliced. 1335 sequences were identified and the other 1526 were unknown. 5560 sequences (55.89%) in the posterior silkgland cell of the silkworm were new ESTs without homology with EST data published by Mita et al. The number of repetitive ESTs and single sequences from the first day larvae of the fifth instar was double more than that of the fifth day of the same instar in the silkworms. The unigenes which were more than 50 in repetitive EST size (contig size) came to only about 0.5% in total consentient sequences. There were significant differences between gene expression frequencies, and expressed genes were related to fibroin synthesis and its secretion and fibroin composition. Comparing the fifth day with the first day of the fifth instar, the genes-expressed quantity of fibroin heavy-chain gene was 18 fold higher, fibroin light-chain gene 9 fold and fibroin P52 gene 8 fold. 508 genes functioned for cellular component and 315 for enzyme after function tracing. These results implied that the gene expression of the first day was mainly for preparation for fibroin synthesis except for the growth of silkgland cells, and the gene expression of the fifth day of the fifth instar was mainly for synthesizing and excreting fibroin. Because the ratio of heavy chain, light chain and p25 of fibroin was not 6:6:1 as theoretically expected, or its special H-chain structure, the H-chain gene was not easy to detect through EST technique. Most of genes among total 2861 consentient sequences functioned for fibroin synthesis and secretion. This suggested the fibroin synthesis and secretion procedure of the posterior silkgland was more complex than the knowledge we have.     

家蚕化学诱变剂及诱导突变体的筛选

在家蚕Bombyx mori基因组计划完成之后,其功能基因组研究成为该领域的最重要课题。突变体是功能基因组学研究的重要材料,因此,通过人为诱导获取大量的突变系统是及其重要的手段。本研究用化学诱变剂ENU、MNU、DES、5-BU、EMS诱导处理家蚕标准品种C108,筛选获得了非滞育红卵,长圆筒茧、小茧、丝胶茧及绵茧突变体,致死突变体及无鳞毛蛾翅突变体。结果还表明： MNU、DES诱变家蚕的突变效率高,注射翅原基比腹部更方便且效果好,化学诱导雄体比雌体的效果好; 在时期上,注射蛹和蛾都有诱导效果。上述突变体大多为致死性突变,推测其可能与致死性基因突变有关。同时,本研究为应用TILLING技术鉴定家蚕更多目的基因突变体提供了有效的材料。     

一种家蚕类浓核病毒的组织病理学特征

本文从家蚕病蚕中分离到一种家蚕类浓核病毒（BmDNV-Like）,对它的组织病理学研究表明:该病毒首先寄生家蚕中肠柱状细胞,继而引起其细胞核的膨大和破裂;组织原位杂交结果表明该病毒既能在家蚕中肠柱状细胞中增殖,也能在中肠的杯形细胞中增殖,甚至在感染后期能在家蚕幼虫的大部分组织细胞中感染和增殖。     

The genome sequence of silkworm, Bombyx mori.

We performed threefold shotgun sequencing of the silkworm (Bombyx mori) genome to obtain a draft sequence and establish a basic resource for comprehensive genome analysis. By using the newly developed RAMEN assembler, the sequence data derived from whole-genome shotgun (WGS) sequencing were assembled into 49,345 scaffolds that span a total length of 514 Mb including gaps and 387 Mb without gaps. Because the genome size of the silkworm is estimated to be 530 Mb, almost 97% of the genome has been organized in scaffolds, of which 75% has been sequenced. By carrying out a BLAST search for 50 characteristic Bombyx genes and 11,202 non-redundant expressed sequence tags (ESTs) in a Bombyx EST database against the WGS sequence data, we evaluated the validity of the sequence for elucidating the majority of silkworm genes. Analysis of the WGS data revealed that the silkworm genome contains many repetitive sequences with an average length of <500 bp. These repetitive sequences appear to have been derived from truncated transposons, which are interspersed at 2.5- to 3-kb intervals throughout the genome. This pattern suggests that silkworm may have an active mechanism that promotes removal of transposons from the genome. We also found evidence for insertions of mitochondrial DNA fragments at 9 sites. A search for Bombyx orthologs to Drosophila genes controlling sex determination in the WGS data revealed 11 Bombyx genes and suggested that the sex-determining systems differ profoundly between the two species.     

