Insulin-like peptides (ILPs) are involved in multiple functions in invertebrates, including metabolism, reproduction, growth, immunity, behavior, diapause, and lifespan (Okamoto and Yamanaka, 2015, Biglou et al., 2021, Chowanski et al., 2021). Insulin signaling has been widely demonstrated as a signal for the cellular uptake of circulating hemolymph sugars, which in insects is principally trehalose (Leyria et al., 2021a, Leyria et al., 2021b, Matsuda et al., 2015, Wyatt and Kalf, 1957). ILP signaling is particularly well studied and understood in Drosophila melanogaster (Grönke et al., 2010, Biglou et al., 2021), yet ILPs in other insects also have a demonstrated role in regulating circulating sugars (Wu and Brown, 2006, Brown et al., 2008, Okamoto and Yamanaka, 2015, Xue et al., 2020). Typically, these absorbed sugars are converted to intracellular glycogen for ready use or into lipids for longer-term storage (Brown et al., 2008, Pooraiiouby et al., 2018). Comparatively fewer studies have investigated the role of ILP signaling in circulating sugars in Heteroptera, despite this suborder’s impact on human health (Leyria et al., 2021a) and agricultural production (Xue et al., 2022). In Rhodnius prolixus, knockdown of an ILP (Rhopr-ILP1) resulted in elevated hemolymph carbohydrates and lipids, particularly after a blood meal (Defferrari et al., 2016a) while knockdown of an insulin-like growth factor (Rhopr-IGF) reduced circulating carbohydrates and lipids (Defferrari et al., 2016b). In addition, increased expression of ILP, IGF, and the insulin receptor IR1 occurs as starvation in R. prolixus progresses, possibly to create a sensitized state that can rapidly respond to release of ILPs after a blood meal (Leyria et al., 2021b). Incubation of Rhopr-ILP1 or porcine insulin with fat body or ovaries (and injection, for porcine insulin) increased expression of trehalose-specific facilitated transporter (TRET) in these tissues, suggesting that this may be part of the mechanism by which insulin signaling regulates circulating trehalose in R. prolixus (Leyria et al., 2021a).

ILP precursors are synthesized as a single peptide consisting of a secretory signal peptide, a B-chain, and an A-chain interconnected by a C-peptide (Krieger et al., 2004, Okamoto and Yamanaka, 2015). Six consistently spaced cysteine residues form three disulfide bonds, joining the A- and B-chains. Further post-translational modifications occur by prohormone convertase cutting of conserved dibasic cleavage sites flanking the A- and B-chains (Brogiolo et al., 2001, Krieger et al., 2004, Okamoto and Yamanaka, 2015, Biglou et al., 2021). The two-chain structure, consistent spacing of cysteine residues, and occurrence of dibasic cleavage sites delineating the A- and B- chains are characteristic features of ILPs. Many insect ILPs are produced in neurosecretory brain cells (Broughton and Partridge, 2009), but for some species they can be expressed in other tissues, such as the fat body (Badisco et al., 2008, Okamoto et al., 2009, Mizoguchi and Okamoto, 2013).

The western tarnished plant bug, Lygus hesperus Knight, is a polyphagous pest insect distributed across western North America (Scott, 1977, Wheeler, 2001, Antwi and Rondon, 2018). It feeds on numerous field, fruit, and vegetable crops, causing significant annual losses (Hagler et al., 2016, Joseph and Bolda, 2016, Zalom et al., 2018). Due to changes in agricultural practices over the past three decades, namely, a decrease in use of broad-spectrum chemical insecticides and a switch to transgenic and classically selected plant varieties targeted at non-Lygus pests, Lygus spp. have become significant pests and present one of the more considerable challenges for insect pest management to date (Lu et al., 2010). Lastly, insecticide resistance to multiple chemistries in Lygus lineolaris (Snodgrass, 1996, Snodgrass et al., 2009, Parys et al., 2018, Du et al., 2024a, Du et al., 2024b) suggests L. hesperus could develop similar resistance as well, which jeopardizes current Lygus species control strategies that are dependent on broad-spectrum insecticides (Parys et al., 2017). Therefore, new insecticides with novel modes of action and more specificity to Lygus spp. are needed to provide management of these insects. Neuropeptides and other signaling molecules have been suggested as new mode of action targets for pesticide development (Audsley and Down, 2015, Nuss et al., 2015, Conley et al., 2015).

Transcriptomes of L. hesperus suggest that at least three putative ILPs may be expressed (Hull et al., 2021). In this study, the expression of the three ILPs (termed LhILPs) was characterized throughout development and in various tissues of the adult stage. Also, the knockdown of individual LhILPs was examined for its impact on the ability of L. hesperus to clear circulating trehalose from the hemolymph. This work demonstrates the hallmark functions of insulin signaling in L. hesperus and provides a foundation to explore other functions associated with LhILPs in L. hesperus.