Comprehensive Molecular Insect Science
3.9 - Hormonal Control of Reproductive Processes
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Cited by (269)
The neuroendocrine and endocrine systems in insect – Historical perspective and overview
2024, Molecular and Cellular EndocrinologyA complex cascade of events leads to the initiation and maintenance of a behavioral act in response to both internally and externally derived stimuli. These events are part of a transition of the animal into a new behavioral state, coordinated by chemicals that bias tissues and organs towards a new functional state of the animal. This form of integration is defined by the neuroendocrine (or neurosecretory) system and the endocrine system that release neurohormones or hormones, respectively. Here we describe the classical neuroendocrine and endocrine systems in insects to provide an historic perspective and overview of how neurohormones and hormones support plasticity in behavioral expression. Additionally, we describe peripheral tissues such as the midgut, epitracheal glands, and ovaries, which, whilst not necessarily being endocrine glands in the pure sense of the term, do produce and release hormones, thereby providing even more flexibility for inter-organ communication and regulation.
Conserved role of juvenile hormone in regulating behavioural maturation and division of labour in a highly eusocial wasp
2023, Animal BehaviourJuvenile hormone (JH) in insects plays a key role in regulating reproduction, but in some social insects it has also acquired secondary functions in regulating the age-related division of labour among the workers. Previous work has shown that JH regulates division of labour in honey bees, in several primitively eusocial paper wasps and in leafcutter ants, which comprise three independent origins of sociality. It remains unclear, however, to what degree JH could have a conserved role in regulating division of labour within these clades. To this end, we investigated whether JH also regulates division of labour in the highly eusocial Vespine wasp Vespula vulgaris, in which JH had previously been shown only to regulate reproduction and affect queen pheromone signalling. In line with JH having a conserved role in regulating division of labour in social wasps, we show that JH in this species indeed affected behavioural maturation and division of labour in the worker caste. In particular, topical application of the JH analogue methoprene onto workers accelerated behavioural maturation and hastened the onset of foraging, thereby significantly decreasing the time they spent conducting activities inside the nest. We discuss how this conserved role of JH in regulating division of labour could indicate the same conserved genetic toolkits being used to regulate division of labour across several independent origins of sociality. In addition, we examine the implications of JH having several pleiotropic effects in this species and discuss whether this could constrain the expression of reproductive conflicts in their societies.
Halloween genes AhCYP307A2 and AhCYP314A1 modulate last instar larva–pupa–adult transition, ovarian development and oogenesis in Agasicles hygrophila (Coleoptera: Chrysomelidae)
2023, Journal of Integrative AgricultureIn insects, ecdysteroids are synthesized by genes of the Halloween family and play important roles in several key developmental events, including molting and metamorphosis. However, the roles of these genes in Agasicles hygrophila are still largely unknown. In this study, the expression patterns of the two Halloween genes AhCYP307A2 and AhCYP314A1 were determined by quantitative PCR (qPCR) at different developmental stages. Moreover, the functions of these two genes were explored using RNA interference (RNAi), and ovarian development was observed by dissecting the ovaries of A. hygrophila females. The qPCR results showed that AhCYP307A2 and AhCYP314A1 were highly expressed in last instar larvae and in adult females. In addition, AhCYP307A2 was also highly expressed in eggs and pupae but was markedly lower than in third-instar larvae and females. The RNAi results showed that the injection of dsAhCYP307A2 or dsAhCYP314A1 markedly inhibited their expression and the transcription levels of three related AhVgs. Knockdown of AhCYP307A2 or AhCYP314A1 significantly inhibited larval molting, impaired last instar larva–pupa–adult transition, delayed ovarian development, and stopped egg production (i.e., no eggs were laid). These results indicate that AhCYP307A2 and AhCYP314A1 play important regulatory roles in last instar larva–pupa–adult transition and reproduction in A. hygrophila.
