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Inui T, Sezutsu H, Daimon T. MicroRNA let-7 is required for hormonal regulation of metamorphosis in the silkworm, Bombyx mori. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2022; 145:103784. [PMID: 35533806 DOI: 10.1016/j.ibmb.2022.103784] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 04/28/2022] [Accepted: 05/02/2022] [Indexed: 06/14/2023]
Abstract
The heterochronic microRNA let-7, which was first identified in Caenorhabditis elegans, controls the timing of developmental programs, and let-7 triggers the onset of the juvenile-adult transition in bilaterians. The expression of let-7 is strongly induced during the last larval stage of C. elegans and is highly expressed in the late last instar larvae/nymphs of the fly Drosophila melanogaster and the cockroach Blattella germanica. In the silkworm Bombyx mori, the expression of let-7 remarkably increases in the corpus cardiacum-corpus allatum complex (CC-CA) at the beginning of the last larval instar and is maintained at high levels during this instar. To determine the biological function of let-7 in B. mori, we generated a let-7 knockout line and a transgenic UAS-let-7 line. The let-7 knockout larvae were developmentally arrested in the prepupal stage and became pupal-adult intermediates after apolysis. When let-7 was ubiquitously overexpressed under the transcriptional control of an Actin3-GAL4 driver, developmental timing and growth of larvae were severely impaired in the penultimate (L4) instar, and these larvae underwent precocious metamorphosis from L4. Furthermore, our results showed that reception and signaling of ecdysteroids and juvenile hormones (JHs) normally occurred in the absence of let-7, whereas the biosynthesis of ecdysone and JHs were affected by disruption and overexpression of let-7. Together, the present study demonstrates that let-7 is required for the coordination of the biosynthesis of ecdysone and JH to ensure the developmental transition during the metamorphosis of B. mori.
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Affiliation(s)
- Tomohiro Inui
- Department of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwakecho, Sakyo-ku, Kyoto, 606-8502, Japan
| | - Hideki Sezutsu
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Owashi 1-2, Tsukuba, Ibaraki, 305-8634, Japan
| | - Takaaki Daimon
- Department of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa Oiwakecho, Sakyo-ku, Kyoto, 606-8502, Japan.
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Parthasarathy R, Palli SR. Stage-specific action of juvenile hormone analogs. JOURNAL OF PESTICIDE SCIENCE 2021; 46:16-22. [PMID: 33746542 PMCID: PMC7953018 DOI: 10.1584/jpestics.d20-084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Accepted: 01/08/2021] [Indexed: 06/12/2023]
Abstract
The discovery of juvenile hormones (JH) and their synthetic analogs (JHA) generated excitement and hope that these compounds will replace first- and second-generation insecticides that have not so desirable environmental and human safety profiles. However, JHAs used commercially during the past four decades did not meet these expectations. The recent availability of advanced molecular and histological methods and the discovery of key players involved in JH action provided some insights into the functioning of JHA in a stage and species-specific manner. In this review, we will summarize recent findings and stage-specific action of JHA, focusing on three commercially used JHA, methoprene, hydroprene and pyriproxyfen and economically important pests, the red flour beetle, Tribolium castaneum, and the tobacco budworm, Heliothis virescens, and disease vector, the yellow fever mosquito, Aedes aegypti.
