营养和激素对家蝇卵黄发生的影响

本实验通过对家蝇取食量的测定，对家蝇进行不同饲料饲喂后，对其不同发育期的血淋巴、脂肪体及和卵巢的发育及卵黄蛋白含量进行观察测定，结果表明，取食蛋白组家蝇血淋巴、脂肪体和卵巢卵黄蛋白含量均高于奶粉组和对照组；羽化４８ｈ后的血淋巴和脂肪体中卵黄蛋白含量为７．３μｇ／μｌ、３１．９μｇ／头；卵巢卵黄蛋白含量为５５．０μｇ／头；在羽化后７２ｈ血淋巴和脂肪体中卵黄蛋白含量分别为２．９μｇ／μｌ、３２．０μｇ／头；卵巢卵黄蛋白含量为８０．０μｇ／头；脉冲式饲喂家蝇后，体内卵黄蛋白含量明显高于对照组，说明蛋白质饲料在家蝇卵黄发生中起重要作用。激素处理结果证明，ＪＨＡ单独处理及ＪＨＡ和蜕皮素协同处理均能促进卵黄蛋白的合成和摄取，而蜕皮素单独处理没有促进作用。最后对营养和激素对生殖的调控作用进行了讨论。     

The genome of the nematode Pristionchus pacificus encodes putative homologs of RXR/Usp and EcR

Ecdysteroid signaling is an important regulator of arthropod development and reproduction. However, the role of ecdysteroid signaling in another Ecdysozoan animal, the nematode, remains unclear. We report here the identification, cloning, and temporal expression of genes encoding putative homologs of the two nuclear receptor components of the ecdysone receptor, RXR/Usp (NR2B) and EcR (NR1H), in the nematode Pristionchus pacificus. The P. pacificus genes Ppa-pnhr-1 and Ppa-pnhr-2 encode nuclear receptors with strong sequence similarity to RXR/Usp and EcR, respectively. Maximum likelihood analysis incorporating both DNA-binding and ligand-binding domains places the two proteins in the NR2B and NR1H groups with strong bootstrap support. RT-PCR analysis reveals that both Ppa-pnhr-1 and Ppa-pnhr-2 are expressed during larval development and that Ppa-pnhr-1 expression oscillates with the molting cycle. The identification of a putative ecdysone receptor in a nematode amenable to genetic analysis provides a powerful system to investigate the function and evolution of ecdysone receptor signaling in the Nematoda.     

Ecdysteroid hormone titer and its relationship to vitellogenesis in the soft tick, Ornithodoros moubata (Acari: Argasidae)

A blood meal is required for reproduction in most argasid female ticks. The blood meal appears to stimulate an organ in the posterior end to produce a fat body stimulating factor (FSF), which is thought to be an ecdysteroid, to induce vitellogenin (Vg) synthesis. In this study, the relationship of vitellogenesis and ecdysteroids was investigated by measuring Vg and ecdysteroid titers while observing oocyte development and oviposition in mated and virgin females. Oviposition occurred from day 10 after engorgement in mated females and continued up to 40-50 days, whereas egg maturation and oviposition did not occur in virgin females. Vg titers in the hemolymph peaked on day 6 after engorgement and subsequently declined in mated females. Interestingly, Vg synthesis occurred and ovarian development progressed to the development of early vitellogenic oocytes in virgin females but oocyte maturation and oviposition did not occur. Topical application of ecdysteroids induced oviposition in fed virgin females indicating that ecdysteroids may induce oviposition. Concentrations of ecdysteroids for 20 days after engorgement revealed several peaks in mated female whole body extracts, but no peaks in virgin female extracts. In the hemolymph of only mated females, ecdysteroid titers showed two peaks that followed the early peak of ecdysteroids in the whole body on day 4 and 6 after engorgement. In addition, ecdysteroids in the reproductive tissues increased with the development of the ovary in mated females and this increase coincided with the latter peaks of the whole body. These observations indicate that physiological elevation of ecdysteroids accelerate Vg synthesis, and may induce egg maturation and stimulate oviposition in fed mated Ornithodoros moubata females.     

