Very Early Corona Treatment-Mediated Artificial Incubation of Silkworm Eggs and Germline Transformation of Diapause Silkworm Strains

Diapause is an important biological characteristic for many insect species to adapt to adverse environmental conditions and maintain the continuity of the race. Compared with the traditional hydrochloric acid or/and cold storage treatment methods, the artificial corona incubation technology of silkworm (Bombyx mori) eggs has many advantages including, the absence of pollution, easy operation and safety. However, this technology has not yet been applied in sericulture. In this study, we developed a novel artificial corona instrument to successfully disrupt the diapause of newly laid and refrigerated eggs from various Chinese and Japanese lineage silkworm strains. Subsequently, we invented a very early corona treatment (VECT) strategy to prevent the diapause of newly laid silkworm eggs within 4 h of oviposition. The hatching rates of the larvae were more than 95% in all diapause silkworm strains, which was comparable to the effect of the traditional HCl treatment strategy. In addition, we developed a combination strategy of VECT and pre-blastoderm microinjection and successfully created transgenic silkworms in various diapause strains. The results of the current study can aid in improving the corona artificial incubation technology and promote its application in sericulture.

A Microbiome Study Reveals Seasonal Variation in Endophytic Bacteria Among different Mulberry Cultivars

Knowledge of seasonal shifts in the bacterial community composition among different mulberry (Morus L.) cultivars will facilitate to develop the biocontrol phytopathogens strategy using endophytic bacteria. The present study investigated the endophytic bacterial communities of four mulberry cultivars that have different resistance to mulberry fruit sclerotiniosis using Illumina-based sequencing of the 16S rRNA gene fragment in spring and autumn. The results indicated that spring samples harbor higher bacterial operational taxonomic units (OTUs), α-diversity, and bacterial community complexity in comparison with autumn samples. The taxonomic composition analysis showed that the majority of endophytes were composed of Proteobacteria (genus level: Methylobaterium) and Actinobacteria in spring, while sequences classified as Proteobacteria (genus level: Pantoea and Pseudomonas) were abundant in autumn. Analysis of β-diversity also revealed endophytic bacteria were divided into two main groups by season. By comparison among different mulberry cultivars, we found that Pantoea, Methylobaterium, and Pseudomonas were the three major bacterial genera in all cultivars, while their relative abundances varied with cultivars and appeared no obvious relationship with resistance level of mulberry fruit sclerotiniosis. The complex correlation of the endophytic communities in susceptible mulberry cultivars was higher than that of the resistant cultivars. Overall, the findings suggested that season plays a key role in determining the mulberry endophytic bacterial communities, followed by host cultivar, and Proteobacteria was the predominant phylum in both seasons and different mulberry cultivars.

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Season played a key role in determining mulberry endophytic bacterial communities.

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Mulberry endophytic bacterial variation was not obviously related with cultivars.

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Mulberry recruited beneficial endophytes as potential biocontrol agents.

Ultrabithorax and abdominal-A specify the abdominal appendage in a dosage-dependent manner in silkworm, Bombyx mori

In insects, there is a considerable diversity in leg distribution on the body, including number, segmental arrangement, morphological identity and consequent function, but the genetic basis for these differences is not well understood. Here by positional cloning, we showed that a ~355 kb region, including Bombyx mori Ultrabithorax (BmUbx) and abdominal-A (Bmabd-A), was responsible for the silkworm mutant Kh-extra-crescents-like (E^Kh-l) that displayed additional thoracic limb-like legs on the first abdominal segment (A1) and occasionally on the second abdominal segment (A2). We found that BmUbx gene was downregulated at both messenger RNA level and protein level in E^Kh-l embryo, while its expression domain in the E^Kh-l embryo was almost the same as that in the wild type. Whereas Bmabd-A was upregulated at both levels and was ectopically overexpressed on the supernumerary leg-bearing segments in E^Kh-l. Compared with the previously reported E^cs-l mutant in which increased expression of both BmUbx and Bmabd-A gave rise to ectopic proleg-like appendages on the same segments, we propose that overexpressed Bmabd-A gene is capable to promote the outgrowth of extra leg appendages on A1 and A2 segments, whereas BmUbx gene is required to specify accurate morphologies of the ectopic legs in a dosage-dependent manner in silkworm. These results provide insights into how these hox genes regulate the leg morphologic diversity on the same segments.

Mulberry Transcription Factor MnDREB4A Confers Tolerance to Multiple Abiotic Stresses in Transgenic Tobacco

The dehydration responsive element binding (DREB) transcription factors have been reported to be involved in stress responses. Most studies have focused on DREB genes in subgroups A-1 and A-2 in herbaceous plants, but there have been few reports on the functions of DREBs from the A-3-A-6 subgroups and in woody plants. Moreover, mulberry trees are ecologically and economically important perennial woody plants, but there has been little research on its stress physiology, biochemistry and molecular biology. In this study, a DREB gene from the mulberry tree, designated as MnDREB4A, classified into the A-4 subgroup by our previous study, was selected for further characterization. Our results showed that the MnDREB4A protein was localized to the nucleus where it activated transcription. The promoter of MnDREB4A can direct prominent expression downstream of the β-glucuronidase (GUS) gene under heat, cold, drought and salt stress, and GUS staining was deepest after 12 h of stress treatment. The MnDREB4A-overexpression transgenic tobacco showed the improved growth phenotype under untreated conditions, such as greener leaves, longer roots, and lower water loss and senescence rates. Overexpression of MnDREB4A in tobacco can significantly enhance tolerance to heat, cold, drought, and salt stresses in transgenic plants. The leaf discs and seedlings of transgenic plants reduced leaf wilting and senescence rates compared to the wild type plants under the different stress conditions. Further investigation showed that transgenic plants also had higher water contents and proline contents, and lower malondialdehyde contents under untreated condition and stress conditions. Our results indicate that the MnDREB4A protein plays an important role in plant stress tolerance.

[Progress of studies on medicinal fungus Phellinus]

The real sanghuang is a new species belonging to the Inonotus, which is commonly used for cancer treatment and human immune system improvement. This review summarized the progress on the studies of Phellinus Quel in recent years, including its taxonomy status, bioactive components, pharmacodynamics, separation and purification technologies. In addition, some related problems and perspectives were also discussed.