Spindle-E is essential for gametogenesis in the silkworm,Bombyx mori

As a defense mechanism against transposable elements, the PIWI-interacting RNA (piRNA) pathway maintains genomic integrity and ensures proper gametogenesis in gonads. Numerous factors are orchestrated to ensure normal operation of the piRNA pathway. Spindle-E (Spn-E) gene was one of the first genes shown to participate in the piRNA pathway. In this study, we performed functional analysis of Spn-E in the model lepidopteran insect, Bombyx mori. Unlike the germline-specific expression pattern observed in Drosophila and mouse, BmSpn-E was ubiquitously expressed in all tissues tested, and it was highly expressed in gonads. Immunofluorescent staining showed that BmSpn-E was localized in both germ cells and somatic cells in ovary and was expressed in spermatocytes in testis. We used a binary transgenic CRISPR/Cas9 system to construct BmSpn-E mutants. Loss of BmSpn-E expression caused derepression of transposons in gonads. We also found that mutant gonads were much smaller than wild-type gonads and that the number of germ cells was considerably lower in mutant gonads. Quantitative real-time PCR analysis and TUNEL staining revealed that apoptosis was greatly enhanced in mutant gonads. Further, we found that the BmSpn-E mutation impacted gonadal development and gametogenesis at the early larval stage. In summary, our data provided the first evidence that BmSpn-E plays vital roles in gonadal development and gametogenesis in B. mori.     

Immune stimulation in the silkworm, Bombyx mori L., by CpG oligodeoxynucleotides

Synthetic ODNs containing unmethylated CpG dinucleotides are known to stimulate immune responses in vertebrates, but so far the effect has not been studied in insects. In this report, we describe an induction of immune response following injection of oligodeoxynucleotides (ODNs) into the insect hemocoel. The fifth instar silkworm (Bombyx mori L.) larvae were injected with several synthetic ODNs containing variable number of unmethylated CpG motifs, heat-denatured genomic DNA of B. mori itself, or intact genomic DNA to observe a new induction pattern in the insect immune mechanism. When the induction of immune response was examined based on the expression rates of genes for antibacterial peptides such as attacin and cecropin, we could confirm that it was triggered upon injection of ODNs. The expression was, however, neither dependent on numbers of CpG motifs nor methylation of CpGs in ODNs. Furthermore, it was confirmed that the presence of CpG in ODN was not involved in the induction pattern of insect immunity caused by ODNs, although it has been reported that vertebrates respond in a specific manner against invading ODNs containing CpG dinucleotides. In addition, insect immunity was not stimulated by injection of intact DNA from host. In contrast, the injection of denatured genomic DNA provoked the host immune reaction. Taken together, our data suggest that foreignness of ODNs or DNA might be a key factor in the induction of insect immunity.     

Functional analysis of four Gloverin-like genes in the silkworm, Bombyx mori

To identify genes involved in the innate immunity of the silkworm Bombyx mori, we constructed a cDNA library from the fat body of Escherichia coli-challenged B. mori larvae. Based on the expressed sequence tag (EST) data and whole genome shotgun sequence analysis, we found four Gloverin-like genes, BmGlov1-4, in the Bombyx genome. Northern blot and RT-PCR analysis showed that BmGlov1-4 were induced in the larval fat body after an immune challenge by the injection of E. coli; however, less induction was observed after the injection of a yeast Candida albicans. In silico sequence analysis revealed the presence of a motif homologous to NF-kappaB binding site in the upstream region of each BmGlov gene. Moreover, we expressed recombinant BmGlov1-4 proteins using the baculovirus expression system, and found that all the recombinant BmGlov1-4 significantly inhibited the growth of E. coli.     

Characterization of Argonaute family members in the silkworm,Bombyx mori

Abstract The Argonaute protein family is a highly conserved group of proteins, which have been implicated in RNA silencing in both plants and animals. Here, four members of the Argonaute family were systemically identified based on the genome sequence of Bombyx mori. Based on their sequence similarity, BmAgo1 and BmAgo2 belong to the Ago subfamily, while BmAgo3 and BmPiwi are in the Piwi subfamily. Phylogenetic analysis reveals that silkworm Argonaute family members are conserved in insects. Conserved amino acid residues involved in recognition of the 5′ end of the small RNA guide strand and of the conserved (aspartate, aspartate and histidine [DDH]) motif present in their PIWI domains suggest that these four Argonaute family members may have conserved slicer activities. The results of microarray expression analysis show that there is a low expression level for B. mori Argonaute family members in different tissues and different developmental stages, except for BmPiwi. All four B. mori Argonaute family members are upregulated upon infection with B. mori nucleopolyhedrovirus. The complete coding sequence of BmPiwi, the homolog of Drosophila piwi, was cloned and its expression occurred mainly in the area where spermatogonia and spermatocytes appear. Our results provide an overview of the B. mori Argonaute family members and suggest that they may have multiple roles. In addition, this is also the first report, to our knowledge, of the response of RNA silencing machinery to DNA virus infection in insects.     

