• International Journal of Industrial Entomology and Biomaterials
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• v.5 no.1
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• pp.1-12
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• 2002

Ecophysiologically diapause represents a syndrome of physiological and biochemical characteristics, all of which ensure survival during a long period of dormancy. Since, silkworm enters diapause as embryo at the early embryonic stage, the duration of egg life depends on the duration of embryonic diapause. The nature of diapause in silkworm, Bombyx mori, is primarily determined by genetic characters and endocrinologicnl mechanisms, mediated by environmental factors such as temperature and photoperiod. Hibernating potency value besides nucleic acid and carbohydrate metabolism, production and utilization of sorbitol are also equally responsible for induction, initiation, determination, maintenance and termination of diapause. Embryonic diapause in Bombyx moir, induced by active secretion of sub-oesophageal ganglion is attributed to hormonal system and metabolic adjustment, which serves to bring about a new physiological state. Metabolic conversion of trehalose to glycogen at induction, glycogen to sorbitol at initiation and sorbitol to glycogen at termination of diapause is correlated and in each metabolic shift a key enzyme becomes active in response to hormonal and environmental stimulation. An attempt has been made in this review article to discuss briefly the nature of embryonic diapause, influence of various factors on diapause nature, hormonal mechanism of diapause besides biochemical composition of egg, nucleic acid and carbohydrate metabolism, production and utilization of sorbitol in relation to induction, determination, maintenance, initiation and termination of diapause in the silkworm, Bombyx mori.

• International Journal of Industrial Entomology and Biomaterials
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• v.15 no.2
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• pp.165-169
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• 2007

A differential specific pattern of variation in the metabolism of protein and cholesterol was noticed in non -diapause and diapause eggs due to the significant differences in embryonic development. The rate of metabolism was different due to specific demands of such metabolites during active embryogenesis and maintenance of diapause respectively. In general, the metabolic rate was found to be accelerated in non- diapause eggs just after egg deposition, while it was very slow in diapause eggs. When the diapause eggs were treated with hydrochloric acid within 16-20 hrs, the rate of turnover was found to very similar to non- diapause eggs, though the base level of protein and cholesterol was recorded to be different.

• Journal of Life Science
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• v.6 no.3
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• pp.171-177
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• 1996

It was carried out to find the carbohydrate metabolism for the glycogen utilization and the effects of low temperature(1$\circ$C, 5$\circ$C)on embryonic development of the silkworm, Bombyx mori L. The content of sorbitol and glycerol in the chillihg eggs stored at 5$\circ$C or 1$\circ$C on 24 hours after oviposition showed the highest level on the 50th day. After that, the corresponding value in the eggs stored at 5$\circ$C were decreased, and the value in the eggs stored at 1$\circ$C maintained the similar level. The trehalose level was rapidly increased on 50$\sim$60th day or thereabouts, and then, it was accumulated. When the eggs stored at low temperature were tranaferred and developed the embryo at 25$\circ$C, sorbitol and glycerol were respectively changed to glycogen. Futhemore, the content of trehalose and glucose showed specific of patterns with each embryonic stage at low temperature. With the aforementioned results, the intemediary metabolism of carbohydrate was discussed with regard to embryonic development of non-diapause eggs of silkworms.

• Proceedings of the Korean Society of Sericultural Science Conference
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• 1997.06a
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• pp.51-72
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• 1997

Diapause hormone (DH) is a neuropeptide hormone which is secreted from the suboesophageal ganglion (SG) and is responsible for induction of embryonic diapause of the silkworm, Bombyx mori. DH is isolated from SGs and determined to be a 24 amino acid peptide amide. The cDNA encodes the polyprotein precursor from which DH, pheromone biosynthesis activating neuropeptide (PBAN) and three other neuropeptides are released and become matured. The C-terminal FXPRL-NH2 sequence of DH is essential but not sufficient for expression of full activity. Recently, we have isolated a unique hydrohobic peptide (VAP peptide) with a slight diapause egg induceing activity from organic solvent extracts of the male adult heads of the silkworm. The VAP peptide itself has no diapause inducing activity, but enhances DH activity through reducing ED50 value and the threshold concentration of DH. The DH-PBAN gene is composed of 6 exons interrupted by 5 introns and is expressed in 12 neurosecretory cells of the SG. The incubation of eggs at 25$^{\circ}C$, which induces embryonic diapause in the progeny, caused DH-PBAN mRNA content to increase at 5 different stages in the life cycle. By contrast, a 15$^{\circ}C$ incubation only induced expression of the gene at the late phrase adult stage. The temperature-controlled expression of DH-PBAN gene is closely correlated to the incidence of diapause, indicating that DH-PBAN gene expression is the initial event leading to diapause induction. DH acts to stimulate trehalase activity in developing ovary to bring about hyprglycogenism in mature eggs, a prerequisite metabolism for diapause initiation. Using in vivo and in vitro systems, DH is clearly shown to induce trehalase gene expression in developing ovaries. New protein synthesis is not needed for this process, but a Ca2+-dependent proteinkinase seems to be involved. Quite recently, we have sucessfully applied a new and potent trehalase inhibitor (Trehazoline) to reudce glycogen content in developing ovaries. The eggs deficient in glycogen were also able to enter diapause as the natural eggs do, so that we could provide the new egg system to reconsider the diapause associated metabolism other than the glycogen-sorbitol metabolic system.