Diallyl trisulfide reduced the reproductive capacity of male Sitotroga cerealella via the regulation of juvenile and ecdysone hormones
2022, Ecotoxicology and Environmental SafetyEnvironmental pollution and resistance in animals are major concerns for the application of synthetic pesticides. Diallyl trisulfide (DAT), an active compound in garlic essential oil, is a novel tool for active and safe control of agricultural insect pests. In this study, we analysed the effects of DAT (0.01 μL/L) on the protein content in male reproductive tissues (accessory glands, ejaculatory ducts, and testis), and juvenile hormone (JH) and ecdysone titres in a highly detrimental pest of stored products, Sitotroga cerealella. Evaluation of the expression profile of JH and ecdysone pathway-related genes in various tissues indicated that the accessory gland protein and ecdysone titres were markedly decreased after DAT fumigation, whereas the testis protein content and JH titre were increased. However, the protein content of the ejaculatory ducts remained unchanged between the treated and control groups. Further investigation revealed that DAT disrupted the mRNA expression of key enzymes involved in JH and ecdysone pathways. While increased mRNA levels of juvenile hormone acid O-methyltransferase (JHMAT) and Kruppel homologue 1 (Kr-h1) were observed after 4 and 7 h of DAT fumigation, the levels of juvenile hormone epoxide hydrolase (JHEH) were substantially reduced 3 h post-fumigation. mRNA levels of the ecdysone-responsive gene, FTZF1, and cytochrome P450 enzyme, CYP315A1, were notably decreased at 7 h and 4 h, respectively, post-fumigation, whereas CYP314A1 and CYP302A1 mRNA levels decreased after 3 h and 4 h, respectively. While DAT fumigation disrupted sperm number in the testis, ejaculatory ducts, and seminal vesicles, topical application of the 20-hydroxyecdysone (20E) analogue also lowered sperm number in the ejaculatory ducts. Topical application of methoprene, a JH analogue, increased the protein content in the testes, but not in the accessory glands or ejaculatory ducts. However, the survival rate was not affected by the topical application of methoprene or 20E. These data suggest that DAT regulates JH and ecdysone via its molecular pathway genes and modulates endocrine secretion during the male reproductive process.
Anti-proliferative and apoptosis-inducing effects of juvenile hormone analogue, fenoxycarb in the Sf21cell line
2022, Pesticide Biochemistry and PhysiologyThe apprehension regarding the possible environmental effects of synthetic pesticides has led to the discovery and production of environmental friendly pesticides. Insect hormone mimics, mainly juvenile hormone analogues, like fenoxycarb have acquired attention due to their greater specificity than conventional broad-range insecticides as pest control agents. The study explored the effects of the insecticide juvenile hormone analogue (JHA), fenoxycarb, on the Sf21 cell line of Spodoptera frugiperda to illustrate the mode of action. Cytotoxicity assay was conducted at different concentrations of fenoxycarb ranging from 0.5 nM to 10 μM. The results showed the concentration-and time-dependent anti-proliferative effect of fenoxycarb. The median inhibitory concentration (IC50) was calculated as 28 nM at 48 h of exposure, and IC50 and IC25 concentrations were used for further cytotoxicity screening assays. Furthermore, the significant morphological changes of the cells after 48 h revealed the development of apoptotic bodies, membrane blebbing, cell size reduction, and irregular cell aggregation; additionally, enlarged cell spaces and widely diffused apoptotic bodies were observed after 72 h of insecticide exposure. In the confocal microscopic analysis of fenoxycarb treated cells, the nucleus was observed to condense and collapse into many fragments by Hoechst-33,342. Assessment of the relative potential of the cell cycle at two concentrations (IC50& IC25) reported the concentration-and time-dependent reduction of cells in the G1 phase with an upsurge in apoptotic cells. The percentage of cells that underwent apoptotic changes, such as loss of mitochondrial membrane potential (MMP), was strictly dependent on the fenoxycarb concentration and duration of exposure. The findings confirm the presence of fenoxycarb-mediated cell proliferation inhibition and apoptosis in Sf21 cell lines.
Knockdown of ecdysone receptor in male desert locusts affects relative weight of accessory glands and mating behavior
2022, Journal of Insect PhysiologyLocusts have been known as pests of agricultural crops for thousands of years. Recently (2018–2021) the world has faced the largest swarms of desert locusts, Schistocerca gregaria, in decades and food security in large parts of Africa and Asia was under extreme pressure. There is an urgent need for the development of highly specific bio-rational pesticides to combat these pests. However, to do so, fundamental research is needed to better understand the molecular mechanisms behind key physiological processes underpinning swarm formation, such as development and reproduction. The scope of this study is to investigate the possible role(s) of the ecdysteroid receptor in the reproductive physiology of male S. gregaria. Ecdysteroids and juvenile hormones are two important classes of insect hormones and are key regulators of post-embryonic development. Ecdysteroids are best known for their role in moulting and exert their function via a heterodimer consisting of the nuclear receptors ecdysone receptor (EcR) and retinoid-X receptor (RXR). To gain insight into the role of SgEcR and/or SgRXR in the male reproductive physiology of S. gregaria we performed RNAi-induced knockdown experiments. A knockdown of SgEcR, but not SgRXR, resulted in an increased relative weight of the male accessory glands (MAG). Furthermore, the knockdown of these genes, either in combination or separately, caused a significant delay in the onset of mating behavior. Nevertheless, the MAG appeared to mature normally and the fertility of mated males was not affected. The high transcript levels of SgEcR in the fat body, especially towards the end of sexual maturation in both males and females, represent a remarkable finding since as of yet the exact role of SgEcR in this tissue in S. gregaria is unknown. Finally, our data suggest that in some cases SgEcR and SgRXR might act independently of each other. This is supported by the fact that the spatiotemporal expression profiles of SgEcR and SgRXR do not always coincide and that knockdown of SgEcR, but not SgRXR, significantly affected the relative weight of the MAG.