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Affiliation(s)
- Ramaseshadri Parthasarathy
- Department of Entomology, University of Kentucky, College of Agriculture, Food and Environment, Lexington, KY, USA
| | - Subba Reddy Palli
- Department of Entomology, University of Kentucky, College of Agriculture, Food and Environment, Lexington, KY, USA
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Ogihara MH, Hikiba J, Iga M, Kataoka H. Negative regulation of juvenile hormone analog for ecdysteroidogenic enzymes. JOURNAL OF INSECT PHYSIOLOGY 2015; 80:42-47. [PMID: 25907890 DOI: 10.1016/j.jinsphys.2015.03.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 03/02/2015] [Accepted: 03/20/2015] [Indexed: 06/04/2023]
Abstract
Disruption of the appropriate balance between juvenile hormone (JH) and ecdysteroids causes abnormal insect development. The application of a JH analog (JHA) during the early days of the final (fifth) instar induces dauer larvae with low ecdysteroid titers in insects, but the mechanism that underlies the action of JHA remains unclear. In this study, we clarified the negative effects of JHA on ecdysteroidogenic enzymes. JHA application to Bombyx mori larvae during the early stage of the fifth instar suppressed the expression of four enzymes, i.e., neverland (nvd), spook, phantom, and disembodied but not non-molting glossy and shadow. Furthermore, JHA application reduced the amount of 7-dehydrocholesterol, a metabolite produced by Nvd, in both the prothoracic glands and hemolymph, indicating JHA can disrupt ecdysteroidogenic pathway from the first step. Neck ligation resulted in increased nvd expression, whereas JHA application reversed this increase. These results suggest that the endogenous JH represses ecdysteroidogenesis during the early days in final instar larvae. Neck ligation and JHA application had no substantial effects on the expression of a transcription factor, ftz-f1, or a prothoracicotropic hormone receptor, torso; therefore, the inhibitory regulation of JHA may not involve these factors. Further analysis is required to clarify the regulation of JHA in ecdysteroidogenesis, but this study showed that JHA, and probably endogenous JH, can suppress the transcription of four of six ecdysteroidogenic enzymes. This regulation may be essential for maintaining the appropriate balance between JH and ecdysone during insect development.
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Affiliation(s)
- Mari H Ogihara
- Graduate School of Frontier Sciences, The University of Tokyo, Kasiwano-ha 5-1-5, Kashiwa, Chiba 277-8562, Japan.
| | - Juri Hikiba
- Graduate School of Frontier Sciences, The University of Tokyo, Kasiwano-ha 5-1-5, Kashiwa, Chiba 277-8562, Japan
| | - Masatoshi Iga
- Graduate School of Frontier Sciences, The University of Tokyo, Kasiwano-ha 5-1-5, Kashiwa, Chiba 277-8562, Japan
| | - Hiroshi Kataoka
- Graduate School of Frontier Sciences, The University of Tokyo, Kasiwano-ha 5-1-5, Kashiwa, Chiba 277-8562, Japan.
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The POU factor ventral veins lacking/Drifter directs the timing of metamorphosis through ecdysteroid and juvenile hormone signaling. PLoS Genet 2014; 10:e1004425. [PMID: 24945490 PMCID: PMC4063743 DOI: 10.1371/journal.pgen.1004425] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 04/20/2014] [Indexed: 12/22/2022] Open
Abstract
Although endocrine changes are known to modulate the timing of major developmental transitions, the genetic mechanisms underlying these changes remain poorly understood. In insects, two developmental hormones, juvenile hormone (JH) and ecdysteroids, are coordinated with each other to induce developmental changes associated with metamorphosis. However, the regulation underlying the coordination of JH and ecdysteroid synthesis remains elusive. Here, we examined the function of a homolog of the vertebrate POU domain protein, Ventral veins lacking (Vvl)/Drifter, in regulating both of these hormonal pathways in the red flour beetle, Tribolium castaneum (Tenebrionidae). RNA interference-mediated silencing of vvl expression led to both precocious metamorphosis and inhibition of molting in the larva. Ectopic application of a JH analog on vvl knockdown larvae delayed the onset of metamorphosis and led to a prolonged larval stage, indicating that Vvl acts upstream of JH signaling. Accordingly, vvl knockdown also reduced the expression of a JH biosynthesis gene, JH acid methyltransferase 3 (jhamt3). In addition, ecdysone titer and the expression of the ecdysone response gene, hormone receptor 3 (HR3), were reduced in vvl knockdown larvae. The expression of the ecdysone biosynthesis gene phantom (phm) and spook (spo) were reduced in vvl knockdown larvae in the anterior and posterior halves, respectively, indicating that Vvl might influence ecdysone biosynthesis in both the prothoracic gland and additional endocrine sources. Injection of 20-hydroxyecdysone (20E) into vvl knockdown larvae could restore the expression of HR3 although molting was never restored. These findings suggest that Vvl coordinates both JH and ecdysteroid biosynthesis as well as molting behavior to influence molting and the timing of metamorphosis. Thus, in both vertebrates and insects, POU factors modulate the production of major neuroendocrine regulators during sexual maturation. Hormones play major roles in initiating major developmental transitions, such as puberty and metamorphosis. However, how organisms coordinate changes across multiple hormones remains unclear. In this study, we show that silencing the POU domain transcription factor Ventral veins lacking (Vvl)/Drifter in the red flour beetle Tribolium castaneum leads to precocious metamorphosis and an inability to molt. We show that Vvl regulates the biosynthesis and signaling of two key insect developmental hormones, juvenile hormone (JH) and ecdysteroids. Vvl therefore appears to act as a potential central regulator of developmental timing by influencing two major hormones. Because POU factors are known as a major regulator of the onset of puberty, POU factors play a major role during sexual maturation in both vertebrates and insects.