• International Journal of Industrial Entomology and Biomaterials
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• v.9 no.1
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• pp.117-121
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• 2004

The patterns of diapause-associated proteins of silkworm eggs were analyzed by two-dimensional (2-D) gel electrophoresis. Among the hundreds of spots on the 2-D gels, at least two proteins were considered to be associated with diapause. A protein, spot 4, with an approximate molecular weight of 38 kDa and pI 6.1 was observed in the HCI-treated, cold-treated, and diapause eggs, respectively. Spot 4 was undetectable in unfertilized eggs and non-diapause eggs at two days after oviposition, suggesting that this protein may be associated with the entrance to diapause. A protein, spot 11, with an approximate molecular weight of 21 kDa and pI of 61 was detected in the unfertilized, HCl-treated, and cold-treated eggs, respectively, after oviposition by normal moths. In diapausing eggs, a protein corresponding to spot 11 was observed in 3-, 5-, and 30-day-old eggs, while the protein was not detected one-day-old eggs. The protein corresponding to spot 11 was not detected in unfertilized and non-diapause eggs obtained from subesophabeal ganglion (SG)-extirpated moths either. Spot 11 was also considered to be a diapause specific protein, which occurred at only early embryonic stage under the control of diapause-downregulated gene.

• International Journal of Industrial Entomology and Biomaterials
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• v.43 no.2
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• pp.37-44
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• 2021

Mulberry silkworm is classified into uni, bi and multivoltine based on the frequency of diapause incidence. The variation in the incidence of diapause in bivoltine silkworm provides a unique opportunity to study the process of evolution of adaptive plasticity towards seasonal variations. The diapause expression in bivoltine silkworm is highly variable and is determined by environmental factors experienced by the maternal generation. Diapause in natural populations is functionally associated with the overwintering mechanism that facilitates survival in harsh winter conditions. In contrast, under standard commercial rearing conditions, the domesticated bivoltine silkworm is known to enter diapause in every generation. This paper presents a short review of the literature dealing with the role of temperature, photoperiod, diapause hormone and its receptor in diapause induction. Also, we briefly review the incidence of non-diapause eggs in bivoltine silkworm under controlled conditions.

• International Journal of Industrial Entomology and Biomaterials
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• v.9 no.1
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• pp.145-148
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• 2004

As an initial step to define the molecular mechanism of diapause during embryogenesis of the silkworm, Bombyx mori, mRNA transcripts from diapausing eggs and diapause-activated eggs were compared by differential expression using cDNA microarray. Twenty-four individual cDNA clones were identified. Amomg them, ten genes including alcohol dehydrogenase, dead box-l, cytochrome oxidase subunit I and 18 wheeler showed increased expression in the diapause-activated eggs. The rest of fourteen genes showed increased expression in diapausing eggs.

• Journal of Sericultural and Entomological Science
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• v.15 no.2
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• pp.1-7
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• 1973

It was found that the diapause in the silkworm egg is induced by the action of the diapause hormone secreted from the suboesophageal ganglion, and "esterase A" affects protein metabolism in oocyte and egg. In this connection, some changes in protein metabolism of silkworm egg according to embryonic developments could give some information on the diapause, using Ouchterlony Test. Antigenicity of the protein of silkworm egg was detected through antigen-antibody interaction among the extracts of rabbit blood. Furthermore, existence of the specific antigen was also detected according to embryonic development, using the adsorption test. The results were obtained as follows: 1 Detection of antigenicity The antigenicity of silkworm egg was ascertained by inoculating it into a rabbit, but positive results were shown in most of the silkworm eggs tested, whereas the antibody specific to a certain antigen was not detected. 2. Detection of the common antigen It was demonstrated that most of the antigen could incite the common antibodies, but the specific antibody formation was not detected in a few antigens, even though the nonspecific antibody formation was displayed. 3. Detection of the specific antigen It is suggested that there are the specific antigens detectable in each treated eggs by the adsorption test.

• Journal of Sericultural and Entomological Science
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• v.17 no.1
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• pp.31-34
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• 1975

This experiment was carried out to find out whether an electric-shock can hatch the diapause eggs or not. The results obtained are summarized as follows: 1. The electric-shock speeded up the embryonic development in diapausing eggs. 2. The higher hatchability was shown by the electric shock for five seconds. 3. The diapause eggs which had been treated with electric-shock and cold storage were hatched covering 15 to 22 days.

• Proceedings of the Korean Society of Applied Entomolohy Conference
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• 2002.11a
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• pp.110-110
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• 2002