Analysis of interaction between Bmhrp28 and BmPSI in sex-specific splicing of Bombyx mori Bmdsx gene

Bombyx mori BmHRP28 and BmPSI, which belong to the family of RNA-binding proteins, have been identified binding to the female-specific exon 4 of the sex-determining gene Bmdsx pre-mRNA. However, the relationships between BmHRP28 and BmPSI still remain unclear. In this study, we carried out yeast two-hybrid (Y2H) and co-immunoprecipitation (Co-IP) analyses to address them. Y2H analysis showed that there was little or no direct binding between the BmHRP28 and BmPSI proteins. Also, the Co-IP experiments revealed that BmHRP28 and BmPSI coexisted in a multiprotein complex. Our results suggested that BmHRP28 and BmPSI form a muliprotein complex to regulate the splicing of Bmdsx pre-mRNA, but are not directly bound to each other. In an effort to find other regulatory factors in the multiprotein complex, we constructed a silkworm Y2H cDNA library of male early embryo. By Y2H screening, we identified an RNA-binding protein BmSPX, a putative component of the spliceosome, binding to BmPSI. These results indicated that BmHRP28 and BmPSI make up a spliceosome complex to regulate Bmdsx splicing and that BmSPX is another potential protein involved in this process. Our study provides some clues to better understand the mechanism of sex determination in the silkworm.

Identification and molecular characterization of a chitin deacetylase from Bombyx mori peritrophic membrane

The insect midgut epithelium is generally lined with a unique chitin and protein structure, the peritrophic membrane (PM), which facilitates food digestion and protects the gut epithelium. PM proteins are important determinants for PM structure and formation. In this study, the silkworm Bombyx mori midgut PM protein BmCDA7 was identified by proteomic tools. The full-length BmCDA7 cDNA is 1357 bp; the deduced protein is composed of 379 amino acid residues and includes a 16 amino acid residue signal peptide, a putative polysaccharide deacetylase-like domain and 15 cysteine residues present in three clusters. The heterologously expressed proteins of the BmCDA7 gene in yeast displayed chitin deacetylase activity. Expression of B. mori BmCDA7 was detected in the midgut at both the transcriptional and translational levels. The BmCDA7 gene was expressed by the newly hatched silkworm larvae until day seven of the fifth instar and was expressed at a high level in the newly exuviated larvae of different instars. The functions and regulatory mechanism of BmCDA7, however, need further investigation.

Antennapedia is involved in the development of thoracic legs and segmentation in the silkworm, Bombyx mori

Homeotic genes, which are associated closely with body patterning of various species, specify segment identity. The Wedge eye-spot (Wes) is a new homeotic mutant located on the sixth linkage group. Homozygous Wes/Wes embryos are lethal and display a pair of antenna-like appendages under the mouthparts as well as fused thoracic segments. These mutants also exhibit a narrower eye-spot at the larval stage compared with the wild type. By positional cloning, we identified the candidate gene of the Wes locus, Bombyx mori Antennapedia (BmAntp). Two BmAntp transcripts were identified in the homozygote of the Wes mutant, including a normal form and an abnormal form with a 1570-bp insertion. Our data showed that the insertion element was a long interspersed nuclear element (LINE)-like transposon that destroyed the original open reading frame of BmAntp. Quantitative RT-PCR analysis showed that the expression levels of normal BmAntp transcripts were increased markedly in the Wes heterozygous larvae compared with the wild type. Furthermore, we performed RNAi of BmAntp and observed fused thoracic segments and defective thoracic legs in the developing embryos. Our results indicated that BmAntp is responsible for the Wes mutant and has an important role in determining the proper development of the thoracic segments. Our identification of a homeotic mutation in the silkworm is an important contribution to our understanding of the regulation of Hox genes at different levels of expression.

Expansion of the silkworm GMC oxidoreductase genes is associated with immunity

The glucose-methanol-choline (GMC) oxidoreductases constitute a large gene family in insects. Some of these enzymes play roles in developmental or physiological process, such as ecdysteroid metabolism. However, little is known about the functional diversity of the insect GMC family. Here, we identified 43 GMC genes in the silkworm genome, the largest number of GMC genes among all the insect genomes sequenced to date. Similar to the other insects, there is a highly conserved GMC cluster within the second intron of the silkworm flotillin-2 (flo-2) gene. However, the silkworm GMC genes outside of the conserved GMC cluster have experienced a large expansion. Phylogenetic analysis suggested that the silkworm GMCβ subfamily contained 22 copies and made a major contribution to expansion of the silkworm GMC genes. Eighteen of the 22 members of the silkworm GMCβ subfamily are located outside of the conserved GMC cluster, and are known as silkworm expansion genes (SEs). Relative-rate tests showed that SEs evolved significantly faster than the GMCβ genes inside the conserved GMC cluster. Accordingly, the third position GC content (GC3s) and codon bias of SEs are significantly different from those of the GMCβ genes in the conserved GMC cluster. The elevated evolutionary rate of the silkworm GMCβ genes outside of the conserved GMC cluster may reflect the evolution of function diversity. At least 24 of the 43 silkworm GMC genes were differently transcribed and expressed in a tissue- or stage-specific manner during the larval stage. Strikingly, microarray data revealed that four different pathogens upregulated most of the silkworm GMCβ genes. Furthermore, RNA interference of representative upregulated GMCβ genes reduced the survival rate of the silkworm when infected by pathogens. Taken together, the results suggested that expansion of the silkworm GMC oxidoreductase genes is associated with immunity.

[Computational approaches for identification and classification of transposable elements in eukaryotic genomes]

Repetitive sequences (repeats) represent a significant fraction of the eukaryotic genomes and can be divided into tandem repeats, segmental duplications, and interspersed repeats on the basis of their sequence characteristics and how they are formed. Most interspersed repeats are derived from transposable elements (TEs). Eukaryotic TEs have been subdivided into two major classes according to the intermediate they use to move. The transposition and amplification of TEs have a great impact on the evolution of genes and the stability of genomes. However, identification and classification of TEs are complex and difficult due to the fact that their structure and classification are complex and diverse compared with those of other types of repeats. Here, we briefly introduced the function and classification of TEs, and summarized three different steps for identification, classification and annotation of TEs in eukaryotic genomes: (1) assembly of a repeat library, (2) repeat correction and classification, and (3) genome annotation. The existing computational approaches for each step were summarized and the advantages and disadvantages of the approaches were also highlighted in this review. To accurately identify, classify, and annotate the TEs in eukaryotic genomes requires combined methods. This review provides useful information for biologists who are not familiar with these approaches to find their way through the forest of programs.

