Ecdysis-triggering hormone (ETH) was originally discovered and characterized as a molt termination signal in insects through its regulation of the ecdysis sequence. Here we report that ETH persists in adult Drosophila melanogaster, where it functions as an obligatory allatotropin to promote juvenile hormone (JH) production and reproduction. ETH signaling deficits lead to sharply reduced JH levels and consequent reductions of ovary size, egg production, and yolk deposition in mature oocytes. Expression of ETH and ETH receptor genes is in turn dependent on ecdysone (20E). Furthermore, 20E receptor knockdown specifically in Inka cells reduces fecundity. Our findings indicate that the canonical developmental roles of 20E, ETH, and JH during juvenile stages are repurposed to function as an endocrine network essential for reproductive success.ecdysis triggering hormone | ecdysone | juvenile hormone | fecundity | oogenesis T he life history of insects is characterized by radical morphogenetic transformations, whereby tissues are reorganized and hormones are repurposed for roles associated with stage-specific functions. During development, larvae complete each molt by shedding the cuticle under control of ecdysis triggering hormones (ETHs) targeting central peptidergic ensembles to orchestrate an innate behavioral sequence (1-3). Previous observations that Inka cells, the sole source of ETHs, persist into the adult stage (4) suggest possible reproductive functions for these peptides.We hypothesized that ETHs regulate juvenile hormone (JH) levels, based on the report of ETH receptor (ETHR) expression in the corpora allata (CA) of the silkworm, Bombyx mori (5). Evidence that ETH functions as an allatotropin in the yellow fever mosquito Aedes aegypti came from a recent study showing its activation of JH acid methyltransferase (6).JH is a sesquiterpenoid hormone with well-known morphogenetic and gonadotropic functions. In Drosophila, adult phenotypes resulting from reduction of JH levels have been characterized through induction of cell death in the CA or through enhancement of its degradation (7,8). Based on evidence from studies on Bombyx and Aedes, we investigated whether ETH functions as an allatotropin in adult Drosophila and the extent to which it may be necessary for reproductive functions.Previous studies showed that ecdysone (20E) regulates synthesis and release of ETH and expression of ETHR during larval stages of moths and mosquitoes (9-12). More recently, selftranscribing active regulatory region sequencing (STARR-Seq) data confirm that 20E induces 20E receptor (EcR) enhancer activity in promoters of both ETH and ETHR genes (13). Because circulating 20E levels are of major physiological and reproductive relevance (14), we also asked whether 20E influences ETH gene expression during the adult stage.Here we describe functional roles for 20E, ETH, and JH as a hormonal triad essential for reproductive success in Drosophila.In particular, we confirm persistence of ETH signaling throughout adulthood and demonstrate it...

Formation and expression of memories are critical for context-dependent decision making. In Drosophila, a courting male rejected by a mated female subsequently courts less avidly when paired with a virgin female, a behavioral modification attributed to "courtship memory." Here we show the critical role of hormonal state for maintenance of courtship memory. Ecdysis-triggering hormone (ETH) is essential for courtship memory through regulation of juvenile hormone (JH) levels in adult males. Reduction of JH levels via silencing of ETH signaling genes impairs short-term courtship memory, a phenotype rescuable by the JH analog methoprene. JH-deficit-induced memory impairment involves rapid decay rather than failure of memory acquisition. A critical period governs memory performance during the first 3 days of adulthood. Using sex-peptide-expressing "pseudo-mated" trainers, we find that robust courtship memory elicited in the absence of aversive chemical mating cues also is dependent on ETH-JH signaling. Finally, we find that JH acts through dopaminergic neurons and conclude that an ETH-JH-dopamine signaling cascade is required during a critical period for promotion of social-context-dependent memory.

In BriefProteomic analysis of Ampulex compressa venom reveals a multifaceted attack on the host central nervous system. Rather than inducing paralysis or cytotoxicity, the venom appears to modify endogenous signaling, rendering the host lethargic and compliant. Some peptides and proteins in the venom are in precursor form, only to be processed into fully active form once injected into the pH-neutral host brain. This analysis deepens mechanistic understanding of venom action and points to signaling systems previously unrecognized in regulation of locomotion. Graphical Abstract Highlights• The venom transcriptome and proteome (venome) of Ampulex compressa are reported.• 264 proteins (enzymes, peptides, neurotransmitters) were detected.• The venom contains unprocessed neuropeptide precursors absent mature peptides.• Neuropeptide precursors likely are processed into active form upon envenomation.The parasitoid emerald jewel wasp Ampulex compressa induces a compliant state of hypokinesia in its host, the American cockroach Periplaneta americana through direct envenomation of the central nervous system (CNS). To elucidate the biochemical strategy underlying venominduced hypokinesia, we subjected the venom apparatus and milked venom to RNAseq and proteomics analyses to construct a comprehensive "venome," consisting of 264 proteins. Abundant in the venome are enzymes endogenous to the host brain, including M13 family metalloproteases, phospholipases, adenosine deaminase, hyaluronidase, and neuropeptide precursors. The amphipathic, alpha-helical ampulexins are among the most abundant venom components. Also prominent are members of the Toll/NF-B signaling pathway, including proteases Persephone, Snake, Easter, and the Toll receptor ligand Spä tzle. We find evidence that venom components are processed following envenomation. The acidic (pHϳ4) venom contains unprocessed neuropeptide tachykinin and corazonin precursors and is conspicuously devoid of the corresponding processed, biologically active peptides. Neutralization of venom leads to appearance of mature tachykinin and corazonin, suggesting that the wasp employs precursors as a prolonged time-release strategy within the host brain post-envenomation. Injection of fully processed tachykinin into host cephalic ganglia elicits short-term hypokinesia. Ion channel modifiers and cytolytic toxins are absent in A. compressa venom, which appears to hijack control of the host brain by introducing a "storm" of its own neurochemicals. Our findings deepen understanding of the chemical warfare underlying host-parasitoid interactions and in particular neuromodulatory mechanisms that enable manipulation of host behavior to suit the nutritional needs of opportunistic parasitoid progeny.

Animals engage in motivated behaviors, such as feeding and mating behaviors, to ensure their own survival and the survival of their species. However, the neural circuits mediating the generation and persistence of these motivational drives remain poorly understood. Here we review recent studies on the circuit mechanisms underlying motivational states in Drosophila, with a focus on feeding, courtship, and aggression. These studies shed light on the molecular and cellular mechanisms by which key drive neurons receive relevant input signals, integrate information, and decide on a specific behavioral output. We also discuss conceptual models for integrating these circuit mechanisms, distinguishing between those for homeostatically-vs non-homeostaticallyregulated motivated behaviors. We suggest that the ability to trigger persistence of a motivated behavior may be a feature of integrator or apex/command neurons.