The steroid hormone receptor EcR finely modulates Drosophila lifespan during adulthood in a sex-specific manner

The steroid hormone ecdysone influences Drosophila lifespan. Longevity is extended in mutants deficient for ecdysone synthesis or mutants of the ecdysone receptor (EcR). However, the underlying mechanisms remain unclear. Here we conditionally inactivated EcR by RNA interference or expression of dominant negative forms, using the RU486 inducible system. A mild ubiquitous inactivation of EcR during adulthood was sufficient to slow the aging of male flies, whereas a stronger EcR inactivation decreased longevity. Surprisingly, ubiquitous inactivation of EcR strongly decreased female lifespan. This deleterious effect was suppressed in sterile ovo^D1 mutant females, suggesting that EcR represses a negative signal for lifespan produced in ovaries. These results reveal a complex adult and sex-specific control of lifespan by steroid signalling in Drosophila.     

Assembly of insect hormone enthusiasts at Nasu Highland,Japan: Report of the 3rd International Insect Hormone (21st Ecdysone) Workshop

The 3rd International Insect Hormone (21st Ecdysone) Workshop (IIHW2017) was held in July 2017 at Nasu Highland, Japan. In the 40 years of the workshop's history, this was the first to be held in an Asian country. A total of 109 insect hormone researchers from 18 countries (62 overseas and 47 domestic participants) attended IIHW2017. During the workshop, all participants stayed on‐site at the venue's hotel; this was ideal for fostering communication between participants, in particular, interactions between principal investigators and young scientists. The workshop featured one keynote, 64 oral, and 35 poster presentations spanning molecular biology, cell biology, developmental biology, neurobiology, chemical biology, physiology, and ecology of insect hormones, including ecdysteroids, juvenile hormones, and a variety of neuropeptides. The workshop provided an ideal platform for discussing insect hormone biology using not only the typical genetic model insect, the fruit fly Drosophila, but also a diversity of interesting insects, such as the silkworm, the red flour beetle, the cricket, the dragonfly, the social ant, the bloodsucking tick, and so on. The participants succeeded in sharing the latest knowledge in a wide range of insect hormone research fields and in joining active and constructive scientific discussions.     

Ecdysteroids, juvenile hormone and insect neuropeptides: Recent successes and remaining major challenges

In the recent decade, tremendous progress has been realized in insect endocrinology as the result of the application of a variety of advanced methods in neuropeptidome- and receptor research. Hormones of which the existence had been shown by bioassays four decades ago, e.g. bursicon (a member of the glycoprotein hormone family) and pupariation factor (Neb-pyrokinin 2, a myotropin), could be identified, along with their respective receptors. In control of diurnal rhythms, clock genes got company from the neuropeptide Pigment Dispersing Factor (PDF), of which the receptor could also be identified. The discovery of Inka cells and their function in metamorphosis was a true hallmark. Analysis of the genomes of Caenorhabditis elegans, Drosophila melanogaster and Apis mellifera yielded about 75, 100 and 200 genes coding for putative signaling peptides, respectively, corresponding to approximately 57, 100 and 100 peptides of which the expression could already be proven by means of mass spectrometry. The comparative approach invertebrates-vertebrates recently yielded indications for the existence of counterparts in insects for prolactin, atrial natriuretic hormone and Growth Hormone Releasing Hormone (GRH). Substantial progress has been realized in identifying the Halloween genes, a membrane receptor(s) for ecdysteroids, a nuclear receptor for methylfarnesoate, and dozens of GPCRs for insect neuropeptides. The major remaining challenges concern the making match numerous orphan GPCRs with orphan peptidic ligands, and elucidating their functions. Furthermore, the endocrine control of growth, feeding-digestion, and of sexual differentiation, in particular of males, is still poorly understood. The finding that the prothoracic glands produce an autocrine factor with growth factor-like properties and secrete proteins necessitates a reevaluation of their role in development.     