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Kayukawa T, Murata M, Kobayashi I, Muramatsu D, Okada C, Uchino K, Sezutsu H, Kiuchi M, Tamura T, Hiruma K, Ishikawa Y, Shinoda T. Hormonal regulation and developmental role of Krüppel homolog 1, a repressor of metamorphosis, in the silkworm Bombyx mori. Dev Biol 2014; 388:48-56. [DOI: 10.1016/j.ydbio.2014.01.022] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 01/17/2014] [Accepted: 01/26/2014] [Indexed: 10/25/2022]
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Hepat R, Lee D, Kim Y. Juvenile hormone regulates an expression of a late gene encoded in a polydnavirus, Cotesia plutellae bracovirus. Comp Biochem Physiol A Mol Integr Physiol 2013; 165:214-22. [DOI: 10.1016/j.cbpa.2013.03.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2012] [Revised: 03/09/2013] [Accepted: 03/11/2013] [Indexed: 12/17/2022]
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Daimon T, Yago M, Hsu YF, Fujii T, Nakajima Y, Kokusho R, Abe H, Katsuma S, Shimada T. Molecular phylogeny, laboratory rearing, and karyotype of the bombycid moth, Trilocha varians. JOURNAL OF INSECT SCIENCE (ONLINE) 2012; 12:49. [PMID: 22963522 PMCID: PMC3476958 DOI: 10.1673/031.012.4901] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Accepted: 11/04/2011] [Indexed: 05/23/2023]
Abstract
This study describes the molecular phylogeny, laboratory rearing, and karyotype of a bombycid moth, Trilocha varians (F. Walker) (Lepidoptera: Bombycidae), which feeds on leaves of Ficus spp. (Rosales: Moraceae). The larvae of this species were collected in Taipei city, Taiwan, and the Ryukyu Archipelago (Ishigaki and Okinawa Islands, Japan). Molecular phylogenetic analyses revealed that T. varians belongs to the subfamily Bombycinae, thus showing a close relationship to the domesticated silkworm Bombyx mori (L.), a lepidopteran model insect. A laboratory method was developed for rearing T. varians and the time required for development from the embryo to adult was determined. From oviposition to adult emergence, the developmental zero was 10.47 °C and total effective temperature was 531.2 day-degrees, i.e., approximately 30 days for one generation when reared at 28 °C. The haploid of T. varians consisted of n = 26 chromosomes. In highly polyploid somatic nuclei, females showed a large heterochromatin body, indicating that the sex chromosome system in T. varians is WZ/ZZ (female/male). The results of the present study should facilitate the utilization of T. varians as a reference species for B. mori, thereby leading to a greater understanding of the ecology and evolution of bombycid moths.