丝蛋白合成和分泌期家蚕丝腺中有氧氧化特性分析

【目的】有氧氧化中葡萄糖(Glc)、丙酮酸(PA)、乙酰Co A(AC)、还原型吡啶核苷酸(NADH)和腺苷三磷酸(ATP)摩尔数的理论比值为1∶2∶2∶10∶30~32,而己糖激酶(HK)、磷酸果糖激酶1(PFK1)、丙酮酸激酶(PK)、丙酮酸脱氢酶(PDH)、柠檬酸合酶(CS)、异柠檬酸脱氢酶(ICDHm)、α-酮戊二酸脱氢酶(α-KGDH)、NADH泛醌还原酶(NCR)、琥珀酸泛醌还原酶(SCR)、泛醌细胞色素C还原酶(CCR)、细胞色素C氧化酶(CCO)和ATP合酶(AS)活性的理论比值为1∶1∶2∶2∶2∶2∶2∶10∶2∶12∶12∶26~28。本研究旨在分析丝蛋白合成和分泌期家蚕Bombyx mori丝腺有氧氧化的特性。【方法】利用分光光度法和高效液相色谱法测定了上述生化指标的变化。【结果】丝蛋白合成和分泌期家蚕丝腺中检测不到Glc,产物含量以1/30 ATP,1/10 NADH,1/2 AC和1/2 PA的顺序递增;糖酵解途径相关酶活性,以PFK1活性最低;三羧酸循环相关酶活性以1/2 ICDHm,1/2α-KGDH和1/2 CS的顺序递增;氧化磷酸化相关酶包括1/26 AS,1/10 NCR,1/2 SCR,1/12 CCR和1/12 CCO的活性以1/26 AS活性最低;1/26 AS,1/2 ICDHm,1/2 PDH和PFK1的活性依次递增。NADH含量、ATP含量、PFK1活性、PDH活性和NCR活性在丝蛋白合成期升高,但在丝蛋白分泌期下降。【结论】据此推测,家蚕丝腺中PFK1,ICDHm和AS分别是糖酵解途径、三羧酸循环和氧化磷酸化的限速酶;糖酵解途径、丙酮酸脱氢、三羧酸循环和氧化磷酸化速率依次递减;有氧氧化速率在丝蛋白合成期升高,相反在丝蛋白分泌期降低。     

家蚕感染蛹虫草后的生理生化变化

蛹虫草分生孢子侵染5龄家蚕Bombyx mori后,家蚕血淋巴中总糖、海藻糖、蛋白质和甘油酯含量均有不同程度的下降,其中甘油酯含量下降最为明显。海藻糖酶活性在侵染初期也明显降低。接种后家蚕体内的保护酶超氧化物歧化酶、过氧化物酶和过氧化氢酶活性也有较大变化,其中超氧化物歧化酶活性上升最为明显,在4日内由441.841 U/mL升至601.255 U/mL。     

Expression analysis of decapentaplegic gene in the silkworm,Bombyx mori

The decapentaplegic (dpp) gene in Drosophila is involved in multiple developmental processes, and is a highly conserved among various eukaryotic species, including Bombyx mori. Although the gene has well been characterized in Drosophila species the B. mori dpp has not yet been functionally analyzed. In this study, we analyzed the expression pattern of B. mori dpp in 12 different developmental days/stages (7 days for fifth instar larvae, 2 days for spinning stage, 2 days for pupal stages, and 1 day for adults) in both male and female silkworms using quantitative real‐time RT‐PCR (qRT‐PCR). mRNA expression of B. mori dpp was much higher in the female larvae up to the mid‐stage of the fifth instar compared with the corresponding male larvae. Similarly, dpp expression also was much higher in females during the eclosion period than that in the corresponding male pupae. During the embryonic stage, the expression level of the dpp gene was much higher compared to that of adult stage in both male and female silkworms. These results suggest that the B. mori dpp gene plays multiple roles in the developmental of B. mori.     