FLP recombinase-mediated site-specific recombination in silkworm, Bombyx mori

A comprehensive understanding of gene function and the production of site-specific genetically modified mutants are two major goals of genetic engineering in the post-genomic era. Although site-specific recombination systems have been powerful tools for genome manipulation of many organisms, they have not yet been established for use in the manipulation of the silkworm Bombyx mori genome. In this study, we achieved site-specific excision of a target gene at predefined chromosomal sites in the silkworm using a FLP/FRT site-specific recombination system. We first constructed two stable transgenic target silkworm strains that both contain a single copy of the transgene construct comprising a target gene expression cassette flanked by FRT sites. Using pre-blastoderm microinjection of a FLP recombinase helper expression vector, 32 G3 site-specific recombinant transgenic individuals were isolated from five of 143 broods. The average frequency of FLP recombinase-mediated site-specific excision in the two target strains genome was approximately 3.5%. This study shows that it is feasible to achieve site-specific recombination in silkworms using the FLP/FRT system. We conclude that the FLP/FRT system is a useful tool for genome manipulation in the silkworm. Furthermore, this is the first reported use of the FLP/FRT system for the genetic manipulation of a lepidopteran genome and thus provides a useful reference for the establishment of genome manipulation technologies in other lepidopteran species.

Pathogen-origin horizontally transferred genes contribute to the evolution of Lepidopteran insects

Background

Horizontal gene transfer (HGT), a source of genetic variation, is generally considered to facilitate hosts' adaptability to environments. However, convincing evidence supporting the significant contribution of the transferred genes to the evolution of metazoan recipients is rare.

Results

In this study, based on sequence data accumulated to date, we used a unified method consisting of similarity search and phylogenetic analysis to detect horizontally transferred genes (HTGs) between prokaryotes and five insect species including Drosophila melanogaster, Anopheles gambiae, Bombyx mori, Tribolium castaneum and Apis mellifera. Unexpectedly, the candidate HTGs were not detected in D. melanogaster, An. gambiae and T. castaneum, and 79 genes in Ap. mellifera sieved by the same method were considered as contamination based on other information. Consequently, 14 types of 22 HTGs were detected only in the silkworm. Additionally, 13 types of the detected silkworm HTGs share homologous sequences in species of other Lepidopteran superfamilies, suggesting that the majority of these HTGs were derived from ancient transfer events before the radiation of Ditrysia clade. On the basis of phylogenetic topologies and BLAST search results, donor bacteria of these genes were inferred, respectively. At least half of the predicted donor organisms may be entomopathogenic bacteria. The predicted biochemical functions of these genes include four categories: glycosyl hydrolase family, oxidoreductase family, amino acid metabolism, and others.

Conclusions

The products of HTGs detected in this study may take part in comprehensive physiological metabolism. These genes potentially contributed to functional innovation and adaptability of Lepidopteran hosts in their ancient lineages associated with the diversification of angiosperms. Importantly, our results imply that pathogens may be advantageous to the subsistence and prosperity of hosts through effective HGT events at a large evolutionary scale.

Molecular cloning and characterization of Ecdysone oxidase and 3-dehydroecdysone-3α-reductase involved in the ecdysone inactivation pathway of silkworm, Bombyx mori

Molting hormone (ecdysteroid) is one of the most important hormones in insects. The synthesis and inactivation of the ecdysteroid regulate the developmental process of insects. A major pathway of ecdysone inactivation is that ecdysone is converted to 3-dehydroecdysone, and then further to 3-epiecdysone in insects. Two enzymes (ecdysone oxidase: EO and 3DE-3α-reductase) participate in this pathway. In this study, based on the previously characterized cDNAs in Spodoptera littoralis, we cloned and characterized EO and 3DE-3α-reductase genes in the silkworm, Bombyx mori. The heterologously expressed proteins of the two genes in yeast showed the ecdysone oxidase and 3DE-3α-reductase activities, respectively. Expression of BmEO was only detected in the midgut at transcriptional and translational levels. We also localized EO within the midgut goblet cell cavities. For Bm3DE-3α-reductase gene, RT-PCR and western blot showed that it was expressed in the midgut and the Malpighian tubules. Moreover, we localized 3DE-3α-reductase within the midgut goblet cell cavities and the cytosol of principal cells of the Malpighian tubules. These two genes have similar expression profiles during different developmental stages. Both genes were highly expressed at the beginning of the 5^th instar, and remained a relative low level during the feeding stage, and then were highly expressed at the wandering stage. All these results showed that the profiles of the two genes were well correlated with the ecdysteroid titer. The functional characterization of the enzymes participating in ecdysone inactivation in the silkworm provides hints for the artificial regulation of the silkworm development and biological control of pests.

Topological and functional characterization of an insect gustatory receptor

Insect gustatory receptors are predicted to have a seven-transmembrane structure and are distantly related to insect olfactory receptors, which have an inverted topology compared with G-protein coupled receptors, including mammalian olfactory receptors. In contrast, the topology of insect gustatory receptors remains unknown. Except for a few examples from Drosophila, the specificity of individual insect gustatory receptors is also unknown. In this study, the total number of identified gustatory receptors in Bombyx mori was expanded from 65 to 69. BmGr8, a silkmoth gustatory receptor from the sugar receptor subfamily, was expressed in insect cells. Membrane topology studies on BmGr8 indicate that, like insect olfactory receptors, it has an inverted topology relative to G protein-coupled receptors. An orphan GR from the bitter receptor family, BmGr53, yielded similar results. We infer, from the finding that two distantly related BmGrs have an intracellular N-terminus and an odd number of transmembrane spans, that this is likely to be a general topology for all insect gustatory receptors. We also show that BmGr8 functions independently in Sf9 cells and responds in a concentration-dependent manner to the polyalcohols myo-inositol and epi-inositol but not to a range of mono- and di-saccharides. BmGr8 is the first chemoreceptor shown to respond specifically to inositol, an important or essential nutrient for some Lepidoptera. The selectivity of BmGr8 responses is consistent with the known responses of one of the gustatory receptor neurons in the lateral styloconic sensilla of B. mori, which responds to myo-inositol and epi-inositol but not to allo-inositol.

