Continuous Production of Silkworm Polyvoltine Strain Eggs by Ideal Analogs of Diapause Hormone

滞育激素（DH）是一种神经肽激素，是一种24个氨基酸的肽酰胺，负责诱导家蚕的胚胎滞育。DH或其类似物是一种新的化学制剂，可用于长期保存蚕卵的多伏特菌株。为了开发一些具有活性的DH类似物，我们化学合成了100多种DH片段类似物，并测试了它们的滞育诱导卵活性。结果表明，C端和C端五肽序列FXPRL的修饰对DH的生物活性表达至关重要。因此，c端六肽酰胺似乎是DH的激动剂。为了获得一种亲脂性和可渗透的新类DH肽，我们利用有机溶剂从雄性成虫头部提取DH活性物质。对活性物质进行了纯化，并分离出其中一种活性物质。分离得到的物质为肽，分子量约为10K，其n端氨基酸测序结果显示Val、Ala和pro含量较高。该肽的生物活性较弱，但具有抗DH降解的保护作用。DH基因结构为6个外显子被5个内含子打断，在食管下神经节的12个神经分泌细胞中表达。卵的孵育温度严格影响该基因的表达，说明滞育的环境调控是通过DH基因表达介导的。将化学合成的DH或其片段注射到蛹中，得到滞育卵。这些卵积累了大量的山梨醇和丙氨酸作为自然滞育卵。因此，DH制剂是一种很有前途的化学调节剂，可以长期保存多伏特家蚕品系的卵。

A neuropeptide hormone, diapause hormone (DH) is a 24 amino acid peptide amide which is responsible for induction of embryonic diapause of the silkworm, Bombyx mori. DH or its analog is a novel chemical agent to be useful for long term preservation of eggs of the polyvoltine strain of the silkworm. In order to develop some active analog of DH,we chemically synthesized more than 100 species of DH fragment analogs, and tested their diapause egg inducing activity. The result led con-clusions that the amidation of C terminus and the C-terminal pentapeptide sequence, FXPRL, are essential for expression of biological activity of DH.Thus, the C-terminal hexa peptide amide seemed to be an agonist of DH.To obtain a new DH-like peptide which is lipophilic and permeable through integment of silkworm pupae, we extracted DH active substances from male adult heads by using an organic solvent. The active materials were purified, and one of them was isolated. The isolated substance was a peptide with a MW of about 10K,and its N-terminal amino acid sequencing showed high content of Val, Ala andPro. The peptide was weak in biological activity, but acted as a protectant against DH degradation.DH gene was organized with 6 exons interrupted by 5 introns, and was expressed in 12 neurosecretory cells of suboesophageal ganglion. The incubation temperarture of eggs strictly affected the expression of the gene, which indicates that the environmental regulation of diapause is mediated through DH gene expression.The chemically synthesized DH or its fragments was injected into pupae, by which treatment diapause eggs were obtained. These eggs accumulated much amounts of sorbitol and alanine as the natural diapause eggs. Thus, the DH agents are promising chemical regulators for long term preservation of eggs of polyvoltine strains of the silkworm.