Suppressed production of methyl farnesoid hormones yields developmental defects and lethality in Drosophila larvae

A long-unresolved question in the developmental biology of Drosophila melanogaster has been whether methyl farnesoid hormones secreted by the ring gland are necessary for larval maturation and metamorphosis. In this study, we have used RNAi techniques to inhibit 3-Hydroxy-3-Methylglutaryl CoA Reductase (HMGCR) expression selectively in the corpora allatal cells that produce the circulating farnesoid hormones. The developing larvae manifest a number of developmental, metabolic and morphogenetic derangements. These defects included the exhibition of an “ultraspiracle” death phenotype at the 1st to 2nd instar larval molt, similar to that exhibited by animals that are null for the farnesoid receptor ultraspiracle. The few larvae surviving past a second lethal period at the 2nd to 3rd instar larval molt, again with “ultraspiracle” phenotype, often became developmentally arrested after either attaining a misformed puparium or after formation of the white pupa. Survival past the “ultraspiracle” lethal phenotype could be rescued by dietary provision of an endogenous dedicated precursor to the three naturally secreted methyl farnesoid hormones. In addition to these developmental and morphogenetic defects, most larvae that survived to the late second instar exhibited a posterior-originating melanization of the tracheal system. These results support the hypothesis that larval methyl farnesoid hormones are necessary for larval survival and morphogenetic transformation through the larval and pupal metamorphic processes.     

Activation of neuroblast proliferation in explant culture of the Drosophila larval CNS

The developmental control of neuroblast proliferation is absolutely required for the assembly and function of the central nervous system. A lethal mutation in trol results in the failure of quiescent neuroblasts to begin division at the appropriate time. I have established a culture system in which quiescent neuroblasts in explants of Drosophila larval CNSs initiate cell division in vitro to normal in vivo levels. This activation requires removal of the CNS for culture after a specific developmental stage and the presence of fetal calf serum or a larval extract in the medium. Either supplement is effective when heat-treated. Substitution of the steroid hormone ecdysone or the non-steroidal ecdysone analog RH5992 for either fetal calf serum or larval extract also results in activation of neuroblast proliferation. Culture of trol^sd CNSs with wildtype larval extract or ecdysone results in the defective neuroblast proliferation phenotype observed in trol mutants in vivo, while culture of wildtype CNSs with trol^sd extract produces normal neuroblast proliferation.     

Morphological changes and patterns of ecdysone receptor B1 immunolocalization in the anterior silk gland undergoing programmed cell death in the silkworm, Bombyx mori

The silk gland is a specific larval tissue of Lepidopteran insects and begins to degenerate shortly before pupation. The steroid hormone ecdysone triggers the stage specific programmed cell death of the anterior silk glands during metamorphosis in the silkworm, Bombyx mori. The anterior silk gland expresses ecdysone receptors, which are involved in regulation processes in response to ecdysone. In this study, the morphological changes, immunohistochemical localization and protein levels of ecdysone receptor B1 (EcR-B1) in the anterior silk gland of B. mori were investigated during programmed cell death. Morphological changes observed during the degeneration process involve the appearance of large vacuoles, probably autophagic vacuoles, which increase in number in pupal anterior silk glands. No macrophages were found in the silk gland during the prepupal and pupal stage unlike in apoptosis, which strongly suggests that programmed cell death of the anterior silk gland is carried out by autophagy. Morphological changes of the silk glands were accompanied by changes in the immunolocalization and protein levels of EcR-B1. The differences in tissue distribution and protein levels of EcR-B1 during the programmed cell death indicate that the receptor plays a major role in the modulation and function of ecdysone activity in Bombyx anterior silk glands. Our results indicate that EcR-B1 expression may be important for the process of programmed cell death in the anterior silk glands.