Evidence of selection at melanin synthesis pathway loci during silkworm domestication

The domesticated silkworm (Bombyx mori) was domesticated from wild silkworm (Bombyx mandarina) more than 5,000 years ago. During domestication, body color between B. mandarina and B. mori changed dramatically. However, the molecular mechanism of the silkworm body color transition is not known. In the present study, we examined within- and between-species nucleotide diversity for eight silkworm melanin synthesis pathway genes, which play a key role in cuticular pigmentation of insects. Our results showed that the genetic diversity of B. mori was significantly lower than that of B. mandarina and 40.7% of the genetic diversity of wild silkworm was lost in domesticated silkworm. We also examined whether position effect exists among melanin synthesis pathway genes in B. mandarina and B. mori. We found that the upstream genes have significantly lower levels of genetic diversity than the downstream genes, supporting a functional constraint hypothesis (FCH) of metabolic pathway, that is, upstream enzymes are under greater selective constraint than downstream enzymes because upstream enzymes participate in biosynthesis of a number of metabolites. We also investigated whether some of the melanin synthesis pathway genes experienced selection during domestication. Neutrality test, coalescent simulation, as well as network and phylogenetic analyses showed that tyrosine hydroxylase (TH) gene was a domestication locus. Sequence analysis further suggested that a putative expression enhancer (Abd-B-binding site) in the intron of TH gene might be disrupted during domestication. TH is the rate-limiting enzyme of melanin synthesis pathway in insects. Real-time polymerase chain reaction assay did show that the relative expression levels of TH gene in B. mori were significantly lower than that in B. mandarina at three different developmental stages, which is consistent with light body color of domesticated silkworm relative to wild silkworm. Therefore, we speculated that expression change of TH gene may contribute to the body color transition from B. mandarina to B. mori. Our results emphasize the exceptional role of gene expression regulation in morphological transition of domesticated animals.

Nucleotide diversity and selection signature in the domesticated silkworm, Bombyx mori, and wild silkworm, Bombyx mandarina

To investigate the patterns of nucleotide diversity in domesticated silkworm, Bombyx mori L. (Lepidoptera: Bombycidae) and its wild relative, Chinese wild silkworm, Bombyx mandarina Moore, we sequenced nine nuclear genes. Neutrality test and coalescent simulation for these genes were performed to look at bottleneck intensity and selection signature; linkage disequilibrium (LD) within and between loci was employed to investigate allele association. As a result, B. mori lost 33-49% of nucleotide diversity relative to wild silkworm, which is similar to the loss levels found in major cultivated crops. Diversity of B. mori is significantly lower than that of B. mandarina measured as π(total) (0.01166 vs. 0.1741) or θ(W)(0.01124 vs. 0.02206). Bottleneck intensity of domesticated silkworm is 1.5 (in terms of k = N(b) /d, N(b) -bottleneck population size; d-bottleneck duration) with different durations. Gene DefA showed signature of artificial selection by all analysis methods and might experience strong artificial selection in B. mori during domestication. For nine loci, both curves of LD decay rapidly within 200 bp and drop slowly when distance is > 200 bp, although that of B. mori decays slower than B. mandarina at loci investigated. However, LD could not be estimated at DefA in B. mori and at ER in both silkworms. Elevated LD observed in B. mori may be indicator of selection and demographic events.

Comparative genetic diversity and genetic structure of three Chinese silkworm species Bombyx mori L. (Lepidoptera: Bombycidae), Antheraea pernyi Guérin-Meneville and Samia cynthia ricini Donovan (Lepidoptera: Saturniidae)

The genetic diversity and genetic structure of three Chinese silkworm species Bombyx mori L., Antheraea pernyi Guérin-Meneville and Samia cynthia ricini Donovan were comparatively assessed based on RAPD markers. At the species level, A. pernyi and B. mori showed high levels of genetic diversity, whereas S. cynthia ricini showed low level of genetic diversity. However, at the strain level, A. pernyi had relatively highest genetic diversity and B. mori had lowest genetic diversity. Analysis of molecular variance (AMOVA) suggested that 60% and 72% of genetic variation resided within strains in A. pernyi and S. cynthia ricini, respectively, whereas only 16% of genetic variation occurred within strains in B. mori. In UPGMA dendrogram, individuals of A. pernyi and B. mori formed the strain-specific genetic clades, whereas those of S. cynthia ricini were distributed in a mixed way. The implications of these results for the conservation and utilization in breeding programs of three silkworm species are discussed.

Burst expansion, distribution and diversification of MITEs in the silkworm genome

Background

Miniature inverted-repeat transposable elements (MITEs) are widespread in plants and animals. Although silkworm (Bombyx mori) has a large amount of and a variety of transposable elements, the genome-wide information of the silkworm MITEs is unknown.

Results

We used structure-based and homology approaches to search for MITEs in the silkworm genome. We identified 17 MITE families with a total of 5785 members, accounting for ~0.4% of the genome. 7 of 17 MITE families are completely novel based on the nucleotide composition of target site duplication (TSD) and/or terminal inverted repeats (TIR). Silkworm MITEs were widely and nonrandom distributed in the genome. One family named BmMITE-2 might experience a recent burst expansion. Network and diversity analyses for each family revealed different diversification patterns of the silkworm MITEs, reflecting the signatures of genome-shocks that silkworm experienced. Most silkworm MITEs preferentially inserted into or near genes and BmMITE-11 that encodes a germline-restricted small RNA might silence its the closest genes in silkworm ovary through a small RNA pathway.

Conclusions

Silkworm harbors 17 MITE families. The silkworm MITEs preferred to reside in or near genes and one MITE might be involved in gene silence. Our results emphasize the exceptional role of MITEs in transcriptional regulation of genes and have general implications to understand interaction between MITEs and their host genome.

Genome-wide identification and expression analysis of serine proteases and homologs in the silkworm Bombyx mori

Background

Serine proteases (SPs) and serine proteases homologs (SPHs) are a large group of proteolytic enzymes, with important roles in a variety of physiological processes, such as cell signalling, defense and development. Genome-wide identification and expression analysis of serine proteases and their homologs in the silkworm might provide valuable information about their biological functions.

Results

In this study, 51 SP genes and 92 SPH genes were systematically identified in the genome of the silkworm Bombyx mori. Phylogenetic analysis indicated that six gene families have been amplified species-specifically in the silkworm, and the members of them showed chromosomal distribution of tandem repeats. Microarray analysis suggests that many silkworm-specific genes, such as members of SP_fam12, 13, 14 and 15, show expression patterns that are specific to tissues or developmental stages. The roles of SPs and SPHs in resisting pathogens were investigated in silkworms when they were infected by Escherichia coli, Bacillus bombysepticus, Batrytis bassiana and B. mori nucleopolyhedrovirus, respectively. Microarray experiment and real-time quantitative RT-PCR showed that 18 SP or SPH genes were significantly up-regulated after pathogen induction, suggesting that SP and SPH genes might participate in pathogenic microorganism resistance in B. mori.

Conclusion

Silkworm SP and SPH genes were identified. Comparative genomics showed that SP and SPH genes belong to a large family, whose members are generated mainly by tandem repeat evolution. We found that silkworm has species-specific SP and SPH genes. Phylogenetic and microarray analyses provide an overview of the silkworm SP and SPHs, and facilitate future functional studies on these enzymes.

