Progress 10/01/16 to 09/30/17
Outputs
Target Audience:Professional researchers, faculty, undergraduate and graduate students, post-doctoral scholars Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?Research supported by NIH and HATCH funds has provided to train researchers in my area of expertize. They were 2 undergraduate and 2 graduate students, 4 postdocs and 4 postgraduate visiting scholars How have the results been disseminated to communities of interest?Publications of articles and reviews in scientific journals, seminar presentaations, paritipation in research conferences and meetings. What do you plan to do during the next reporting period to accomplish the goals?Thenext year goal for this project is to continue investigation ofthe mode of action of the Arthropod-specific hormone - juvenile hormone. Recently, we have identified that many processes in female mosquitoes require interaction of several regulatory hormones, including JH, ecdysone and insulins (insulin-like peptides). We will investigate the molecular mechanism underlying this complex regulation in mosquito reproduction and metabolism.
Impacts
What was accomplished under these goals?
Introduction: Arthropod-specific juvenile hormones control numerous essential functions in development and reproduction. In the dengue-fever mosquito Aedes aegypti, in addition to its role in immature stages, juvenile hormone III (JH) governs post-eclosion (PE) development in adult females, a phase required for competence acquisition for blood feeding and subsequent egg maturation. In the Aedes aegypti mosquito, a vector of Dengue, Yellow fever, Chikungunya and Zika viruses, the metabolic tissue--the fat body--produces yolk proteins (YPs) for developing oocytes. JH is important for the fat body to acquire competence for YP production. However, the molecular mechanisms of how JH promotes mosquito reproduction are not completely understood. In this reported period we have accomplished significant progress in two specific aims of the project: We will establish factors that are required for activation and repression of gene expression by juvenile hormone (JH). We will conduct RNA interference (RNAi) experiments to evaluate the JHrepressive hierarchy. Juvenile hormone and its receptor Methoprene-tolerant promote ribosomal biogenesis and vitellogenesis in the Aedes aegypti mosquito. Wang, J. et al. 2017. J. Biol. Chem., 292(24):10306-10315. What has been studied: In this work, we investigated how JH activates gene expression in the female mosquitoes. Technical report: The JH receptor Met activates expression of genes encoding the regulator of ribosome synthesis 1 (RRS1) and six ribosomal proteins. Met directly binds to the RRS1 gene promoter. Moreover, RNAi-mediated depletion of RRS1 decreased biosynthesis of the ribosomal protein L32 (RpL32). Depletion of Met, RRS1, or RpL32 led to retardation of ovarian growth and reduced mosquito fecundity, which may at least in part have resulted from decreased Vg protein production in the fat body. In summary, our results indicate that JH is critical for inducing the expression of ribosomal protein genes and demonstrate that RRS1 mediates the JH signal to enhance both ribosomal biogenesis and vitellogenesis. Major conclusion: We show that JH act through its receptor Methoprene-tolerant (Met). In turn, Met binds to gene regulatory regions activating their expression. Hormone and receptor interplay in the regulation of mosquito lipid metabolism. Wang, X.L. et al. 2017. Proc. Natl. Acad. Sci. USA 114(13):E2709-E2718. What has been studied: Mosquitoes transmit devastating human diseases because they need vertebrate blood for the egg development. Metabolism in female mosquitoes is tightly coupled with blood-meal mediated reproduction, which requires an extremely high level of energy consumption. We investigated the role of JH and Met in regulation of lipid metabolism. Technical report: Transcriptomic analysis has shown that major genes encoding for enzymes involved in lipid metabolism (LM) in the mosquito fat bodies are downregulated at the end of the juvenile hormone (JH)-controlled post-eclosion (PE) phase before female takes a blood meal. Reduction in the transcript levels of genes encoding triacylglycerol (TAG) catabolism and β-oxidation enzymes was observed to correlate with a dramatic accumulation of lipids in the PE phase. The RNA-interference (RNAi) depletion of Met reversed the LM gene expression and the levels of lipid stores and metabolites, demonstrating the