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      Identification and characterization of genes involving the early step of Juvenile Hormone pathway in Helicoverpa armigera

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          Abstract

          Juvenile hormones (JHs) are crucial regulators for multiple physiological processes in insects. In the current study, 10 genes in mevalonate pathway involved in JH biosynthesis were identified from Helicoverpa armigera. Tissue-specific expression analysis showed that six genes were highly expressed in the head which contained the JH biosynthetic gland (corpora allata). Temporal expression pattern showed that 10 of 12 genes were highly transcribed in the late 2 nd-instar when the in vivo JH titer reached the peak, indicating a tight correlation between JH titer and the transcription of JH synthetic pathway genes. Moreover, ingestion of methoprene, a JH analogue, significantly suppressed the transcription of nine JH biosynthetic genes and caused a feedback upregulation of the JH degradation enzyme. Particularly, the Acetoacetyl CoA thiolase ( HaAce) and Farnesyl diphosphate synthase gene 4 ( HaFpps4) showed high transcript abundance, and their temporal expressions keep pace with JH fluctuations. Further study by RNAi showed that knockdown of HaFpps4 caused the decrease of JH titer, led to a negative effect on the transcript levels of other genes in JH pathway, and resulted in molting disturbance in larvae. Altogether, these results contribute to our understanding of JH biosynthesis in H. armigera and provide target genes for pest control based on JH-dependent regulation.

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          Widespread adoption of Bt cotton and insecticide decrease promotes biocontrol services.

          Over the past 16 years, vast plantings of transgenic crops producing insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) have helped to control several major insect pests and reduce the need for insecticide sprays. Because broad-spectrum insecticides kill arthropod natural enemies that provide biological control of pests, the decrease in use of insecticide sprays associated with Bt crops could enhance biocontrol services. However, this hypothesis has not been tested in terms of long-term landscape-level impacts. On the basis of data from 1990 to 2010 at 36 sites in six provinces of northern China, we show here a marked increase in abundance of three types of generalist arthropod predators (ladybirds, lacewings and spiders) and a decreased abundance of aphid pests associated with widespread adoption of Bt cotton and reduced insecticide sprays in this crop. We also found evidence that the predators might provide additional biocontrol services spilling over from Bt cotton fields onto neighbouring crops (maize, peanut and soybean). Our work extends results from general studies evaluating ecological effects of Bt crops by demonstrating that such crops can promote biocontrol services in agricultural landscapes.
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            Insights into the molecular basis of the hormonal control of molting and metamorphosis from Manduca sexta and Drosophila melanogaster.

            This short review summarizes our current knowledge about the role of transcription factors regulated by ecdysteroids and juvenile hormone (JH) in larval molting and metamorphosis in the tobacco hornworm, Manduca sexta, and Drosophila melanogaster. We show new evidence that EcR-A/USP-2 and E75A contribute to the down-regulation of MHR3 after the peak of ecdysteroid. Also, there is suggestive evidence that both MHR4 and betaFTZ-F1 may regulate the expression of dopa decarboxylase as the ecdysteroid titer declines. We summarize the regulation by JH of the Broad transcription factor that normally appears in the epidermis in the final larval instar and specifies pupal cuticle formation at the metamorphic molt. Premature expression of different Broad isoforms also is shown to cause precocious degeneration of the prothoracic glands as well as to prevent ecdysteroid release during its presence.
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              A role for juvenile hormone in the prepupal development of Drosophila melanogaster.

              To elucidate the role of juvenile hormone (JH) in metamorphosis of Drosophila melanogaster, the corpora allata cells, which produce JH, were killed using the cell death gene grim. These allatectomized (CAX) larvae were smaller at pupariation and died at head eversion. They showed premature ecdysone receptor B1 (EcR-B1) in the photoreceptors and in the optic lobe, downregulation of proliferation in the optic lobe, and separation of R7 from R8 in the medulla during the prepupal period. All of these effects of allatectomy were reversed by feeding third instar larvae on a diet containing the JH mimic (JHM) pyriproxifen or by application of JH III or JHM at the onset of wandering. Eye and optic lobe development in the Methoprene-tolerant (Met)-null mutant mimicked that of CAX prepupae, but the mutant formed viable adults, which had marked abnormalities in the organization of their optic lobe neuropils. Feeding Met(27) larvae on the JHM diet did not rescue the premature EcR-B1 expression or the downregulation of proliferation but did partially rescue the premature separation of R7, suggesting that other pathways besides Met might be involved in mediating the response to JH. Selective expression of Met RNAi in the photoreceptors caused their premature expression of EcR-B1 and the separation of R7 and R8, but driving Met RNAi in lamina neurons led only to the precocious appearance of EcR-B1 in the lamina. Thus, the lack of JH and its receptor Met causes a heterochronic shift in the development of the visual system that is likely to result from some cells 'misinterpreting' the ecdysteroid peaks that drive metamorphosis.
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                Author and article information

                Contributors
                gmliang@ippcaas.cn
                Journal
                Sci Rep
                Sci Rep
                Scientific Reports
                Nature Publishing Group UK (London )
                2045-2322
                29 November 2017
                29 November 2017
                2017
                : 7
                : 16542
                Affiliations
                [1 ]ISNI 0000 0004 1808 3238, GRID grid.411859.0, Institute of Entomology, Jiangxi Agricultural University, ; Nanchang, 330045 China
                [2 ]ISNI 0000 0001 0526 1937, GRID grid.410727.7, State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, ; Beijing, 100193 China
                [3 ]GRID grid.411864.e, Jiangxi Key Laboratory of Bioprocess Engineering, Jiangxi Science & Technology Normal University, ; Nanchang, 330013 China
                [4 ]China Tobacco Midsouth Agricultural Experimental Station, Changsha, 410128 China
                Article
                16319
                10.1038/s41598-017-16319-z
                5707400
                29185447
                3d9fe995-2de0-43ee-acfb-5479dca41e6d
                © The Author(s) 2017

                Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

                History
                : 28 June 2017
                : 9 November 2017
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