Regulatory Pathways Controlling Female Insect Reproduction

Abstract

The synthesis of vitellogenin and its uptake by maturing oocytes during egg maturation are essential for successful female reproduction. These events are regulated by the juvenile hormones and ecdysteroids and by the nutritional signaling pathway regulated by neuropeptides. Juvenile hormones act as gonadotropins, regulating vitellogenesis in most insects, but ecdysteroids control this process in Diptera and some Hymenoptera and Lepidoptera. The complex crosstalk between the juvenile hormones, ecdysteroids, and nutritional signaling pathways differs distinctly depending on the reproductive strategies adopted by various insects. Molecular studies within the past decade have revealed much about the relationships among, and the role of, these pathways with respect to regulation of insect reproduction. Here, we review the role of juvenile hormones, ecdysteroids, and nutritional signaling, along with that of microRNAs, in regulating female insect reproduction at the molecular level.

RNA interference‐mediated knockdown of the transcription factor Krüppel homologue 1 suppresses vitellogenesis in Chilo suppressalis

“…Vitellogenesis is a central event of female reproduction and is controlled by hormones: ILPs, JH and 20E (Roy et al, ). Our RNAi experiment indicates that silencing of Kr‐h1 dramatically decreases Vg expression, oocyte maturation and ovarian growth, suggesting that Kr‐h1 is involved in insect vitellogenesis and the development of the ovary.…”

“…Additionally, 20E also influences Vg synthesis through its effects on oocyte maturation (Parthasarathy et al, ). 20E acts through its cognate receptors EcR and USP ; more specifically, the 20E‐bound EcR‐USP heterodimer interacts with the ecdysone response element (EcRE) thereby activating the expression of early genes, including E74 and BRC (Koelle et al, ; Thomas et al, ; Yao et al, ; Goodman and Cusson, ; Roy et al, ). The Vg 5′ regulatory region contains several EcREs that bind directly to EcR‐USP , controlling Vg transcription (Raikhel et al, ).…”

“…Kr-h1 also participates in many aspects of insect physiology including development and reproduction (Miyakawa et al, 2018;Yue et al, 2018) and has been closely associated with oogenesis (Roy et al, 2018). Recent studies revealed that ovarian development in Nilaparvata lugens is under the control of both BR-C and Kr-h1, which jointly determined of the number of ovarioles (Jiang et al, 2017).…”

Juvenile hormone signaling – a mini review

“…In A . aegypti , JH signaling controls a critical previtellogenic preparatory phase in fat body cells (Roy et al ., ). Besides Kr‐h1, the JH‐Met complex directly activates genes such as hairy the products of which are transcriptional repressors acting on JH‐inhibited genes (Saha et al ., ).…”

Juvenile hormone–dependent Kazal‐type serine protease inhibitor Greglin safeguards insect vitellogenesis and egg production

“…In more advanced dipteran insects, such as the fruit fly Drosophila melanogaster, JH is required for Vg uptake into oocytes (27,28). In the mosquito Aedes aegypti, JH controls the previtellogenic development of the fat body that is competent for Vg synthesis after a blood meal (4,22). Although extensive studies have been conducted to elucidate the mechanisms of JH suppression on 20E-initated metamorphosis, the molecular basis of JH in stimulating insect reproduction is less well understood.…”