critical roles of this JH receptor in LM regulation. Major conclusion: This study has proved a link between hormonal regulation and LM in female mosquitoes. Synergistic Action of the Transcription Factors Krüppel Homolog 1 and Hairy in Juvenile Hormone/Methoprene-Tolerant-Mediated Gene Repression in the mosquito Aedes aegypti (manuscript in preparation). What has been studied: The major question of this investigation is how JH represses gene expression. What are the factors involved in this process? Technical report: Our transcriptomic analysis has shown that JH and its receptor Met regulate the expression of a large number of genes, causing either activation or repression. We have demonstrated that Met-mediated gene repression is indirect, requiring involvement of intermediate repressors. Hairy, which functions downstream of Met in the JH gene-repression hierarchy, is one such factor. Krüppel homolog 1 (Kr-h1), a zinc-finger transcriptional factor, is directly regulated by Met and has been implicated in both activation and repression of JH-regulated genes. Our RNAseq-based transcriptomic analysis of the Kr-h1-depleted mosquito fat body revealed that Kr-h1 repressed genes are also repressed by Met, strongly suggesting a hierarchy between Met and Kr-h1. Notably, 130 genes are co-repressed by both Kr-h1 and Hairy, indicating regulatory complexity of the JH-mediated PE gene repression. A mosquito Kr-h1 binding site in genes co-regulated by this factor and Hairy was determined computationally and confirmed by biochemical approaches. Major conclusion: Our results indicate that JH and Met gene repression occurs through two factors, Hairy and Kr-h1. Not only they function as intermediate downstream factors, but also act together in a synergistic fashion in the JH/Met gene-repression.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2017
Citation:
Ling, L., Kokoza, V.A., Zhang, C., Aksoy, E., Raikhel, A.S. 2017. MicroRNA-277 targets insulin-like peptides 7 and 8 to control lipid metabolism and reproduction in Aedes aegypti mosquitoes. Proc Natl Acad Sci U S A., 114(38):E8017-E8024.
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Progress 12/11/15 to 09/30/16
Outputs
Target Audience:Accomplished research targets researchers, postdoctoral fellows and graduate and undergraduate students studying insect endocrinology, metabolism and reproduction Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?This project has provided opportunities for training and professional development of three graduate students and four postdoctoral researchers. In addition, four visiting scholars have been trained in my laboratory. How have the results been disseminated to communities of interest?Journal publications and review articles: Hou, Y., Wang, X-L., Saha, T.T., Roy, S., Zhao, B., Raikhel, A.S. and Zou, Z. 2015. Temporal coordination of carbohydrate metabolism during mosquito reproduction. Plos Genetics 11(7):e1005309. Saha, T.T., Shin, S.W., Dou, W., Zhao, B., Roy, S., Hou, Y., Wang, X-L., Zou, Z., Girke, T., and Raikhel, A.S. 2016. Hairy and Groucho mediate the juvenile hormone receptor Methoprene-tolerant action in gene repression. Proc. Natl. Acad. Sci. USA 113(6):E35-43. Wang, J., Saha, T.T., Zhang, Y., Zhang, C., Raikhel, A.S. 2017a. Juvenile hormone and its receptor Methoprene-tolerant promote ribosomal biogenesis and vitellogenesis in the Aedes aegypti mosquito. J. Biol. Chem., 292(24):10306-10315.. Wang, X.L., Hou, Y., Saha, T.T., Pei, G.F., Raikhel, A.S., Zou, Z. 2017b. Hormone and receptor interplay in the regulation of mosquito lipid metabolism. Proc. Natl. Acad. Sci. USA 114(13):E2709-E2718. What do you plan to do during the next reporting period to accomplish the goals?During the next period we will continue characterizing the juvenile hormone regulatory pathway
Impacts
What was accomplished under these goals?
We established factors that are required for activation and repression of gene expression by juvenile hormone. We have generated a transgenic system in which juvenile hormone-activated early trypsin promoter serves as a biosensor for the juvenile hormone titer in the mosquito.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2016
Citation:
Saha, T.T., Shin, S.W., Dou, W., Zhao, B., Roy, S., Hou, Y., Wang, X-L., Zou, Z., Girke, T., and Raikhel, A.S. 2016. Hairy and Groucho mediate the juvenile hormone receptor Methoprene-tolerant action in gene repression. Proc. Natl. Acad. Sci. USA 113(6):E35-43.
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