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Affiliation(s)
- Takaaki Daimon
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan
- National Institute of Agrobiological Sciences, 1–2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan
| | - Masaya Yago
- The University Museum, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Yu-Feng Hsu
- Department of Life Science, National Taiwan Normal University, 88, Ting Chou Rd., Sec 4, Taipei 116, Taiwan
| | - Tsuguru Fujii
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Yumiko Nakajima
- Gene Research Center, University of the Ryukyu, Chihara 1, Nishihara-cho, Okinawa 903-0213, Japan
| | - Ryuhei Kokusho
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Hiroaki Abe
- Department of Biological Production, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Saiwai-cho 3-5-8, Fuchu, Tokyo 183-8509, Japan
| | - Susumu Katsuma
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Toru Shimada
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan
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Tian L, Guo E, Diao Y, Zhou S, Peng Q, Cao Y, Ling E, Li S. Genome-wide regulation of innate immunity by juvenile hormone and 20-hydroxyecdysone in the Bombyx fat body. BMC Genomics 2010; 11:549. [PMID: 20932328 PMCID: PMC3091698 DOI: 10.1186/1471-2164-11-549] [Citation(s) in RCA: 89] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2010] [Accepted: 10/09/2010] [Indexed: 12/20/2022] Open
Abstract
Background Insect innate immunity can be affected by juvenile hormone (JH) and 20-hydroxyecdysone (20E), but how innate immunity is developmentally regulated by these two hormones in insects has not yet been elucidated. In the silkworm, Bombyx mori, JH and 20E levels are high during the final larval molt (4 M) but absent during the feeding stage of 5th instar (5 F), while JH level is low and 20E level is high during the prepupal stage (PP). Fat body produces humoral response molecules and hence is considered as the major organ involved in innate immunity. Results A genome-wide microarray analysis of Bombyx fat body isolated from 4 M, 5 F and PP uncovered a large number of differentially-expressed genes. Most notably, 6 antimicrobial peptide (AMP) genes were up-regulated at 4 M versus PP suggesting that Bombyx innate immunity is developmentally regulated by the two hormones. First, JH treatment dramatically increased AMP mRNA levels and activities. Furthermore, 20E treatment exhibited inhibitory effects on AMP mRNA levels and activities, and RNA interference of the 20E receptor EcR-USP had the opposite effects to 20E treatment. Conclusion Taken together, we demonstrate that JH acts as an immune-activator while 20E inhibits innate immunity in the fat body during Bombyx postembryonic development.
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Affiliation(s)
- Ling Tian
- Key Laboratory of Developmental and Evolutionary Biology, Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China
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Proteomic identification of the silkworm (Bombyx mori L) prothoracic glands during the fifth instar stage. Biosci Rep 2009; 29:121-9. [DOI: 10.1042/bsr20080076] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Although the ecdysteroid of the silkworm had been studied for decades, the proteome of the prothoracic gland, the primary source of ecdysteroid hormones, has not been studied previously. In the present paper, we utilized a proteomic approach to investigate the fifth instar prothoracic gland during the growth and development of the silkworm, Bombyx mori L. The two-dimensional electrophoresis results showed that the majority of proteins were acidic proteins, especially concentrated in the area of 25–65 kDa, with pI values of between 4 and 7, and the difference was not distinct. When compared with Qiufeng (Japanese strain), the interspecific distinction was larger than the intraspecific distinction, and 19 particular spots, excized from the third, fifth and ninth days of p50 (Chinese strain) and Qiufeng were subjected to MALDI-TOF–MS (matrix-assisted laser-desorption ionization–time-of-flight MS) analysis. We sorted them into seven catagories: energetics and/or metabolism, storage proteins, protection, lipid metabolism, signal transduction, cell function and unknown function proteins. Of these proteins, arginine methyltransferase is discussed as playing an important role in regulating the activation of ecdysteroidogenesis via transcription or translation.
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Nakahara Y, Matsumoto H, Kanamori Y, Kataoka H, Mizoguchi A, Kiuchi M, Kamimura M. Insulin signaling is involved in hematopoietic regulation in an insect hematopoietic organ. JOURNAL OF INSECT PHYSIOLOGY 2006; 52:105-11. [PMID: 16271363 DOI: 10.1016/j.jinsphys.2005.09.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2005] [Revised: 09/26/2005] [Accepted: 09/26/2005] [Indexed: 05/05/2023]
Abstract
Only a few extracellular hematopoietic factors have been identified in insects. We previously developed an in vitro culture system for the larval hematopoietic organ (HPO) of the silkworm Bombyx mori, and found that cell proliferation is linked to hemocyte discharge from the HPO. In this study, we tested hematopoietic activity of bombyxin, a peptide in the insulin family. When silkworm HPO was cultured with synthetic bombyxin-II, the number of discharged hemocytes increased in a dose-dependent manner, indicating that bombyxin promoted cell proliferation in the HPO. However, a neutralization experiment using anti-bombyxin-II antibody revealed that bombyxin is not the primary effector in larval plasma. Similarly, bovine insulin showed hematopoietic activity. Addition of molting hormone, 20-hydroxyecdysone, circumstantially enhanced the hematopoietic activity of bombyxin and insulin. Bombyxin and insulin induced phosphorylation of different sets of proteins in the HPO, suggesting that their signaling pathways are different.
