Abstract

Vitellogenesis is pre-requisite to insect egg production and embryonic development after oviposition. During insect vitellogenesis, the yolk protein precursor vitellogenin (Vg) is mainly synthesized in the fat body, transported by the hemolymph through the intercellular spaces (known as patency) in the follicular epithelium to reach the membrane of maturing oocytes, and sequestered into the maturing oocytes via receptor-mediated endocytosis. Insect vitellogenesis is governed by two critical hormones, the sesquiterpenoid juvenile hormone (JH) and the ecdysteriod 20-hydroxyecdysone (20E). JH acts as the principal gonadotropic hormone to stimulate vitellogenesis in basal hemimetabolous and most holometabolous insects. 20E is critical for vitellogenesis in some hymenopterans, lepidopterans and dipterans. Furthermore, microRNA (miRNA) and nutritional (amino acid/Target of Rapamycin and insulin) pathways interplay with JH and 20E signaling cascades to control insect vitellogenesis. Revealing the regulatory mechanisms underlying insect vitellogenesis is critical for understanding insect reproduction and helpful for developing new strategies of insect pest control. Here, we outline the recent research progress in the molecular action of gonadotropic JH and 20E along with the role of miRNA and nutritional sensor in regulating insect vitellogenesis. We highlight the advancements in the regulatory mechanisms of insect vitellogenesis by the coordination of hormone, miRNA and nutritional signaling pathways.

Highlights

  • A hallmark of female insect reproduction is vitellogenesis, a heterosynthetic process by which vitellogenin (Vg) is mostly synthesized in the fat body and deposited into developing oocytes

  • juvenile hormone (JH) acts via Met to induce the expression of Regulator of Ribosome Synthesis 1 (RRS1) and Ribosomal protein L32 (RpL32), enhancing ribosomal biogenesis in the fat body essential for massive Vg synthesis

  • Accumulative studies have advanced our understanding of how insect vitellogenesis is governed by hormonal and nutritional pathways. 20E acts through its receptor complex comprised of Ecdysone Receptor (EcR) and Ultraspiracle (USP), leading to transcriptional activation of 20E-response genes including ecdysone-induced proteins 74 (E74), 75 (E75), 93F (E93), Broad-Complex (BrC), and Ftz-f1

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Summary

Introduction

A hallmark of female insect reproduction is vitellogenesis, a heterosynthetic process by which vitellogenin (Vg) is mostly synthesized in the fat body and deposited into developing oocytes. In adult females of L. migratoria, JH induces Vg synthesis in the fat body, initiates intercellular space (patency) in the follicular epithelium, and facilitates the uptake of Vg into developing oocytes (Wyatt and Davey, 1996; Song and Zhou, 2020).

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