Abstract
Neuropeptides function as central neuromodulators and circulating hormones that modulate insect behavior and physiology. Leucokinin (LK) is an intercellular signaling molecule that mediates many physiological and behavioral processes. However, the functions of LK associated with environmental stress and feeding behavior in the fall webworm, Hyphantria cunea, is little known. Our primary objective is to understand the function of LK and LK receptor (LKR) neuroendocrine system in H. cunea. In the present study, the results showed that LK/LKR are expressed at different developmental stages and in various tissues of H. cunea. A candidate receptor–ligand pairing for LK was identified in the larval transcriptome of H. cunea. In a heterologous expression system, the calcium assay was used to demonstrate that LKR is activated by HcLKs in a dose-dependent manner, with 50% effective concentration (EC50) values of 8.44–90.44nM. Knockdown of HcLK and HcLKR by microinjecting target-specific dsRNA leads to several effects in H. cunea, including feeding promotion, increase in resistance to desiccation and starvation stress, and regulation of water homeostasis. The transcript levels of HILP2 (except in the LK knockdown group), HILP5, and HILP8 increased, whereas those of HILP3, HILP4, and HILP6 decreased; HILP1, HILP2 (in the LK knockdown group), and HILP7 gene expression was not influenced after LK and LKR knockdown. Variations in mRNA expression levels in insulin-like peptide genes in the knockdown larvae suggest an essential role of these genes in survival in H. cunea. To our knowledge, the present study is the first comprehensive study of LK and LKR – from gene to behavior – in H. cunea.
Highlights
As the central neuromodulators and circulating hormones, neuropeptides orchestrate insect behavior and physiology
Considering the induction of HcLK and Hyphantria cunea leucokinin receptor (HcLKR) mRNA expression by starvation stress, we investigated whether HcLK and HcLKR gene expression in the systemic silence plays a functional role in organismal stress tolerance employing knockdown of HcLK and HcLKR via dsRNA microinjection
Leucokinin, a multifunctional peptide acting as a neurohormone and neurotransmitter, is primarily synthesized in the central nervous system (CNS)
Summary
As the central neuromodulators and circulating hormones, neuropeptides orchestrate insect behavior and physiology. The complex hormonal and neuronal regulatory mechanisms maintain the metabolic homeostasis, which balance the food intake, energy expenditure, and nutrient storage in insects (Murphy and Bloom, 2006; Baker and Thummel, 2007; Leopold and Perrimon, 2007; Woods and D’Alessio, 2008; Teleman, 2010; Dalamaga et al, 2013; Leucokinin Signaling in Hyphantria cunea de Araujo et al, 2013; Vogt and Bruning, 2013). Insect leucokinins (LKs) are multifunctional peptides acting as neurohormones and neurotransmitters, which regulate diuresis, sleep, metabolism, response to ionic stress, food intake, and taste responsiveness (Terhzaz et al, 1999; Radford et al, 2002; Al-Anzi et al, 2010; Cognigni et al, 2011; López-Arias et al, 2011; Kwon et al, 2016; Zandawala et al, 2018a,b; Yurgel et al, 2019). The LK neuropeptide regulates stress tolerance and metabolism in D. melanogaster (Zandawala et al, 2018a)
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