A male steroid controls female sexual behaviour in the malaria mosquito

Abstract

Insects, unlike vertebrates, are widely believed to lack male-biased sex steroid hormones1. In the malaria mosquito Anopheles gambiae, the ecdysteroid 20-hydroxyecdysone (20E) appears to have evolved to both control egg development when synthesized by females2 and to induce mating refractoriness when sexually transferred by males3. Because egg development and mating are essential reproductive traits, understanding how Anopheles females integrate these hormonal signals can spur the design of new malaria control programs. Here we reveal that these reproductive functions are regulated by distinct sex steroids through a sophisticated network of ecdysteroid-activating/inactivating enzymes. We identify a male-specific oxidized ecdysteroid, 3-dehydro-20E (3D20E), which safeguards paternity by turning off female sexual receptivity following its sexual transfer and activation by dephosphorylation. Notably, 3D20E transfer also induces expression of a reproductive gene that preserves egg development during Plasmodium infection, ensuring fitness of infected females. Female-derived 20E does not trigger sexual refractoriness but instead licenses oviposition in mated individuals once a 20E-inhibiting kinase is repressed. Identifying this male-specific insect steroid hormone and its roles in regulating female sexual receptivity, fertility and interactions with Plasmodium parasites suggests the possibility for reducing the reproductive success of malaria-transmitting mosquitoes.

Genetic characterisation of candidate ecdysteroid kinases inDrosophila melanogaster

“…The UAS- CG5644 line was further crossed to the phm-GAL4 driver at 25 °C, resulting in 66 misexpression adults surviving compared to 115 balancer adults (proportion = 0.365, 95% CI: 0.295– 0.439, p = 0.0003, binomial test), suggesting PG misexpression of CG5644 can also disrupt development. These data are consistent with the hypothesis that CG5644 encodes an ecdysteroid 22-kinase, previously proposed based on 1:1 orthology to AgEcK2 in Anopheles gambiae (Peng et al 2022; Scanlan & Robin 2023). The lack of developmental arrest seen in tub>CG31300 and tub>JhI-26 individuals is consistent with previously published experimental data (Liu et al 2014; Scanlan et al 2022).…”

“…Plausible, alternative ecdysteroid substrates for Wall are 3-dehydroecdysteroids and 3-epiecdysteroids, which are produced in the fat body and epidermis of larvae (Sommé-Martin et al 1988a, 1988b and may have signalling functions in D. melanogaster (Sommé-Martin et al 1990;Baker et al 2003). The physiological functions of these modified ecdysteroids are still unclear in D. melanogaster, but intriguingly, 3-dehydro-20E was recently found to modulate female reproductive physiology in the mosquito Anopheles gambiae (Peng et al 2022). Additionally, Cavigliasso et al (2023) recently suggested fezzik (fiz) encodes an ecdysteroid oxidase that adaptively modulates larval growth rate under malnutrition in D. melanogaster (Grenier et al 2023;Glaser-Schmitt & Parsch 2018).…”

“…In the mosquito Anopheles gambiae (Diptera: Culicidae), 3-dehydro-20E 22-phosphate is a male sexual gift that is dephosphorylated in the female reproductive tract to prevent remating (Peng et al 2022). 20E is also converted to a 22-phosphate in virgin females of this species to modulate the hormonal response to blood-feeding (Peng et al 2022). In Musca domestica (Diptera: Muscidae), ecdysteroid 2-phosphorylation can be induced by a synthetic ecdysteroid agonist but its physiological function remains unclear (Williams et al 2002).…”

“…Ecdysteroid inactivation can modulate ecdysteroid signalling by reducing levels of active hormone and/or producing inactive “storage” forms that can be recycled into active hormones. This can play important roles in reproduction, where maternal- or mate-contributed storage hormones can influence early development or reproductive physiology, respectively (Sonobe & Ito 2009; Peng et al 2022; Crocker & Hunter 2018). It can also function in development, by shaping the pulse-like titres of 20E required for developmental transitions (Rewitz et al 2010).…”

Functional transcriptome analyses of Drosophila suzukii midgut reveal mating-dependent reproductive plasticity in females

“…During mating, males transfer seminal fluid proteins that trigger the switch between virgin and mated female states. The transition involves a series of molecular, morphological, behavioral and physiological changes, and occurs in rapid and sustained phases [27][28][29][30][31]. Short-term post-mating responses occur during the first 24 h, while long-term post-mating responses can last up to two weeks after mating [27][28][29][30]32].…”