Mitochondrial genome nucleotide substitution pattern between domesticated silkmoth, Bombyx mori, and its wild ancestors, Chinese Bombyx mandarina and Japanese Bombyx mandarina

Bombyx mori and Bombyx mandarina are morphologically and physiologically similar. In this study, we compared the nucleotide variations in the complete mitochondrial (mt) genomes between the domesticated silkmoth, B. mori, and its wild ancestors, Chinese B. mandarina (ChBm) and Japanese B. mandarina (JaBm). The sequence divergence and transition mutation ratio between B. mori and ChBm are significantly smaller than those observed between B. mori and JaBm. The preference of transition by DNA strands between B. mori and ChBm is consistent with that between B. mori and JaBm, however, the regional variation in nucleotide substitution rate shows a different feature. These results suggest that the ChBm mt genome is not undergoing the same evolutionary process as JaBm, providing evidence for selection on mtDNA. Moreover, investigation of the nucleotide sequence divergence in the A+T-rich region of Bombyx mt genomes also provides evidence for the assumption that the A+T-rich region might not be the fastest evolving region of the mtDNA of insects.

Annotation and expression of carboxylesterases in the silkworm, Bombyx mori

BACKGROUND

Carboxylesterase is a multifunctional superfamily and ubiquitous in all living organisms, including animals, plants, insects, and microbes. It plays important roles in xenobiotic detoxification, and pheromone degradation, neurogenesis and regulating development. Previous studies mainly used Dipteran Drosophila and mosquitoes as model organisms to investigate the roles of the insect COEs in insecticide resistance. However, genome-wide characterization of COEs in phytophagous insects and comparative analysis remain to be performed.

RESULTS

Based on the newly assembled genome sequence, 76 putative COEs were identified in Bombyx mori. Relative to other Dipteran and Hymenopteran insects, alpha-esterases were significantly expanded in the silkworm. Genomics analysis suggested that BmCOEs showed chromosome preferable distribution and 55% of which were tandem arranged. Sixty-one BmCOEs were transcribed based on cDNA/ESTs and microarray data. Generally, most of the COEs showed tissue specific expressions and expression level between male and female did not display obvious differences. Three main patterns could be classified, i.e. midgut-, head and integument-, and silk gland-specific expressions. Midgut is the first barrier of xenobiotics peroral toxicity, in which COEs may be involved in eliminating secondary metabolites of mulberry leaves and contaminants of insecticides in diet. For head and integument-class, most of the members were homologous to odorant-degrading enzyme (ODE) and antennal esterase. RT-PCR verified that the ODE-like esterases were also highly expressed in larvae antenna and maxilla, and thus they may play important roles in degradation of plant volatiles or other xenobiotics.

CONCLUSION

B. mori has the largest number of insect COE genes characterized to date. Comparative genomic analysis suggested that the gene expansion mainly occurred in silkworm alpha-esterases. Expression evidence indicated that the expanded genes were specifically expressed in midgut, integument and head, implying that these genes may have important roles in detoxifying secondary metabolites of mulberry leaves, contaminants in diet, and odorants. Our results provide some new insights into functions and evolutionary characteristics of COEs in phytophagous insects.

The small heat shock protein (sHSP) genes in the silkworm, Bombyx mori, and comparative analysis with other insect sHSP genes

Background

Small heat shock proteins (sHSPs) are products of heat shock response and of other stress responses, and ubiquitous in all three domains of life, archaea, bacteria, and eukarya. They mainly function as molecular chaperones to protect proteins from being denatured in extreme conditions. Study on insect sHSPs could provide some insights into evolution of insects that have adapted to diverse niches in the world.

Results

Taking advantage of the newly assembled genome sequence, we performed a genome-wide analysis of the candidate sHSP genes in the silkworm, Bombyx mori. Based on known silkworm sHSP sequences, we identified 16 silkworm sHSP genes. Most of them are distributed on two silkworm chromosomes 5 and 27, respectively. 15 of 16 silkworm sHSPs have expression evidence. The comparative analysis of insect sHSPs from B. mori, Drosophila melanogaster, Apis mellifera, Tribolium castaneum, and Anopheles gambiae revealed that there is only one orthologous cluster whereas remaining clusters are species-specific on the phylogenetic tree. This suggested that most of sHSPs might have diverged in function across insects investigated. In addition, the data presented in this study also revealed that sHSPs in the insect orthologous cluster are highly conserved in both sequence and expression pattern. In sum, insect sHSPs show a completely different evolutionary pattern from that found in vertebrate sHSPs.

Conclusion

B. mori has the largest number of insect sHSP genes characterized to date, including 16 genes. The inference that most species-specific sHSPs might have diverged in function across insects investigated will help us understand the adaptability of these insects to diverse environments.

The odorant binding protein gene family from the genome of silkworm, Bombyx mori

Background

Chemosensory systems play key roles in the survival and reproductive success of insects. Insect chemoreception is mediated by two large and diverse gene superfamilies, chemoreceptors and odorant binding proteins (OBPs). OBPs are believed to transport hydrophobic odorants from the environment to the olfactory receptors.

Results

We identified a family of OBP-like genes in the silkworm genome and characterized their expression using oligonucleotide microarrays. A total of forty-four OBP genes were annotated, a number comparable to the 57 OBPs known from Anopheles gambiae and 51 from Drosophila melanogaster. As seen in other fully sequenced insect genomes, most silkworm OBP genes are present in large clusters. We defined six subfamilies of OBPs, each of which shows lineage-specific expansion and diversification. EST data and OBP expression profiles from multiple larvae tissues of day three fifth instars demonstrated that many OBPs are expressed in chemosensory-specific tissues although some OBPs are expressed ubiquitously and others exclusively in non-chemosensory tissues. Some atypical OBPs are expressed throughout development. These results reveal that, although many OBPs are chemosensory-specific, others may have more general physiological roles.

Conclusion

Silkworms possess a number of OBPs genes similar to other insects. Their expression profiles suggest that many OBPs may be involved in olfaction and gustation as well as general carriers of hydrophobic molecules. The expansion of OBP gene subfamilies and sequence divergence indicate that the silkworm OBP family acquired functional diversity concurrently with functional constraints. Further investigation of the OBPs of the silkworm could give insights in the roles of OBPs in chemoreception.