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Affiliation(s)
- Yuichi Nakahara
- National Institute of Agrobiological Sciences, 1-2 Ohwashi, Tsukuba, Ibaraki 305-8634, Japan
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Munyiri FN, Ishikawa Y. Endocrine changes associated with the starvation-induced premature metamorphosis in the yellow-spotted longicorn beetle, Psacothea hilaris. Gen Comp Endocrinol 2005; 144:150-5. [PMID: 16024020 DOI: 10.1016/j.ygcen.2005.05.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/25/2004] [Revised: 05/06/2005] [Accepted: 05/23/2005] [Indexed: 11/16/2022]
Abstract
Under 25 degrees C and a long day photoperiod, about half of the fourth instar Psacothea hilaris larvae molt to the fifth instar on day 13 and pupate about 18 days later; the rest pupate without a further larval molt with a mean fourth instar period of 24 days. However, starvation of fourth instar larvae exceeding a threshold weight induces premature pupation, resulting in the formation of small but morphologically normal adults. To clarify the endocrine basis for this premature pupation, hemolymph juvenile hormone (JH) and ecdysteroid titers were quantified during the fed and the starved periods. Normally fed fourth instar larvae exhibited two populations with regard to JH and ecdysteroid titers, one having JH titers ranging from 1.2 to 2.1 ng/ml through to day 13, the other, similarly high titers in the early part of the instar but low titers reaching 0.1 ng/ml on day 13. One population had ecdysteroid titers with a peak of 43 ng/ml on day 10, coinciding well with the period when some larvae normally molt to the fifth instar (day 13), the other, a small peak of 14 ng/ml on day 14 and a large peak of 70 ng/ml on day 17 coinciding well with the period just before the prepupa stage. When fourth instar larvae were starved after 4 days of feeding, JH titers decreased sharply in the next 24h and never recovered, and a small but significant increase (to 21 ng/ml) in ecdysteroid titers was observed on day 6, followed by a large peak of 63 ng/ml on day 11. Altogether, these results suggest that starvation induces a rapid decline in the JH titer, and this cues the early occurrence of a small ecdysteroid peak that commits larvae to early metamorphosis.
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Affiliation(s)
- Florence N Munyiri
- Laboratory of Applied Entomology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan
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Koyama T, Obara Y, Iwami M, Sakurai S. Commencement of pupal commitment in late penultimate instar and its hormonal control in wing imaginal discs of the silkworm, Bombyx mori. JOURNAL OF INSECT PHYSIOLOGY 2004; 50:123-133. [PMID: 15019513 DOI: 10.1016/j.jinsphys.2003.09.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2003] [Revised: 09/25/2003] [Accepted: 09/26/2003] [Indexed: 05/24/2023]
Abstract
Pupal commitment of the wing imaginal disc of the silkworm, Bombyx mori, is completed shortly after the final (fifth) larval ecdysis. Pupal commitment was induced by in vitro culture with 20-hydroxyecdysone (20E). Shortly after the head capsule slippage (HCS) that occurs approximately 24 h before the final larval ecdysis, the discs become competent to respond to 20E, indicating that the process of pupal commitment begins in the late penultimate (fourth) instar. The simultaneous presence of methoprene (JHA) with 20E suppressed the pupal commitment at 4 ng/ml for the discs at 12 h after HCS and at 240 ng/ml for the discs at the ecdysis. Thus, the discs rapidly lose their sensitivity to JH at the end of the fourth instar. Day 0 fourth wing discs were not pupally committed by 20E when freshly dissected discs were exposed to 20E. By contrast, exposure to 20E after a pre-culture in a hormone free medium induced the pupal commitment. In those discs, the effective JHA concentration to suppress the 20E effects was 0.1 ng/ml. The present data suggest that pupal commitment proceeds through two stages from a reversible state that begins at around HCS to an irreversible state early in the fifth instar. The loss of sensitivity to JH is the primary impetus to begin the process and 20E is the factor that drives the discs to enter the reversible state.
