Effect of Insulin Receptor on Juvenile Hormone Signal and Fecundity in Spodoptera litura (F.)

Abstract

Insulin signaling can regulate various physiological functions, such as energy metabolism and reproduction and so on, in many insects, including mosquito and locust. However, the molecular mechanism of this physiological process remains elusive. The tobacco cutworm, Spodoptera litura, is one of the most important pests of agricultural crops around the world. In this study, phosphoinositide 3-kinase (SlPI3K), protein kinase B (SlAKT), target of rapamycin (SlTOR), ribosomal protein S6 kinase (SlS6K) and transcription factor cAMP-response element binding protein (SlCREB) genes, except transcription factor forkhead box class O (SlFoxO), can be activated by bovine insulin injection. Then, we studied the influence of the insulin receptor gene (SlInR) on the reproduction of S. litura using RNA interference technology. qRT-PCR analysis revealed that SlInR was most abundant in the head. The SlPI3K, SlAKT, SlTOR, SlS6K and SlCREB genes were decreased, except SlFoxO, after the SlInR gene knockdown. Further studies revealed that the expression of vitellogenin mRNA and protein, Methoprene-tolerant gene (SlMet), could be down-regulated by the injection of dsRNA of SlInR significantly. Furthermore, a depletion in the insulin receptor by RNAi significantly decreased the content of juvenile hormone III (JH-III), total proteins and triacylgycerol. These changes indicated that a lack of SlInR could impair ovarian development and decrease fecundity in S. litura. Our studies contribute to a comprehensive insight into reproduction, regulated by insulin and the juvenile hormone signaling pathway through nutrition, and a provide theoretical basis for the reproduction process in pest insects.

Quantitative transcriptomic and proteomic analyses reveal the potential maintenance mechanism of female adult reproductive diapause in Chrysoperla nipponensis

“…27 RNAi knockdown of IR delayed ovarian development and resulted in a lower JH titer. 53 Similarly, mutation of IR reduced JH synthesis in D. melanogaster. 54 These findings suggested that the insulin pathway is involved in the insect diapause process by altering the JH synthesis.…”

“…Application of the JH analog methoprene rescued ovarian development in dsInR ‐injected Culex pipiens 27 . RNAi knockdown of IR delayed ovarian development and resulted in a lower JH titer 53 . Similarly, mutation of IR reduced JH synthesis in D. melanogaster 54 .…”

The diverse roles of insulin signaling in insect behavior

“…With PI3K/Akt, IRS binds to PI3K, activating Akt, which phosphorylates and inhibits a class O of forkhead box transcription factor (FOXO) and its downstream targets ( 27 , 28 ), including developmental growth and differentiation regulators in conserved pathways such as hedgehog signaling ( 29 – 31 , see 32 for an example of FOXO activity in adults). Akt can also activate the cAMP-response element binding protein (CREB, involved in memory formation) and inactivate glycogen synthase kinase 3 (GSK3), promoting glycogen synthesis and energy storage ( 23 , 33 – 35 ). Alternatively, IRS can interact with growth factor receptor bound protein-2 (Grb2), ultimately initiating MAPK signaling ( 23 ).…”

Role of nuclear protein Akirin in the modulation of female reproduction in Nilaparvata lugens (Hemiptera: Delphacidae)

“…The synthesis of insect Vg, maturation of oocytes, and uptake of Vg by mature oocytes play pivotal roles in the reproductive development of female insects, which are regulated by crucial hormones [juvenile hormone (JH) and ecdysone (Ecd) ( Roy et al, 2018 ; Santos et al, 2019 )] and multiple signaling pathways. As nutrient sensors, the amino acid/Target of Rapamycin signaling pathway (AA/TOR) and insulin pathway (or insulin-like peptide signaling pathway, ILP) participate in JH and Ecd biosynthesis, interacting synergistically with JH and Ecd to regulate insect yolk formation ( Zhu et al, 2020 ; Dong et al, 2021 ; Pan et al, 2022 ).…”