Construction of a full-length cDNA Library from Chinese oak silkworm pupa and identification of a KK-42-binding protein gene in relation to pupa-diapause termination

In this study we successfully constructed a full-length cDNA library from Chinese oak silkworm, Antheraea pernyi, the most well-known wild silkworm used for silk production and insect food. Total RNA was extracted from a single fresh female pupa at the diapause stage. The titer of the library was 5 × 10⁵ cfu/ml and the proportion of recombinant clones was approximately 95%. Expressed sequence tag (EST) analysis was used to characterize the library. A total of 175 clustered ESTs consisting of 24 contigs and 151 singlets were generated from 250 effective sequences. Of the 175 unigenes, 97 (55.4%) were known genes but only five from A. pernyi, 37 (21.2%) were known ESTs without function annotation, and 41 (23.4%) were novel ESTs. By EST sequencing, a gene coding KK-42-binding protein in A. pernyi (named as ApKK42-BP; GenBank accession no. FJ744151) was identified and characterized. Protein sequence analysis showed that ApKK42-BP was not a membrane protein but an extracellular protein with a signal peptide at position 1-18, and contained two putative conserved domains, abhydro_lipase and abhydrolase_1, suggesting it may be a member of lipase superfamily. Expression analysis based on number of ESTs showed that ApKK42-BP was an abundant gene in the period of diapause stage, suggesting it may also be involved in pupa-diapause termination.

A genomewide survey of homeobox genes and identification of novel structure of the Hox cluster in the silkworm, Bombyx mori

Homeobox genes encode transcriptional factors that play crucial roles in a variety of developmental pathways from unicellular to multicellular eukaryotes. We have identified 102 homeobox genes in the typical insect of Lepidoptera, Bombyx mori, based on the newly assembled genome sequence with 9X coverage. These identified homeobox genes were categorized into nine classes including at least 74 families. The available ESTs and microarray data at present confirmed that more than half of them were expressed during silkworm developmental processes. Orthologs of pb, zen and ftz were newly identified in the Bombyx Hox cluster on chromosome 6. Interestingly, a special group of 12 tandemly duplicated homeobox genes was found located between Bmpb and Bmzen in the Bombyx Hox cluster, suggesting that Hox cluster might have experienced a lineage-specific expansion in the silkworm. A detailed analysis on genome data reveals that a split exists between Bmlab and Bmpb. Our data provide valuable information for future research on the development and evolution of silkworm.

The UDP-glucosyltransferase multigene family in Bombyx mori

Background

Glucosidation plays a major role in the inactivation and excretion of a great variety of both endogenous and exogenous compounds. A class of UDP-glycosyltransferases (UGTs) is involved in this process. Insect UGTs play important roles in several processes, including detoxication of substrates such as plant allelochemicals, cuticle formation, pigmentation, and olfaction. Identification and characterization of Bombyx mori UGT genes could provide valuable basic information for this important family and explain the detoxication mechanism and other processes in insects.

Results

Taking advantage of the newly assembled genome sequence, we performed a genome-wide analysis of the candidate UGT family in the silkworm, B. mori. Based on UGT signature and their similarity to UGT homologs from other organisms, we identified 42 putative silkworm UGT genes. Most of them are clustered on the silkworm chromosomes, with two major clusters on chromosomes 7 and 28, respectively. The phylogenetic analysis of these identified 42 UGT protein sequences revealed five major groups. A comparison of the silkworm UGTs with homologs from other sequenced insect genomes indicated that some UGTs are silkworm-specific genes. The expression patterns of these candidate genes were investigated with known expressed sequence tags (ESTs), microarray data, and RT-PCR method. In total, 36 genes were expressed in tissues examined and showed different patterns of expression profile, indicating that these UGT genes might have different functions.

Conclusion

B. mori possesses a largest insect UGT gene family characterized to date, including 42 genes. Phylogenetic analysis, genomic organization and expression profiles provide an overview for the silkworm UGTs and facilitate their functional studies in future.

Identification and analysis of Toll-related genes in the domesticated silkworm, Bombyx mori

Silkworm (Bombyx mori), a model system for Lepidoptera, has contributed enormously to the study of insect immunology especially in humoral immunity. But little is known about the molecular mechanism of immune response in the silkworm. Toll receptors are a group of evolutionarily ancient proteins, which play a crucial role in the innate immunity of both insects and vertebrates. In human, Toll-like receptors (TLRs) are the typical pattern recognition receptors for different kinds of pathogen molecules. Toll-related receptors in Drosophila, however, were thought to function as cytokine receptors in immune response and embryogenesis. We have identified 11 putative Toll-related receptors and two Toll analogs in the silkworm genome. Phylogenetic analysis of insect Toll family and human TLRs showed that BmTolls is grouped with Drosophila Tolls and Anopheles Tolls. These putative proteins are typical transmembrane receptors flanked by the extracellular leucine-rich repeat (LRR) domain and the cytoplasmic TIR domain. Structural prediction of the TIR domain alignment found five stranded sheets and five helices, which are alternatingly joined. Microarray data indicated that BmToll and BmToll-2 were expressed with remarkable enrichment in the ovary, suggesting that they might play a role in the embryogenesis. However, the enriched expression of BmToll-2 and -4 in the midgut suggested that the proteins they encode may be involved in immune defense. Testis-specific expression of BmToll-10 and -11 and BmToLK-2 implies that these may be involved in sex-specific biological functions. The RT-PCR results indicated that 10 genes were induced or suppressed with different degrees after their immune system was challenged by different invaders. Expression profiles of BmTolls and BmToLKs reported here provide insight into their role in innate immunity and development.

Identification and expression pattern of the chemosensory protein gene family in the silkworm, Bombyx mori

Insect chemosensory proteins (CSPs) as well as odorant-binding proteins (OBPs) have been supposed to transport hydrophobic chemicals to receptors on sensory neurons. Compared with OBPs, CSPs are expressed more broadly in various insect tissues. We performed a genome-wide analysis of the candidate CSP gene family in the silkworm. A total of 20 candidate CSPs, including 3 gene fragments and 2 pseudogenes, were characterized based on their conserved cysteine residues and their similarity to CSPs in other insects. Some of these genes were clustered in the silkworm genome. The gene expression pattern of these candidates was investigated using RT-PCR and microarray, and the results showed that these genes were expressed primarily in mature larvae and the adult moth, suggesting silkworm CSPs may be involved in development. The majority of silkworm CSP genes are expressed broadly in tissues including the antennae, head, thorax, legs, wings, epithelium, testes, ovaries, pheromone glands, wing disks, and compound eyes.

Identification and expression pattern of Bmlark, a homolog of the Drosophila gene lark in Bombyx mori

Two Bombyx mori isoforms of the gene lark, which is shown to play an important role in Drosophila circadian rhythms, were identified and named Bmlark-PA and Bmlark-PB, respectively. Bmlark-PA consists of 5 exons and encodes a protein of 343 amino acid residues which contains 3 functional domains: two RRM (RNA recognization motif) domains and an RTZF (retroviral-type zinc finger) and shares 72% identity with the Drosophila gene lark at the amino acid level. Bmlark-PB lacks the sequence between 118 and 791 nt of Bmlark-PA and codes for a protein of 68 amino acid residues, which contains no distinct functional domains. Alignments of the cDNAs of Bmlark to the genomic draft sequence of B. mori showed that the gene Bmlark had a single copy in the genome, suggesting that an alternative splicing mechanism occurs in the gene Bmlark. RT-PCR analysis indicated that Bmlark-PA was expressed only in late pupae and adult but Bmlark-PB was broadly expressed in many tissues and throughout the developmental stages from embryo to adult.