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Affiliation(s)
- Takashi Koyama
- Division of Life Sciences, Graduate School of Science and Technology, Kanazawa University, Kakumamachi, Kanazawa 920-1192, Japan
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Takahashi M, Kikuchi K, Tomita S, Imanishi S, Nakahara Y, Kiuchi M, Kamimura M. Transient in vivo reporter gene assay for ecdysteroid action in the Bombyx mori silk gland. Comp Biochem Physiol B Biochem Mol Biol 2003; 135:431-7. [PMID: 12831763 DOI: 10.1016/s1096-4959(03)00094-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
To analyze the molecular mechanisms underlying hormone-regulated gene expression during molt and metamorphosis, we developed a transient reporter gene assay system using the silkworm anterior silk gland. Reporter plasmids were delivered into dissected anterior silk glands by particle bombardment and bombarded glands transplanted into other larvae, to which hormones were then administered. When the green fluorescent protein gene, coupled with the constitutive cytoplasmic actin gene A3 promoter, was introduced into the anterior silk gland, strong green fluorescence was observed a few days later. Bombarded silk glands transplanted into other larvae showed the same morphological changes as intrinsic glands after 20-hydroxyecdysone (20E) alone or 20E plus juvenile hormone (JH) treatment, indicating that the transplanted gland received hormonal signals properly. When a 20E-responsive reporter construct containing four tandemly repeated pal-1 ecdysone response elements upstream from the luciferase gene was delivered into the gland, an approximately 50-fold increase in luciferase activity was detected 30 h after 20E injection. This induction was comparable to that in an ecdysteroid-responsive Bombyx cell line. This in vivo reporter assay system is thus a rapid, effective tool for analyzing gene expression regulated by 20E and probably by JH.
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Affiliation(s)
- Michiyoshi Takahashi
- Developmental Biology Department, National Institute of Agrobiological Sciences, 1-2, Owashi, Tsukuba, Ibaraki 305-8634, Japan
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Kiuchi M, Yasui H, Hayasaka S, Kamimura M. Entomogenous fungus Nomuraea rileyi inhibits host insect molting by C22-oxidizing inactivation of hemolymph ecdysteroids. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2003; 52:35-44. [PMID: 12489132 DOI: 10.1002/arch.10060] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The entomogenous fungus Nomuraea rileyi reportedly secretes a proteinaceous substance inhibiting larval molt and metamorphosis in the silkworm Bombyx mori. We studied the possibility that N. rileyi controls B. mori development by inactivating hemolymph molting hormone, ecdysteroids. Incubation of ecdysone (E) and 20-hydroxyecdysone (20E) in fungal-conditioned medium resulted in their rapid modification into products with longer retention times in reverse-phase HPLC. Each modified product from E and 20E was purified by HPLC, and identified by NMR as 22-dehydroecdysone and 22-dehydro-20-hydroxyecdysone. Some other ecdysteroids with a hydroxyl group at position C22 were also modified. Injection of the fungal-conditioned medium into Bombyx mori larvae in the mid-4th instar inhibited larval molt but induced precocious pupal metamorphosis, and its injection into 5th instar larvae just after gut purge blocked pupal metamorphosis. In hemolymph of injected larvae, E and 20E disappeared and, in turn, 22-dehydroecdysone and 22-dehydro-20-hydroxyecdysone accumulated. These results indicate that N. rileyi secretes a specific enzyme that oxidizes the hydroxyl group at position C22 of hemolymph ecdysteroids and prevents molting in B. mori larvae.
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Affiliation(s)
- Makoto Kiuchi
- National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan
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