家蚕BmBrat基因的克隆与鉴定

NHL家族蛋白具有调控细胞增殖与分化的功能,在哺育动物中被广泛研究。本文克隆得到家蚕NHL蛋白家族成员BmBrat基因,通过RACE技术获得该基因cDNA全长序列为3 614 bp,其ORF为2 580 bp,编码859个氨基酸,预测其蛋白分子量为94.3 kDa,等电点为6.65。利用RT-PCR技术检测其在五龄3 d家蚕各组织表达情况,结果表明其在幼虫各组织均有表达,包括丝腺、中肠、脂肪体、马氏管等,且卵巢和头部表达量最高;胚胎时期表达谱分析显示其在胚胎发育第4天和第5天有高量表达。经原核表达、蛋白纯化及免疫小鼠后获得家蚕BmBrat多克隆抗体,且Western blotting及免疫荧光检测显示该抗体可以特异检测家蚕BmBrat蛋白;免疫荧光结果表明BmBrat蛋白定位于家蚕血细胞胞质中,为进一步研究BmBrat基因的生物学功能奠定了基础。     

Purification and characterization of cocoonase from the silkworm Bombyx mori

Cocoonase (CCN) which facilitates the degradation of a cocoon is recognized as a trypsin-like serine protease. In this study, CCN from the silkworm Bombyx mori was purified and comprehensively characterized. Its activity was maximal at about pH 9.8. It was stable above pH 3.4 at 4?°C and below 50?°C at pH 7.5. CuSO₄, FeSO₄, and ZnSO₄ showed inhibitory effects on CCN, but other salts improved activity. Typical trypsin inhibitors inhibited CCN, but the relative inhibitory activities were much lower than those against bovine trypsin. An extract of cocoon shells inhibited trypsin, but it was only slightly inhibitory against CCN. There were significant differences in catalytic efficiencies and substrate specificities as between CCN and bovine trypsin.     

家蚕Hox基因研究进展

Hox基因（homeobox genes）在昆虫躯体模式（body plan）的发育调控机制中扮演着重要角色,其表达具有严格的组织特异性和胚胎发育的程序性。家蚕Bombyx mori作为鳞翅目昆虫的代表,其Hox基因也陆续得到鉴定。在家蚕中存在一个拟复等位基因群--E群基因,其突变表型均与过剩斑纹和过剩附肢有关,这可能与Hox基因有着密切联系。家蚕全基因组测序完成后,发现其Hox基因簇中存在12个特有的homeobox基因（Bmshx1~Bmshx12）, 说明家蚕Hox基因可能具有独特的生物学意义。我们还利用家蚕基因芯片数据分析了Bmlab与Bmpb基因的组织表达特征。通过对家蚕Hox基因的研究,探索家蚕躯体模式建立机制,可望为解析其他鳞翅目昆虫的躯体模式的建立机制提供理论依据。本文就家蚕Hox基因的表达、功能及其与E群突变的关系等方面进行了综述。     

Identification of two arginases generated by alternative splicing in the silkworm, Bombyx mori

Arginase (EC 3.5.3.1) catalyzes the hydrolysis of arginine to ornithine and urea. Here, we have cloned two arginase cDNAs from the silkworm, Bombyx mori. The analysis of exon/intron structures showed that the two mRNAs named bmarg-r and bmarg-f were generated from a single gene by alternative usage of exons. The bmarg-r and bmarg-f were predicted to encode almost the same amino acid sequences, except that the latter had additional ten N-terminal residues. Recombinant bmARG-r and bmARG-f in Escherichia coli cell lysates were roughly similar to each other in enzymatic characteristics, which did not show large difference from those of arginases assayed by using tissue extracts. Differential RT-PCR experiments and tissue distribution analyses of arginase activity indicated that the bmarg-r gene is expressed in the male reproductive organs, especially in the glandula lacteola and vesicular seminalis, from which it is secreted to the seminal fluid and transferred to the female during copulation, whereas the bmarg-f gene is expressed in the larval and adult nonreproductive organs including the fat body and muscle, where the produced arginase proteins are considered to stay in the cells. Thus, the two silkworm arginase isoforms may have a difference in whether or not the product is excreted out of the cells in which it is synthesized.     

Functional analysis of novel sulfotransferases in the silkworm Bombyx mori

Sulfoconjugation plays a vital role in the detoxification of xenobiotics and in the metabolism of endogenous compounds. In this study, we aimed to identify new members of the sulfotransferase (SULT) superfamily in the silkworm Bombyx mori. Based on amino acid sequence and phylogenetic analyses, two new enzymes, swSULT ST1 and swSULT ST2, were identified that appear to belong to a distinct group of SULTs including several other insect SULTs. We expressed, purified, and characterized recombinant SULTs. While swSULT ST1 sulfated xanthurenic acid and pentachlorophenol, swSULT ST2 exclusively utilized xanthurenic acid as a substrate. Based on these results, and those concerning the tissue distribution and substrate specificity toward pentachlorophenol analyses, we hypothesize that swSULT ST1 plays a role in the detoxification of xenobiotics, including insecticides, in the silkworm midgut and in the induction of gametogenesis in silkworm ovary and testis. Collectively, the data obtained herein contribute to a better understanding of SULT enzymatic functions in insects.