High-level expression of basic fibroblast growth factor in transgenic soybean seeds and characterization of its biological activity

The glycinin G1 gene encodes a soybean seed storage protein accumulating at a high level. We have used the G1 promoter to confer seed-specific expression of human basic fibroblast growth factor (bFGF) in transgenic soybeans. The coding region of 18 kDa bFGF was fused to the promoter or promoter-signal peptide sequence of G1 gene, and transferred into soybean. Analysis of transgenic plants demonstrated that bFGF transcript or protein was confined to the seeds. The highest level of bFGF accumulation in the seeds reached up to 2.3% of total soluble protein. The soybean-derived bFGF was biologically active as confirmed by its mitogenic activity on Balb/c 3T3 cells, and exhibited other properties identical to native bFGF. We also observed a seed-specific expression of beta-glucuronidase driven by the G1 promoter. These results indicated that the G1 promoter contains essential cis-elements for seed-specific expression, and thus can be used for expression of pharmaceutical proteins in soybean seeds.

EST-based profiling and comparison of gene expression in the silkworm fat body during metamorphosis

The fat body plays key roles in metabolism and sustenance of growth throughout the life of a silkworm, and thus represents a model tissue for studying development and metamorphosis. Analysis of 18,480 ESTs derived from larval and pupal fat body cDNA libraries allowed characterization of gene expression patterns in the fat body during metamorphosis. By Phrap assembling, 6,814 estimated transcription units (TUs) were generated, 2,673 of which contained 60% of the total ESTs and represented 1,366 distinctive known genes. These genes were classified into 14 categories based on their known or putative functions, and most were found to be involved in metabolism and cell defense. Further comparative analysis of the expression profiles revealed that the gene expression patterns in the larval fat body strikingly differed from those in the pupal fat body. From this, we identified a subset of genes potentially associated with metamorphic events such as the formation or destruction of specific tissues, and simultaneously confirmed the stage-specific expression patterns of several identified genes using RT-PCR examination. This work will provide a valuable resource for studying regulatory mechanisms associated with fat body developmental changes and silkworm metamorphosis.

Simple sequence repeat-based consensus linkage map of Bombyx mori

We established a genetic linkage map employing 518 simple sequence repeat (SSR, or microsatellite) markers for Bombyx mori (silkworm), the economically and culturally important lepidopteran insect, as part of an international genomics program. A survey of six representative silkworm strains using 2,500 (CA)n- and (CT)n-based SSR markers revealed 17-24% polymorphism, indicating a high degree of homozygosity resulting from a long history of inbreeding. Twenty-nine SSR linkage groups were established in well characterized Dazao and C108 strains based on genotyping of 189 backcross progeny derived from an F(1) male mated with a C108 female. The clustering was further focused to 28 groups by genotyping 22 backcross progeny derived from an F(1) female mated with a C108 male. This set of SSR linkage groups was further assigned to the 28 chromosomes (established linkage groups) of silkworm aided by visible mutations and cleaved amplified polymorphic sequence markers developed from previously mapped genes, cDNA sequences, and cloned random amplified polymorphic DNAs. By integrating a visible mutation p (plain, larval marking) and 29 well conserved genes of insects onto this SSR-based linkage map, a second generation consensus silkworm genetic map with a range of 7-40 markers per linkage group and a total map length of approximately 3431.9 cM was constructed and its high efficiency for genotyping and potential application for synteny studies of Lepidoptera and other insects was demonstrated.

[Study on location of QTLs controlling cocoon traits in silkworm]

On the basis of the molecular linkage map, mapmaker software QTLMapper 2.0 was used to analyze the QTLs effect of the whole cocoon weight,cocoon shell weight, ratio of cocoon shell and pupa weight of domestic silkworm. For these four cocoon quantitative traits, 7, 6, 2 and 8 effective QTLs were detected and mapped to 7, 5, 2 and 7 linkage groups, respectively. Complicated epistatic effects were found involved in the genetic variation of the whole cocoon weight and cocoon shell weight. For the whole cocoon weight, there were three pairs of QTLs with significant additive by additive interactions, in which, one pair had significant additive by dominance and dominance by dominance interactions. Whereas significant dominance were detected for three QTLs and significant additive effects one QTL had. For the cocoon shell weight, significant genetic effects, including epistatic effects were found for one pair of QTLs, significant dominance by dominance interaction for another pair of QTLs; one QTL had significant dominance and another QTL had additive by additive interaction. The ratio of cocoon shell and the pupa weight were controlled mainly by additive or dominance effects. No interaction between QTL was found for the ratio of cocoon. Most QTLs, associated with the pupa weight, had negative dominance effects. Only significant additive by additive interaction was found between one pair of QTLs. The 2nd, 3rd, 4th, 11th, 13th, 24th, 34th, 37th, and 40th linkage groups are the common chromosomal regions harboring QTLs of two or more cocoon quantitative traits. There are identical QTL or chromosomal region for the whole cocoon weight and cocoon shell weight, indicating they can be simultaneously improved by utilizing epistatic effects in breeding.

[Pridiction of the Sex-effects of the Cocoon Quality Characters in Silkworm.]

In this paper , the sex-effects of the cocoon quality characters in silkworm was predicted with Mixed linear model úThe fact that the probability of effect variance and predictability of random gender of whole cocoon weight, cocoon shell weight, ratio of cocoon shell and pupa weight reached a level of extreme significance showed that the gender effect of the four traits was extremely significant, which matched with the reality completely. The predictive values of gender effect of the four traits of female(male) were 0.248g (-0.247g), 2.423cg(-2.394)cg, -1.976%(1.992%) and 0.224g(-0.223g) respectively. Each trait showed single peak distribution after adjusting by sex-effects, which fitted for the request that quantitative traits should show continuously normal standard distribution if QTL analysis was taken.

[Three Bombyx mori genes, chi, gluE and fruA, encode proteins homologous to microorganism and primary analysis of horizontal gene transfer]

According to the analysis of large scale EST sequencing of silkworm, Bombyx mori, we found that chi, glue and fruA of silkworm have very high homology at amino acid level and closely phylogenetic relative with that of microorganism, but lower similarity with genes of eelworm (Caenorhabditis elegans), fruitfly (Drosophila melanogaster), mosquito (Anopheles gambiae) and other relative insects, respectively. It indicates that each of them is likely to have common ancestor with that of microorganism. Namely, microbial genes were likely transferred to silkworm by horizontal gene transfer, instead of the vertical inheritance in evolutionary manner.

[Construction of AFLP molecular markers linkage map and localization of green cocoon gene in silkworm (Bombyx mori)]

Based on an improved method of AFLP, AFLP markers were employed for construction of a linkage map and localization of Gc gene used a set of 44 backcross lines( BC1) of silkworm ( Bombyx mori) as a mapping population. In this work, all together 3 956 bands were obtained by 28 pairs of primers and 141.3 bands each primer pair on average. Among them 2 836 bands were in good agreement with the segregation pattern. A total of 1 018 (25.7%) polymorphic AFLP markers were detected. The 693 (68.1%) of polymorphic markers with 1:1 segregation ratio ( P < or = 0.05) were obtained. Furthermore,The analytical model was based on the backcross type and the parameters were set as following: LOD = 3.0, maximum recombination value of 0. 20 and use the command ' group', 'compare', 'try', 'map' and 'ripple' to construct the linkage maps. 407 of the 693 loci were chi2 tested in agreement with 1:1 segregation were divided into 33 linkages by Mapmaker/Exp(Version 3.0), with a total map distance of 3 676.7 cM and a mean distance of 9.1 cM between markers. The morphological gene Gc was located between L-P4T6-107 and L-PT6T4-84 on linkage group 22. In addition, 286 markers were not included in the linkage groups. The efficiency of loci mapping was 58.7%. Among the 33 linkage groups, the morphological marker Gc classically localized on linkage group 15 was relocated on linkage group 22 on the map, suggesting that this molecular linkage group corresponds to linkage group 15 on the linkage map based on morphological characters. All these have laid an important base for the marker assisted breeding of the silkworm.

Mining single nucleotide polymorphisms from EST data of silkworm, Bombyx mori, inbred strain Dazao

We made use of 81,635 expressed sequence tags (ESTs) derived from 12 different cDNA libraries of the silkworm, Bombyx mori, inbred strain Dazao (P50), to identify high-quality candidate single nucleotide polymorphisms (SNPs). By PHRAP assembling, 12,980 contigs containing 11,537 contigs assembled by more than one read were obtained, and 101 candidate SNPs and 27 single base insertions/deletions were identified from 117 contigs assembled from 1576 high-quality reads base-called with PHRED and screened on the basis of the neighborhood quality standard (NQS). Simultaneously, we also predicted 40 SNPs in coding regions (cSNPs), of which 26 were predicted to lead to amino acid non-synonymous variations and 14 synonymous substitutions. Also, the 1.66:1 ratio of transition/transversion is different from that of other insects. As the first SNP analysis of a Lepidoptera, B. mori, the single nucleotide polymorphic density is estimated to be 1.3 x 10(-3) by sequence diversity. This analysis shows that expressed sequences from multiple libraries may provide an abundant source of comparative reads to mine for cSNPs from the silkworm genome.

[Effects of burn on synthesis and secretion of endothelin-1 in rat paraventricular nucleus of hypothalamus]

AIM AND METHODS

In order to investigate the pathophysiological role of ET-1 in paraventricular nucleus of hypothalamus (PVH) under burn, changes in synthesis and secretion of endothelin-1 (ET-1) in PVH after burn were observed by in situ hybridization and immunohistochemistry. The intensity of ET-1 mRNA and ET-1-immunoreactivity (ET-1-ir) were quantized by image analysis.

RESULTS

Compared with the control group (sham burn, 100% +/- 25%), no significant change in the intensity of ET-1 mRNA positive hybridization signal in PVH was found at 15 min postburn, while the intensity increased significantly both at 60 min (138% +/- 26%, P < 0.05) and at 180 min postburn (167% +/- 18%, P < 0.01). Intensity of ET-1-ir in the neurons in PVH decreased significantly at 15 min postburn to 6.3% +/- 1.5% of the control (P < 0.01) and gradually recovered to 23.1% +/- 2.9% and to 44.1% +/- 3.8% at 60 min and 180 min postburn respectively, while still significantly lower than that in control (P < 0.01).

CONCLUSION

The results demonstrated that the synthesis and secretion of ET-1 in rat PVH increased significantly after burn in rats, suggesting that ET-1 in PVH played an important pathophysiological role under burn.

[Effect of scald on gene transcription and content of endothelin-1 in supraoptic nucleus of rat hypothalamus]

Endothelin-1 (ET-1) gene transcription and endothelin-1-immunoreactivity (ET-1-ir) in the supraoptic nucleus (SON) of rat hypothalamus were respectively observed by in situ hybridization and immunohistochemistry after scald. Intensity of ET-1 mRNA and endothelin-1-immunoreactivity (ET-1-ir) was quantified by image analysis. Compared with the control (sham scald) group, no significant change in the intensity of ET-1 mRNA positive hybridization signals in SON was found 15 min post-scald, while there was a 35.1% increase in the positive hybridization signal intensity 60 min post-scald (P<0.05) and a 62.4% increase 180 min post-scald (P<0.01). The content of ET-1-ir in SON decreased significantly to 8.5% of the control 15 min post-scald (P<0.01), and gradually recovered to 31.5% and 52.4% of the control 60 min and 180 min post-scald respectively, though still significantly lower than the control (P<0.01). Pre- and post-scald ET-1 gene transcription in rat hypothalamus was also measured by Northern blot hybridization. No significant difference in the quantity of ET-1 mRNA was found between 15 min post-scald data and those of the control. The quantity increased to a significantly higher level 60 min post-scald (P<0.05) and further increased to 2.5 creased to 2.5 fold of the control 180 min post-scald (P<0.05). In addition, the Northern blot hybridization showed that the post-scald size of ET-1 mRNA remained unchanged despite of the increase in quantity. In view of the neuroendocrine role of SON, the changes in ET-1 mRNA and ET-1-ir in SON resulting from scald suggest that ET-1 may play an important role in neuroendocrine reactions following scald.

[Construction of silkworm RAPD molecular linkage map]

In this research, a RAPD linkage map of Bombyx mori was constructed with Dazao/C108 and their F2 generation. The map consists of 182 RAPD loci, of which 103 loci come from Dazao and from the first 23 linkage groups and the other 79 loci come from C108 and form the second 16 linkage groups. This map covered a total genetic distance of over 1,148.3 cM (centimorgan). It could be integrated with the SADF map of the same materials constructed in our laboratory and the corresponding RFLP linkage map.